Evaluation of CAD programs and interior redesign of SEP Band2 · Evaluation of CAD programs and...

Evaluation of CAD programsand interior redesign of SEP

Band2

Christina Grahn and Johanna Liljedahl

March 24, 2006Master’s Thesis in Computing Science, 2*20 credits

Supervisor at CS-UmU and TFE-UmU: Hakan GullikssonExaminer: Per Lindstrom

Umea UniversityDepartment of Computing Science

andDepartment of Applied Physics and Electronics

SE-901 87 UMEASWEDEN

Abstract

This master thesis evaluates two modules in the 3D modelling software Catia; Imagineand Shape, and Freestyle Sketch Tracer. If these modules are considered useful in thedevelopment of military vehicles they will be introduced in the design process at BAELand Systems Hagglunds. The modules were applied when redesigning the interiors ofSEP Band2, which from a usability perspective needed to be modified. Another goalwas to provide a realistic presentation of the vehicle and photorealistic images of theinteriors. The main conclusion is that Imagine and Shape would enhance the designprocess by speeding it up, and increase the richness in details from a photorealistic per-spective. Freestyle Sketch Tracer is found to be complicated to use and will not enhancethe design process in a way valuable for the company. Also, the new interior designwould make the working environment better for the people using the vehicle.

Key Words Evaluation, usability, photorealism.

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Preface

We are both students of the Master of Science program Interaction and Design atUmea University, Sweden. However, even though we are students of the same program,our advanced courses differ a lot. Johanna has focused on graphics processing andelectronics, and Christina has focused on Human-Computer interaction and psychology.However, we both have industrial design as breadth. We realised about one year beforethe master thesis that we wanted to do the project together, because we thought wewould complement each other in a good way.

When we applied for the master thesis, we wanted to work at LSH. Johanna had fortwo summers worked at LSH and she was familiar with the company and the modellingtools they are using. It is a modern company interested in design and usability, and thatis what attracted us to the company. Our supervisor Fredrik Burholm is an industrialdesigner at LSH and he knows how to implement both design and usability in the workprocess.

In this master thesis, Johanna has worked with photorealism and rendering of images.Christina has conducted the evaluation of the interfaces and performed the usabilitystudy. Together we have redesigned the interior of SEP Band2 and improved its usability.

This report is part of a master thesis project and is a requirement for a degree ofMaster of Science in Interaction Technology and Design.

Ornskoldsvik, December 2005

Contents

1 Introduction and Problem Description 11.1 Goal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 BAE Land Systems Hagglunds . . . . . . . . . . . . . . . . . . . . . . . 11.3 Task Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4 Methods and Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2 Catia, Imagine and Shape, and Freestyle Sketch Tracer 32.1 Catia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32.1.2 Different Modules . . . . . . . . . . . . . . . . . . . . . . . . . . 32.1.3 Parts and Products . . . . . . . . . . . . . . . . . . . . . . . . . . 42.1.4 Catia PDA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42.1.5 Comparison with Other Programs . . . . . . . . . . . . . . . . . 5

2.2 Imagine and Shape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.2.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.2.2 The Functionality of IMA . . . . . . . . . . . . . . . . . . . . . . 52.2.3 Comparison of Creation Methods . . . . . . . . . . . . . . . . . . 5

2.3 Freestyle Sketch Tracer . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.3.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.3.2 The Functionality of FSK . . . . . . . . . . . . . . . . . . . . . . 72.3.3 FSK at LSH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3 Evaluation Methods and Application 113.1 Types of Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

3.1.1 Heuristic Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . 123.1.2 Descriptive Analysis . . . . . . . . . . . . . . . . . . . . . . . . . 143.1.3 Formative Evaluation . . . . . . . . . . . . . . . . . . . . . . . . 153.1.4 Cognitive Walkthrough . . . . . . . . . . . . . . . . . . . . . . . 19

3.2 Evaluation of IMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213.2.1 Heuristic Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . 213.2.2 The Activity Theory . . . . . . . . . . . . . . . . . . . . . . . . . 25

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vi CONTENTS

3.2.3 Cognitive Work Analysis . . . . . . . . . . . . . . . . . . . . . . . 28

4 Photorealism 334.1 What is Photorealism? . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

4.1.1 Lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334.1.2 Details, Chaos and Imperfections . . . . . . . . . . . . . . . . . . 334.1.3 Arrangement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334.1.4 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

4.2 What Lighting Brings to Photorealism . . . . . . . . . . . . . . . . . . . 354.2.1 Different kinds of Light Sources . . . . . . . . . . . . . . . . . . . 364.2.2 Description of Light . . . . . . . . . . . . . . . . . . . . . . . . . 394.2.3 Shadows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 394.2.4 Colours . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 404.2.5 Positioning the Light Sources . . . . . . . . . . . . . . . . . . . . 42

4.3 Texturing, Materials and Surfaces . . . . . . . . . . . . . . . . . . . . . . 444.3.1 Diffusion, Specularity and Reflectivity . . . . . . . . . . . . . . . 444.3.2 Texture Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . 454.3.3 Typical Textures and their Digital Texturing Maps . . . . . . . . 474.3.4 Enhance Lighting with Shapes . . . . . . . . . . . . . . . . . . . 49

4.4 Photo Studio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

5 SEP 535.1 SEP and SEP Band2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

5.1.1 Description of the SEP . . . . . . . . . . . . . . . . . . . . . . . . 535.1.2 Evaluation of the SEP Band2 . . . . . . . . . . . . . . . . . . . . 535.1.3 Talking With the Users . . . . . . . . . . . . . . . . . . . . . . . 565.1.4 Changes Made in the SEP Band2 . . . . . . . . . . . . . . . . . . 59

6 Working with Catia and IMA 616.1 Working in IMA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

6.1.1 Working Method . . . . . . . . . . . . . . . . . . . . . . . . . . . 616.1.2 Together with Other Catia Modules . . . . . . . . . . . . . . . . 61

6.2 How to Make it Photorealistic . . . . . . . . . . . . . . . . . . . . . . . . 626.2.1 Divide the Part into Different Bodies . . . . . . . . . . . . . . . . 626.2.2 Add Details and Chaos . . . . . . . . . . . . . . . . . . . . . . . 626.2.3 Make Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . 646.2.4 Arrange and Use Perspective View . . . . . . . . . . . . . . . . . 646.2.5 Lighting and Shadows . . . . . . . . . . . . . . . . . . . . . . . . 656.2.6 Test Render . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 666.2.7 Render with High Quality and then Compress . . . . . . . . . . 66

7 Results 67

CONTENTS vii

8 Conclusions 698.1 Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 708.2 Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

9 Acknowledgements 73

References 75

A Eye Perception and the Gestalt Laws 77A.1 Eye Perception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77A.2 The Gestalt Laws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

B The Field Trip 79B.1 Questions Asked on the Field Trip . . . . . . . . . . . . . . . . . . . . . 79

C Images from the Redesign 81

viii CONTENTS

List of Figures

2.1 A part created in IMA, Generative Shape Design, and Part Design. . . . 62.2 A sketch in perspective view inserted in FSK. . . . . . . . . . . . . . . . 82.3 A sketch with the sketch parameter function, which is shown when a

sketch has been inserted in FSK. . . . . . . . . . . . . . . . . . . . . . . 82.4 Two sketches in FSK, placed right-angled to each other to be used as a

support when creating. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92.5 A screenshot inserted in FSK, which can be used as a support when creating. 9

3.1 Engestrom’s activity system, influenced by [2]. . . . . . . . . . . . . . . 153.2 The compass indcating which part that will affected by the modification. 213.3 The activated part, (marked in orange), will be moved when the green

compass is moved. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223.4 IMA workbench and Generative Shape Design workbench . . . . . . . . 233.5 An example of an error message. . . . . . . . . . . . . . . . . . . . . . . 233.6 Help text that is fully explaning. . . . . . . . . . . . . . . . . . . . . . . 243.7 Seatbelt holder created in IMA using the chair as a starting point. . . . 273.8 The chairs before and after adding material. . . . . . . . . . . . . . . . . 293.9 A part inserted in a product assembly to the left and the part alone to

the right. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303.10 The fire extinguisher before and after adding material. . . . . . . . . . . 30

4.1 Left) a parallel projection and right) a perspective projection . . . . . . 354.2 Ambient light makes the scene look flat and unnatural . . . . . . . . . . 364.3 A spotlight aims the light in a conical volume . . . . . . . . . . . . . . . 374.4 Highlights can be simulated with a point light . . . . . . . . . . . . . . . 374.5 A directional light give rise to parallel shadows. . . . . . . . . . . . . . . 384.6 With an area light windows can be simulated. . . . . . . . . . . . . . . . 384.7 The colour wheel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 414.8 Left) complementary colours give energy to the image and right) analo-

gous colours bring a harmonious feeling to the image. . . . . . . . . . . 414.9 A bed illuminated with only a key light. . . . . . . . . . . . . . . . . . . 42

ix

x LIST OF FIGURES

4.10 A bed illuminated with both key- and fill light. . . . . . . . . . . . . . . 434.11 Left) too many shadows and right) shadows erased. . . . . . . . . . . . . 444.12 A diffuse material illuminated with ambient light makes it hard to dis-

tinguish the shape of the object. . . . . . . . . . . . . . . . . . . . . . . 444.13 A specular and a reflective material have very different light reflecting

properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 454.14 The chair in left) and middle) have the same specularity value but differ-

ent roughness values and right) has a low specularity value . . . . . . . 464.15 A light bulb simulated with a totaly ambient mapping. . . . . . . . . . . 464.16 Transparency mapping on a see-through material gives shadows in the

scene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 474.17 Aluminium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484.18 Plastic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484.19 Oak . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494.20 Granite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494.21 Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 504.22 Chair fabric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 504.23 A smooth, rounded edge reflects the light in many directions. . . . . . . 504.24 Left) a sharp edge reflects light in an unnatural way, while right) a beveled

edge reflects the light more natural. . . . . . . . . . . . . . . . . . . . . 51

5.1 The exterior of SEP band2. . . . . . . . . . . . . . . . . . . . . . . . . . 54

6.1 The gun in a) is not divided into many bodies and can take only onematerial, while the gun in b) has many bodies and can take many differentmaterials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

6.2 The chair hooks, at the top of the image, look good from a longer distanceand not much time has to be spent in modelling them. . . . . . . . . . . 63

6.3 A close up requires lighting that brings out the shape . . . . . . . . . . 65

A.1 Figures of proximity, similarity, closure, and figure and ground. . . . . . 78

C.1 Instrument panel with three screens. . . . . . . . . . . . . . . . . . . . . 81C.2 Control buttons for the driver. . . . . . . . . . . . . . . . . . . . . . . . 82C.3 Mechanical meaters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82C.4 Steering wheel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83C.5 Close up on steering wheel. . . . . . . . . . . . . . . . . . . . . . . . . . 83C.6 Plastic cover hiding pipes. . . . . . . . . . . . . . . . . . . . . . . . . . . 84C.7 Floor covering cables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84C.8 Floor covering cables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85C.9 Floor in the back of the vehicle. . . . . . . . . . . . . . . . . . . . . . . . 85C.10 Weapon holder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

LIST OF FIGURES xi

C.11 Seat belt for the chairs in the back of the vehicle. . . . . . . . . . . . . . 86C.12 Four-point belt for the driver and the commander. . . . . . . . . . . . . 87C.13 A lamp, and an air controller for the soldier sitting in the right chair. . 87C.14 Head rest for the driver and the commander. . . . . . . . . . . . . . . . 88C.15 Head rest for the soldiers in the back of the vehicle. . . . . . . . . . . . 88C.16 Button for raising the driver’s chair. . . . . . . . . . . . . . . . . . . . . 89

xii LIST OF FIGURES

List of Tables

2.1 A list of Catia modules used in this master thesis. . . . . . . . . . . . . 4

8.1 The codecs that are installed on LSH’s computers and can be used forcompressing the movies . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

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xiv LIST OF TABLES

Chapter 1

Introduction and ProblemDescription

1.1 Goal

Nowadays the companies that make military vehicles deliver similar products when itcomes to technology and functionality. Therefore, to stand out on the market the com-panies have to start thinking in other directions. The area of design and usability is onesuch direction. Hence, it is desirable to find a good tool for quick and easy modellingof new and user-friendly products. BAE Land Systems Hagglunds (from now on alsoreferred to as LSH) wants to evaluate some of their tools to see if they are useful in thedesign process for the company.

When it comes to presenting products for clients, LSH can still improve their work.Currently the images and animations of the products are far from being realistic. Thiscan lead to unfavourable advertising for the company when other companies have betterpresentations.

1.2 BAE Land Systems Hagglunds

LSH has for long been one of the leading companies in developing military vehicles andfunctionality has been the biggest priority for many years. But as other companiesapproach LSH in functionality, LSH must find a way to stand out from the rest. Designand usability are important issues in this respect, which LSH has started to apply intheir development.

1.3 Task Description

This project focuses on evaluating design tools by redesigning the interior of one of thevehicles at LSH and present the interior in a photorealistic way.

1

2 Chapter 1. Introduction and Problem Description

1.4 Methods and Resources

By redesigning the interior of a vehicle at LSH the evaluations of the modules were made.To learn more about military vehicles and people using them, a trip to Boden was made.

When starting this master thesis project there was a prototype of SEP Band2 underdevelopment. When this prototype was built, the priority was to get the engine and theelectronics to work; its interior had not been evaluated from a user’s perspective. Inorder to know the users experience of military vehicles in general, and to see how theyuse the vehicle, a trip to Boden and I19 was made. From this trip a list of things toredesign and add to the interior was made and used to provide a new design. The toolused for the redesign was Catia, which is a 3D modelling program. The parts used tobuild a 3D model of the prototype were found in a database at LSH called Catia PDA.

Chapter 2

Catia, Imagine and Shape, andFreestyle Sketch Tracer

2.1 Catia

2.1.1 Background

Catia is a CAD program used at BAE Land System Hagglunds for the developmentand production of new concepts of military vehicles. Catia is developed by DassaultSystemes in France and is supplied at LSH by IBM in Sweden. Catia is a widely usedCAD program in the business of motor industry and product development. It is possibleto use Catia in the complete development process, from product concept specificationsto a complete product, and it includes style and form design, mechanical design, and itmanages digital mock-ups.

The products that Catia is used for are many, reaching from the body of the vehi-cle, to batteries and screws. It is not the size of the model being created that makes aproduct big; it is the amount of details it contains. Therefore, it is not harder to createthe body of the vehicle than a chair. The more details the model contains, the moredifficult building it. The constructor creates the models by starting out from a drawingwith measurements of the desirable product. During the creation, the constructor canlook at the model from any view he or she wishes, since it is in 3D. The parts a vehiclecontains are drawn by different constructors from different departments, the electricdepartment for instance is in charge of parts such as cables, batteries, and instrumentpanels.

2.1.2 Different Modules

Catia consists of many different modules, all with different functions. While modellingin Catia the users switch between modules to get all the functions necessary to makea complete model. Hence, it is the same product or part that is shown in the differentmodules. One module is used to design a shell to proceed from, others to measure thedrawings, or to create other details such as holes and cuts, and there are several othermodules. In Photo Studio, that will be presented in section 4.4, it is possible to setlightning and build a presentation set for the models that can be used to render pictures

3

4 Chapter 2. Catia, Imagine and Shape, and Freestyle Sketch Tracer

and videos. Part Design is the module that is used today at LSH to build the basicmodel. In Part Design a sketch is drawn from the measurements of the model; this isdone in the sketcher workbench. Then the user goes back to the main workbench andthe model is shown. It is now possible to modify the model with either the Part Designmodule or some of the other modules in Catia. Generative Shape Design is a moduleoften used to modify the models. For a list of the modules used in this master thesis, seeTable 2.1. All the modules in Catia have a similar user interface but different functions.

Table 2.1: A list of Catia modules used in this master thesis.

2.1.3 Parts and Products

To get started in Catia, a new part or product is chosen. In a product, different partsare put together into an assembly to create a whole model, for instance apply seatbeltsto the chair and make a product of them together. A product cannot be changed unlessthe inserted parts are opened in a new window and changed there. It is possible to haveboth a window with the product opened, and at the same time work in another windowcontaining the new part inserted in the product. When the new part is modified, thechanges are visible in the product assembly. It is possible to change the material of aproduct, but then the whole product will have the same material. If the material shouldvary between the different parts in the product, the material must be applied in thepart.

2.1.4 Catia PDA

When a part or a product is created, it is checked into a database called Catia PDA.It does not have to be a finished product or part in order to be checked into the CatiaPDA, the products and parts are checked in regularly. The products and parts can bechecked out either for editing or reading. If it is checked out for editing and then checked

2.2. Imagine and Shape 5

in again, the new changed product or part overwrites the old version. If a product orpart is checked out for reading, it is possible to make changes on it without changing theoriginal model. This makes it possible for constructors and designers to put together hisor her own product, and change material and other properties as he or she prefers. Allthe users having access to Catia PDA have access to all models created in all modules ofCatia, as long as they are checked in. The different parts and products are put togetherin a module called Assembly Design, creating a whole product. This method has beenapplied in this work, while altering the interior of the SEP (see description of the SEPin chapter 5).

2.1.5 Comparison with Other Programs

Catia can be compared with programs such as AutoCAD and Pro Engineer. The proswith Catia are that it contains many different modules with different functions, someof them with functions that can be compared with different programs. Imagine andShape, which is evaluated in this project (described in section 2.2), can be comparedwith Rhino, a program for instance used at Designhogskolan in Umea, and Photo Studio(described in section 4.4) can be compared with Maya or 3D Studio Max.

2.2 Imagine and Shape

2.2.1 Background

Imagine and Shape (in the following referred to as IMA) is a module included in theCatia tool. It is not yet introduced at LSH, but will be if it contributes to the ease ofdevelopment. The primary purpose of IMA is to create models and allow the user toshape a model just as he or she likes. It has been compared with modelling in clay,because of the free shaping functionality.

2.2.2 The Functionality of IMA

The interface of IMA is consistent with the other modules in Catia. It has the samebasic functions as all the other modules in Catia. It is easy to search through the menussince they are organised consistently with the Microsoft interfaces. What differs IMAfrom the other modules in Catia are the icons that goes with the functions that arespecific for IMA. As stated earlier, IMA is a module for free shaping. Other shapingmodules in Catia, such as Part Design, shape using measures of a drawing. In IMA nomeasures are used, the shaping is arbitrary. The models created are only surfaces sothey do not contain a lot of information; therefore they are easy to work with.

2.2.3 Comparison of Creation Methods

The difference between creating in IMA and the way that it is done today in Part Designcan be described as:

– When creating in IMA the surfaces are placed under geometrical sets in the part.A geometrical set can be seen as a folder in a part, where surfaces and body ele-ments are placed. It does not matter if the surfaces are in the same geometricalset; they are still independent of each other. If the material or another feature of asurface is changed, it is only the feature of that particular surface that is changed.


It is also possible to change material of the entire geometrical set if desirable. Ifa surface has been modified in other modules than IMA, the updates are placedbelow the surface in the geometrical set, the new version is shown and the oldversion is hidden. (This is shown in Figure 2.1.)

Figure 2.1: The geometrical set Faste contains Subdivision Surface3, EdgeFillet6, andEdgeFillet7, where EdgeFillet7 is the latest version. The old versions that are hiddenare faded out; only the current version is visible.

– In Part Design the parts and products created are solid, and the different solidsare placed in a part body. Every part that is in the same part body is affectedif a change is made on one of the parts. Because of this, the part body is notequivalent with the geometrical set in IMA. When a solid is created it is auto-matically placed in the part body. Then, for every change made, the propertiesof the solids are updated in the part body. Hence, it is always the latest updatethat is active; the old version is hidden (see Figure 2.1, where Pocket1 is theonly property, except for the material, that is created in the part body). It is pos-sible to activate the old version by hiding the new version and showing the old one.

All the geomterical sets, the part body, and properties are shown in a specification tree.There is always a part body for each part no matter what module is activated, not only

2.3. Freestyle Sketch Tracer 7

in Part Design. If a part has been created in for instance both Part Design and IMA,both the part body and geometrical sets are shown in the specification tree, no matterwhich module is activated (see Figure 2.1).

2.3 Freestyle Sketch Tracer

2.3.1 Background

Freestyle Sketch Tracer (in the following referred to as FSK) is another module in Catia.Its function is to insert sketches to Catia (See Figure 2.2). The sketches can be drawnfor instance on paper, or on a computerised drawing table. If they are drawn on paperthe sketches must be scanned to the computer. The sketches are then used as a supportin the background when modelling in other Catia modules. Instead of having a drawingwith measurements to start from, the person modelling in Catia has the sketch that thedesigner has made.

2.3.2 The Functionality of FSK

To insert a sketch with FSK the function “Create an immersive sketch” is used. Whena sketch has been inserted, the next step is to place the sketch in the start view. This isdone with the sketch parameter function that pops up next to the sketch when a sketchhas been inserted (see Figure 2.3). If the sketch is drawn in perspective, the placementis done using the conical view. If the sketch is a planar 2D view, the placement is doneusing a cylindrical view. If the sketch is in 2D there must be at least two differentviews(see Figure 2.4), otherwise the modelling will be limited. The placement of thesketch is done using cubical lines or a square line as sketch parameters. If the sketchesare in 2D it is easier to use a line, the cubical lines are preferable for a perspectiveview. These lines set the starting-point for the modelling. It is however hard to placethese lines correctly; it requires that the designer has drawn sketches that have the rightdimensions and views.

It is also possible to insert a screenshot to use as a support. For instance, a screen-shot of a model made in Part Design can be inserted with FSK and used as a supportto create a part in IMA (see Figure 2.5). The part will then be created with correctproportions but not necessarily the right size. This way of working can be comparedwith the method described in section 2.2.2, where the part being created in IMA isopened in one window, and inserted in a product in another window to see if the size iscorrect. The sketches only supplies a support in the background, so once the placementof the sketch is finished the modelling in other modules can begin.

FSK supports modelling in IMA because it allows for free shaping. For Part Designthe FSK module does not work because of the missing measurements. It is possible toadd measurements to the drawing, but these would mostly function to set the propor-tions between the different parts in the model, not measurements of size and distance.

2.3.3 FSK at LSH

The module is easy to use if the sketches are drawn in planar 2D view, which makes iteasy to place the sketches correctly and the parts are relatively simple to model. But if


the sketches are in perspective view, the difficulty increases. It takes a long time to placethe guiding lines, and the more difficult the sketch is the more difficult the placementis. It also requires that the designer draws the sketches proportionally and correctly.The industrial designer at LSH, Fredrik Burholm, only sketches in perspective view. So,using FSK to insert sketches as support would take a lot of time for the constructor be-fore being able to start modelling. And, if the sketches were to be drawn in 2D instead,Fredrik Burholm or other designers would have a lot of extra work to do.

Among the modules that LSH has today (not including IMA since it is not introducedyet), there is no one where FSK would simplify the modelling process. FSK works besttogether with IMA because of its free shaping. But, even if IMA is introduced at LSHit seems unnecessary to introduce FSK; it does not simplify the design process.

Figure 2.2: A sketch in perspective view inserted in FSK.

Figure 2.3: A sketch with the sketch parameter function, which is shown when a sketchhas been inserted in FSK.

2.3. Freestyle Sketch Tracer 9

Figure 2.4: Two sketches in FSK, placed right-angled to each other to be used as asupport when creating.

Figure 2.5: A screenshot inserted in FSK, which can be used as a support when creating.

Chapter 3

Evaluation Methods andApplication

3.1 Types of Evaluation

To better understand the IMA module, three different evaluations have been conducted,all with different motives. The first is to evaluate the interface and its functions, whatis good and bad with it. The second evaluation method was chosen to get an idea ofhow the interface works today. The third is to get an understanding of how the interfaceshould work in order to suit the users. The users of this module at LSH are experienceduser of Catia, so they are not beginners of using CAD programs. To understand whatthe evaluations are about, a short description of each method has been written, followedby the evaluation itself.

First a heuristic evaluation was made to analyse the pros and cons with the inter-face, by using a checklist constructed by Jacob Nielsen. Then a descriptive analysiswas conducted using the methods of Activity Theory. The reason for the descriptiveanalysis was to get an idea of how the interaction between the user and IMA actuallyworks. Finally, a formative evaluation was conducted using the Cognitive Work Analy-sis method. The ground for making a formative analysis was to get an idea of how theinterface would fit in the creation process at LSH. A cognitive walkthrough was per-formed during the formative analysis to see how the users adapt to the new interface.The formative and descriptive evaluation are used because they complement each other.

The reason for choosing these particular analysis methods is that they are well suited forinterface evaluation. There is also another method, GOMS (Goals Operators MethodsSelections rules) which can be used to evaluate working conditions and work environ-ment. But GOMS is adapted to the evaluation of line work, working with tasks that arerepeated over and over. These tasks can be timed to see how long it takes to perform atask and what can be improved to increase work load and performance. Thus, GOMSis not well suited for our purpose. [8]

11

12 Chapter 3. Evaluation Methods and Application

3.1.1 Heuristic Evaluation

A heuristic evaluation is conducted by having an expert looking at an interface, andthereby trying to come up with a list of pros and cons with the interface. Nielsenhas constructed a checklist with ten general principles that can be applied to interfaces.These principles should be considered to be rules of thumbs rather than specific usabilityguidelines. [14]

Ten Usability Heuristics

The following paragraph discusses material from the references [13, 14]

Provide feedback The system should always keep users informed about what is goingon, this can be done by giving feedback within reasonable time. The hourglass is agood way to show that the system is working; by adding a text row saying what ishappening the feedback is furher strenghtened. Another good way to achieve quickfeedback is through direct manipulation. An example of poor feedback is when auser executes an incorrect action and nothing happens. Instead of doing nothingthe system should show the user that the action was incorrect by presenting anerror message.

Speak the user’s language The system should speak the users’ language, with words,phrases, and concepts familiar to the user. Icons and symbols can have differentappearances in different areas. Therefore, it is a good idea to combine a symbolwith a supplementing label. The label can then be changed depending on thepreferred language. The interface should also make information appear in a naturaland logical order.

Provide clearly marked exits An interface should not trap users in a situation fromwhere there is no obvious escape. Users often choose system functions by mistakeand will need a clearly marked emergency exit to leave the unwanted state withouthaving to perform too many steps on the way. The interface should also supportundo and redo, and there must always be a way to change a wrongly executedaction. For instance, the paint bucket in a painting program is often applied onshapes that are not closed, which leads to a screen overfilled with paint.

Be consistent Users should not have to wonder whether different words, situations,or actions mean the same thing. There should only be one way to achieve aparticular user action (beside short cuts and commands), and not several buttonscarrying out the same things since that would confuse the user. This also appliesto subsystems. The interface should also follow platform conventions, not have ageneral appearance that applies to all different platforms. Hence, the actions thatneed to be executed to perform a task on an interface should be consistent withactions of the other interfaces belonging to the same platform.

Recognition rather than recall Humans short term memory is limited, therefore auser should not have to remember information from one part of the dialogue toanother [11]. The users’ memory load can be minimized by making objects, ac-tions, and options visible. Instructions revealing the usage of the system should bevisible or easily found when the user needs them. This can be achieved by usingicons instead of having to go through a menu with file names when performinga task. It is easier to remember the function of an icon with a picture than it is

3.1. Types of Evaluation 13

to remember a long file name. An icon with more detailed pictures increases theuser’s memory load even more.

The user should not have to remember information from one part of the dia-logue to another. Instructions for use of the system should be visible or easilyretrievable whenever appropriate.

Provide shortcuts The features that make a system easy to learn are often too slowfor an experienced user to use [11]. Features such as short commands, unseen bythe novice user, may often speed up the interaction for the expert user such thatthe system can fit both inexperienced and experienced users. A novice user usesicons or chooses commands from the file list. Experienced users find this timeconsuming and therefore require shortcuts and short commands. Even better isan interface that allows users to tailor a personal template for frequent actions.In that way the users can control the level of expertise themselves.

Simple and natural dialogue Dialogues should not contain information which is ir-relevant or rarely needed. Each extra unit of information in a dialogue competeswith the relevant units of information and reduces their relative visibility. Whenit comes to putting names on the icons, short text messages are preferred, the textshould not be longer than the size of the icon. Instead of simply matching theicons and symbols to the structure of the interface, they should be matching theorganisation of the users’ tasks.

Provide good error messages Error messages should be expressed in plain language(no codes), precisely indicating the problem, and constructively suggest a solution.A user should not have to wonder what the message means; it should be clear fromthe text what was wrong with the performed action. And the message should notonly state what was wrong, it should also contain a suggestion of how to solve theproblem. It should also inform the user about what application the error messageapplies to.

Error prevention Even better than good error messages is a careful design whichprevents a problem from occurring in the first place. There are two ways ofeffectively doing this, either eliminate error-prone conditions, or check for themand present users with a confirmation option before they perform the action. Theproblem described earlier about the paint bucket could have been avoided witherror prevention. Good error prevention here would be if the system informed theuser that the shape is not closed and therefore it would be a bad idea to use thatfunction. This would especially help the novice user of the interface, but it wouldalso make an experienced user attentive of what he or she is about to do. Since anovice user is not yet familiar with the interface, or the undo command available,he or she would not know what to do in such a situation. It is possible that theuser instead deletes all the work and starts from the beginning or panics and startsclicking other buttons, which in turn makes the situation worse. When the userfinally finds the undo button it is the new action that will be undone instead ofthe previous.

Help and documentation Even though it is better if the system can be used withoutdocumentation, it may be necessary to provide help and documentation. Any suchinformation should be easy to search, focused on the user’s task, list concrete stepsto be carried out, and not be too large.


3.1.2 Descriptive Analysis

To get an understanding of the interface, a descriptive analysis has been conducted usingthe Activity Theory. According to Nardi, the activity theory is a powerful descriptivetool since it offers perspective on human activity and concepts describing it [12].

The Activity Theory

The following paragraph discusses material from the references [2, 12]

The intention with the activity theory is to understand interaction between conscious-ness and activity. The theory focuses on analysis and design for a particular workpractice where qualifications, work environment, and division of work is of concern. Italso involves analysis and design with focus on actual use and the complexity of activitywith several users, and particularly the conception of the artefact as a mediator is im-portant. The development of expertise and of use in general, active user participationin design, and focus on use as part of design, is also analysed.

The activity theory offers a set of perspectives on human activity, and a set of con-cepts for describing that activity. Tools, different ways of distributing work, standards,and language are all seen as artefacts in the activity. They are made by humans and theymediate the relationship between people and material or products at different stages.The basic principles of the activity theory include objects, mediating tools, a hierarchicalstructure of activity, internalising-externalising, and development.

Activity hierarchy The activity theory analyses activities directed at a particularobject. Activities consist of goal directed actions which must be taken in orderto fulfil the motive. Behind the motive is a need, which the activity responds to.The activities are conscious and different actions can be performed to reach thesame goal. They are implemented by automatic operations, which do not have agoal of their own, but offer an opportunity to adjust the actions to the currentsituation. The activity theory says that the constituent parts of an activity canchange if the circumstances do.

Object Human activity is directed toward an object that is about to change. Anobject is something that objectively exists in the world and can be studied withobjective methods. It can be things or humans, theories, models, or social orcultural phenomenon.

Internalisation-Externalisation The activity theory separates internal activities, whichis human cognition that takes place in the human mind, and external activities,which takes places outside the body. The activities cannot be understood if theyare analysed separately, since they transit into one another. The transition be-tween internal state and external state, or vice versa, is called transformation.The internalisation is the transformation from external activities to internal, andoffers an opportunity for humans to try potential interaction with the surroundingworld without really manipulating real objects (mental simulations, conceptions,consider alternative plans and so on). Externalisations transform internal activitiesto external, and are often necessary when internalised actions must be repaired.Externalisation is also important for cooperation between several people when itrequires that their activities are performed externally in order to be coordinated.


This constant transformation can be seen as the base for human cognition andactivity.

Development The transformations between internal and external states can be a prod-uct of changes in the environment or changes of a person’s abilities or conditions.The transformations can be caused by breakdowns and then lead to development,which is a good thing.

Mediating tools The activity theory indicates that human activity is mediated throughtools, tools that shape the way people interact with reality. If external activitiesare shaped, the internal activities are also shaped. The tools reflect the experi-ences of the users which can be the physical properties of the tool or the knowledgeof how the tool should be used. The tools can be either physical or psychological.It is the situation that decides whether an artefact works as a tool that mediatesthe activity or is an object of the activity. This affects the external behaviour andthe mental ability within the individuals. Engestrom’s activity system is a goodtool to use to analyse this mediation (see Figure 3.1).

Figure 3.1: Engestrom’s activity system, influenced by [2].

3.1.3 Formative Evaluation

A formative model is “a model that describes requirements that must be satisfied sothat a system could behave in a new, desired way” [19, p.7]. Formative analysis is away to get an understanding of how an interface could be designed to function in themost productive and effective way. If the structure of the work can be understood,suggestions of changes can improve the work radically. The goal with formative analysisis to build a structure in the interface that naturally supports a user through his or herwork. The structure should also be flexible enough to allow new ways of working. [19]The formative analysis will be conducted using the concept of cognitive work analysis.


Cognitive Work Analysis

The cognitive work analysis consists of five phases, which are shortly described below.The phrases are work domain analysis, control task analysis, strategies analysis, social-organizational analysis, and worker competencies analysis.

Work domain analysis (WDA) The following paragraph discusses material fromthe references [16, 17, 19]

In this phase the work domain itself is analysed, and with this it is meant theobject where actions are executed. The structure of the controlled system is de-scribed independently of the workers, automation, events, tasks, goals or interface.The work domain consists of a set of physical and intentional restrictions whereactivity develops, but it does not describe the activity itself. Intentional means thereasons why a technical system exists and has to be controlled. A WDA involvesan analysis along two dimensions, abstraction and decomposition. The abstrac-tion levels range from the most abstract to the most concrete level of form, wherethe higher levels represent the work domains functionality and purpose, and thelower levels represents its more physical implementation. There are five abstrac-tion levels to look at; functional purpose, abstract functions, generalised function,physical function, and physical form. Decomposition involves breaking down thewhole work domain into its existing parts. This can independently be performedat each level of abstraction since each of these levels describes the whole system.Hence, a work domain analysis defines the physical functionality and intentionalstructure of a work domain.

Control Task Analysis (CTA) The following paragraph discusses material from thereferences [16, 17, 19]

“A control task should identify what needs to be done, independently of howor by whom, using a constraint based approach” [6, p.183]. CTA and WDA com-plement each other. A work domain analysis describes the functional structure ofthe system, and in this phase one defines what goals to achieve for a work domainto be controlled, i.e. what goals are to be achieved. It is possible that the samegoals can be achieved in different ways on different occasions. To provide for thisvariability, an input-output analysis is required. This analysis identifies what in-puts are required to perform a task, the outputs achieved after it is completed,and the constraints that must be taken into account in selecting the actions re-quired to achieve the task. A CTA provides tools for identifying how control taskscan be executed. In order to do this, Rasmussen’s decision ladder is often used.The decision ladder is a template of steps that allow the controller, whether itis human or automatic, to take information about the systems state and fromthat act accordingly. When one of these steps in the decision ladder is produced,it receives inputs that consist of events, goals, and system states. These inputsare then transformed into outputs. However, the mode of procedure is left open.Hence, a control task analysis suggests what needs to be done, but not how or bywhom.

Strategies Analysis (SA) The following paragraph discusses material from the ref-erences [16, 17, 19]


In this phase an analysis of how a control task can be performed is made. Thefocus is on strategies and their actual demands, unconcerned with whom or whatis carrying out the strategies. Rasmussen (1981) defines a strategy as “a categoryof cognitive task procedures that transforms an initial state of knowledge into afinal state of knowledge” [19, p.9]. Thus, a strategy is a sequence of operationsthat takes the user from one place to another. A control task can be performedin many different ways and all with different costs and benefits. The differencescan depend on variability in the system, but also on individual differences in be-haviour, both across users within a situation and within a user across situations.Different people may prefer to perform the same task in different ways, but eventhe same person can prefer to perform the same task in different ways on differentoccasions. A strategic analysis strives to identify the different ways task goals canbe achieved. A way of describing the different categories of strategies is by usingan information flow map. The components used to construct flow maps should bespecific for the context surrounding them.

Social-Organisational Analysis (SOA) The following paragraph discusses materialfrom the references [16, 17, 19]

This phase involves looking at how the responsibility is divided among humansor between humans and automation, and how they all communicate and cooper-ate with each other. How work is divided and coordinated among actors deter-mines the information available for individual actors and that must be exchangedbetween them. If one group of actors is responsible for a certain level of abstrac-tion in the work domain, then the information included in that level defines theinformation content that should be presented for that particular group. The divi-sion and coordination of work is a dynamic process. Rasmussen has identified sixcriteria for dividing work demands [19]:

– Actor competency: Actors have different education and experience, andthereby different competency.

– Access to information or action means: Actors who have the most directaccess to certain information should be responsible for decisions associatedwith that information.

– Facilitating the communication needed for coordination: In some applicationswork demands requires coordination of several decisions or constraints. Insuch cases, it would be a good idea to distribute the responsibility for thedecision or constraints to one actor or a group of actors.

– Work load sharing: When the demands are too great for a single actor tocope with, it is a good idea to distribute work across actors.

– Safety and reliability: Redundancy can be built into the organizational struc-ture to improve safety or reliability. Two people are more reliable than onesince one person can detect a mistake made by the other.

– Regulation compliance: There could be a regulation that constrains howroles can be distributed across actors. This could shape the organizationalstructure.

These criteria are not independent of each other; on the contrary, decisions abouthow work should be divided can be controlled by several criteria.


Worker Competencies Analysis (WCA) The following paragraph discusses mate-rial from the references [10, 19]

The objective of this phase is to analyse what competencies the workers needto have in order to perform best. The persons using interfaces are of many dif-ferent backgrounds, with skills expanding from novice users to expert users. Theskills, rules, and knowledge taxonomy provided by Rasmussen is a modelling toolthat can be used to perform an analysis of the worker competencies.

The skills, rules, knowledge taxonomy

The users can be divided in three different levels of expertise using the skills, rules,knowledge taxonomy.

Knowledge based behaviourAt this level, all the actions are deliberately performed and based on a clear rep-resentation of the goal. The user starts with identifying the task, and makes adecision based on the appearance of the goal. In contrast to rule based behaviour(see below), the goals are clearly considered. This level calls for conscious atten-tion. The users on this level are so called novices or first-time users. They canbe either first-time users that know little of both the task and the interface con-cepts, but also experts that know the task concept but have little knowledge of theinterface concept. The users are assumed to know very little of what operationsthat can be performed. It is therefore important that the interface supports theuser by offering help texts and dialogue boxes to help guide the novice in the rightdirection. Another important support is the availability of online help, which isa tutorial with detailed descriptions of menu choices and icons. For a novice orfirst-time user it is good if the number of steps performing an operation is reducedto as few as possible, so that a task is executed in a shorter time. This way anxietyand frustration can be reduced; instead the user’s confidence is boosted. And, fora user of this level to know that the correct operation has been performed, it isessential that he or she receives informative feedback. The error messages providedwhen a user makes a mistake should be constructive, not critical. At this level ofexpertise the user can feel attacked if the error messages are critical and feel likehe or she are worthless because of the mistakes they made, and therefore developa recentness towards the system.

Rule based behaviourAt this level the user has stored rules that are derived from previous actions. Theseare presented in experience, the user knows what a specific action can achieve butare not thinking of these goals as they follow the rules. The goals can only befound in structure of the rules. When users are at this level of behaviour they arenot reasoning, they are just using familiar perceptual concepts of the environmentto trigger their actions. In contrast with skilled based behaviour (described be-low), users at this level are aware of their actions and can explain what they aredoing and why. Here the users have significant knowledge of the interface concept;


they know what to do, but must be reminded of how. The interface looks familiarand they need to be reminded of what to do next. It is important for these usersthat actions are performed consistently and frequently for them to rediscover howto perform their tasks correctly. By offering sequences of help messages, and ac-tions and guides to frequent patterns of usage, the users at this level will simplyrediscover how to correctly perform their tasks. Help embedded in the context areof great usefulness for these users, as well as well organized reference manuals.

Skill based behaviourThe actions at this level are smooth and automated, and are performed withoutconscious attention. Skilled based behaviour is usually composed of expected ac-tions, instead of waiting for something to happen and then react. Here the userscan be considered experts of the task being performed. They are frequently usingthe interface and perform their tasks at a quick rate. At this level, a user require arapid response time, brief feedback (just enough to know their command has beenexecuted), and, importantantly, short cuts for their most frequently used com-mands. An expert user seeks to reduce the number of steps to perform a task inorder to diminish the workload and save time. This can be supported by offeringa possibility to design a personal template.

An experienced user has no difficulty moving between these levels depending onthe work situation and often does this.

To get an aprehension of users skills, a cognitive walkthrough can be performed.

3.1.4 Cognitive Walkthrough

The following paragraph discusses material from the reference [14]

Cognitive walkthrough is a usability inspection method that focuses on evaluation ofa design, for instance the design of an interface. Cognitive walkthroughs focuses on easeof learning. Functionality and ease of use are correlated with ease of learning. If thefunctionality of an application does not match a users needs, the system will be difficultto learn to use.

A good way to see if a design is user friendly is to observe users using the interface.In the cognitive walkthrough, the test persons evaluate an interface by performing oneor more specific user tasks. The walkthrough amounts to performing a sequence ofactions in order to complete the designated tasks, which are decided by the evaluator.For each action, the evaluator tells a story about a typical user’s intention with theinterface. The evaluator asks how the user would do and what actions are available withthe interface. If the interface is good, the user’s intention should cause him or her toselect the appropriate action. By following the action, the interface should provide goodfeedback indicating that the task is about to be completed.

There are two phases of the cognitive walkthrough analysis; a preparatory phase andan analysis phase. In the preparatory phase, the evaluator decide on the conditions forthe walkthrough; tasks, actions sequences, and which users to use in the evaluation. Inthe analysis phase the main work takes place. The details depend on how the evaluator


will use the walkthrough. A walkthrough can be performed at different stages of de-velopment; on a paper simulation of the interface or on a prototype constructed with,for instance, Visual Basic, or on a fully functioning product of the design, as it will bein this evaluation. The walkthrough can be performed either individually or groupwise(this analysis will be individual).

The tasks analysed should be sampled from the basic operations which the systemis supposed to support. Also, tasks that require combinations of the basic operationsshould be included. These tasks should be as realistic as possible, including the neces-sary context, which should reflect the typical conditions under which the systems willbe applied. For each task, there should be a description of how the user should view thetask before learning the interface. There should also be a description of the sequenceof actions that should accomplish the task with the current interface. These actionscan be simpleactions such as “move the cursor to the zoom button”, or sequences ofseveral simple actions that can be executed as a block, such as “create a cube and applymaterial”.

The analysis phase of the walkthrough consists of examining each action of the solutionand attempting to tell a credible story explaining why the expected users would choosethat action. Those stories are based on assumptions about the user’s background knowl-edge and goals, and on an understanding of the problem solving process that enablesthe user to guess the correct action. The problem-solving process holds that users:

– start with a rough description of the task they want to accomplish,

– explore the interface and select those actions they believe will accomplish the task(or parts of it),

– observe the interface reactions to see if their actions had the effect they desired,and

– determine what actions to take next.

Users often use a “label-following” strategy, which means they select an action if thelabel for that action matches the task description. For instance, if the task is “createa cube”, the user probably selects an action labelled cube or an icon showing a cube.The critical features of the interface are those providing links between the user’s taskdescription and the correct action, and those providing feedback indicating that theperformed action moved the user one step closer to the goal. The evaluator shouldconsider the following four questions in order to evaluate the story of why a user wouldchoose the correct action at each step:

– Will the users try to achieve the right effect? For instance, if the task is to createa cube, will the user know that using the icon of a cube is the correct choice?

– Will the user notice that the correct action is available? If the action is to selectfrom a visible menu, there should be no problem for an experienced user. But ifthe action is to click the cube icon three times in order to create the cube, theuser will probably not think of it.

– Will the user associate the correct action with the effect being achieved?

3.2. Evaluation of IMA 21

– If the correct action is performed, will the user see that he or she is moving closerto the goal? For instance, after selecting the cube icon a cube appears on thescreen. If it does not appear, some feedback should indicate what was wronglyperformed.

3.2 Evaluation of IMA

3.2.1 Heuristic Evaluation

The user interface in IMA provides options suiting users from a novice level up to beingan expert. It supports most of the criteria listed above desirable for a user-friendlyinterface. The criteria lacking are important only for a novice user.

Provide feedback When opening a model in a Catia module there is feedback of thesystem working by a window showing how much is left before the model is down-loaded. This applies to all Catia modules when opening a model.

If a modification function is chosen and the cursor is moved over the model, partsof the model affected by the modification is highlighted (see Figure 3.2).

If the intentio is to move a part in a product, for instance to get the correctplacement, the compass is used. The compass is placed on the part to be movedand turns green when the part is activated (see Figure 3.3). If the compass iswhite it means that the part has been deactivated and the part will not move,only the compass. Also, when a part is activated it is shown by the parts name inthe tree being orange.

One drawback with the IMA that applies to all Catia modules is the fact thatif a function cannot be performed it is not certain it is faded out. It is not untilthe icon has been chosen and the dialogue box is shown that it is clear that theaction cannot be performed.

Figure 3.2: The compass indcating which part that will affected by the modification.

Speak the user’s language If a function has been chosen, a text explains the nextstep to perform, and this text is recurrent for every new selection the user choosesto make. Some of the functions are explained in words difficult to understand themeaning of, but this rather depends on a barrier of the language than strangechoices of words and phrases. Also, when moving the cursor over the icons, a text


Figure 3.3: The activated part, (marked in orange), will be moved when the greencompass is moved.

with the name of the icon and its short command is shown.

One drawback is that the only language is English, there should be a way tochange it to the language the user prefers. But this is something that applies tothe complete Catia program, not only to IMA.

Provide clearly marked exits If the user chooses the wrong function, it is possibleto leave that state by simply clicking the same icon again. For a novice user ofCatia this can be hard to understand, but once this function has been discoveredit is easy to remember. In IMA, and Catia in general, there is always a possibilityto undo the last action provided that the user has not saved the work in between.There is also a possibility to use multiple undo. If this function is chosen, a list ofall actions performed is shown in a window. From there it is possible to choose theactions to undo, on one condition. The actions are placed in the order they areexecuted and must be undone in that order. The undo command can be performedusing the icon, but it can also be done with the short command “ctrl + z”. If theuser accidentally pressed undo too many times, he or she can choose to redo theprevious actions. But, as for undo, if the work has been recently saved the usercan only redo up until the saved program state.

Be consistent IMA is consistent with the other Catia modules. There are standardicons and functions that are possible to see and perform in all of the Catia modules,what changes are the workbenches. The workbenches are the tools placed tothe right of the interface (see Figure 3.4). If a user needs to work in differentworkbenches at the same time, he or she can choose to open them in the sameinterface. Also, it is only one icon or button for each tasks and all icons have aunique function. But, there is one icon containing different modification functionsreachable in two ways. One is by clicking the modification icon and the other isto double click the model indicating that changes are desirable.

Error prevention IMA offers error prevention to some extent. If the user is aboutto do something that is not allowed, the system tells the user that the actionabout to be performed is wrong. This is shown by a red help text that is nextto the cursor, saying why the action cannot be performed. However, if the user


Figure 3.4: A screenshot of the IMA workbench to the left, and the Generative ShapeDesign workbench to the right. The icons to the right in each window are the iconsdiffering between the workbenches.

has chosen to remove the help text, the error message cannot be seen until heor she has performed the action. If an action has been wrongly performed, theuser gets an error message saying that the action cannot be performed and why(see Figure 3.5). In IMA, some of the faulty actions can be avoided by using thepreview option which is available for the styling surfaces icons. These are functionsfor changing parts of the surfaces of the model, by either cutting faces, erasingfaces, or extruding faces. There are other modification icons but these do notcontain any sort of preview function, instead the user has to execute the actionand then undo if it was wrong. The user can also choose to use multiple undoif many actions were wrong, but this calls for some level of experience with theinterface.

Figure 3.5: An example of an error message.

Recognition rather than recall IMA provides the user with well designed icons,clearly indicating their functions. These functions can also be reached by go-ing through the menu searching for the correct command name or using a shortcommand. If the user has forgotten what actions a certain icon can perform, he orshe can retrieve this information by using the Catia help, which is easily reachablefrom the help menu at the top of the page. The dialogue box appearing whenmoving the cursor over the icon reveals the name of the icon which can enhancethe memory enough to remember its function.

Provide shortcuts There is a short command associated with every icon provided bythe IMA interface. The zoom, rotate, and pan functions that are standard forall Catia modules, and frequently used in IMA, are reachable by using differentcombinations of the mouse buttons. An experienced user of interfaces in Catiaalmost never uses other commands than short commands, and IMA is not different.IMA also provides the option of creating a personal template. If there are certain


commands that are frequently used, the users can easily create their own shortcommands facilitating the work further. If some of the short commands providedby IMA are difficult to understand, the users can simply replace it with their own.

Simple and natural dialogue In IMA, the icons do not contain any text messages.Instead, if a user moves the cursor over the icon and holds it there for a second,the name of the icon is presented in a separate dialogue box along with a shortcut command if there is one. The icons are named in a way revealing the functionof the icon, which is good. Also, when pointing at an icon, a text message of howto execute the action is shown in the bottom left corner. It says what to do, andwhat short command to use if preferred.

Provide good error messages The error messages provided by IMA are written inEnglish and in complete sentences, but they are not always constructive. Some ofthe messages can be hard to understand the meaning of. It is easy to understandthat the action performed was wrong, but when it comes to interpreting why itwas wrong it is hard to understand exactly what should be done to prevent themistake. This depends of course on the level of expertise of the user, for a noviceuser messages are difficult to understand, but for an expert user the message wellexplains what is wrong. However, some error messages, like the one shown inFigure 3.5 above, are detailed.

Sometimes, if an action has been performed incorrectly, the model turns red,which in our culture indicates stop or danger. But it is still possible to move onand execute another action, which is strange. If the model suddenly turns red, orchanges into a colour it has not had before, it should indicate that something iswrong. There is no error message that goes with the colour change indicating itwas a wrongly executed action.

Help and documentation Catia provides the users with an online help found underhelp in the menu at the top of the interface. This help contains clear explanationson how to use the different icons provided by each module. There are picturesenhancing the explanations making it easy to understand how to proceed.

It is possible to choose the amount of help wanted while using IMA. The usercan choose to have help text next to the cursor explaining every step that needs tobe done in order to work with the model using a certain function. This text can befully explaining, little explaining or removed, depending of the users preferences(see Figure 3.6). For a first time or novice user it can be a good help to havean explaining text next to the cursor easily showing what is possible to do withthe chosen icon. However, if the user is an expert user this much help is redundant.

There is also always a text at the bottom showing what possible commands thatcan be executed.

Figure 3.6: Help text that is fully explaning.


3.2.2 The Activity Theory

The activity theory analysis provides a description of how the IMA module works andhow it is used.

Activity hierarchy

– Activity: The main activity for the user is to create models and concepts that areused in the development of military vehicles. This is done in Catia using differentmodules, where IMA is one of them.

– Action: The user working with the IMA module and the interaction with otherCatia modules. To get a good result of the model it is preferable to switch betweenthe modules, though it is possible to create a complete model using only IMA.

– Operation: Shapes and figures are built by using the functions of the IMA interfacetogether with the other Catia modules. First a shape to start from is chosen. Thenthe modification of the model begins by using the modification tools in IMA, orswitching to another module in Catia that has the desirable action. If the modelcreated in IMA is to be inserted in a product assembly, it is a good idea to do thisbefore the model is finished to see how it affects the whole product.

Object The objects in question are the models that can be created with the Catiamodule IMA. The models created with this module are more freely shaped, whichis different from the other modules, because they are not based on measures as inother modules (Part Design for instance). Instead, the models are created freelywith the creator setting the properties of its appearance. The appearance of themodels can be inspired from sketches or shaped from imagination. The modelscan be shaped to improve the appearance of an existing model, contributing tothe wealth of details in a product assembly, or simply as a model of its own. Themodels are only surfaces, which makes them less heavy for the computer to process,compared to the solids created in other modules. However, it is possible to applymaterials the same way as for models created in other modules.

Internalisation-Externalisation The internal activities are the ideas of models thatare found inside a persons head while creating in IMA. The external activities arethe shaping taking place on the computer screen, the hands using tools as computermouse and keyboard to create, and the use of sketches or images to get ideas forthe creation. The concepts developed are constantly switching between internaland external presentations since the user has an idea of a model in his or herhead while creating the model physically using IMA. This idea can change as themodel takes form, new ideas emerges as the appearance changes. When creatinga model it is possible that something goes wrong, perhaps an executed action isfollowed by an error message and the shaping wanted fails. Then a breakdownbetween internalisation and externalisation appears. This breakdown then leadsto development, and the next time the person knows that way of carrying the taskout was wrong.

Development The users of IMA are constantly learning and develop experiences thatwill lead to faster creation of models; there is no limit of how much a user can learn.When first using the module, there can be some difficulties with the functions andicons, since they are new for the user. If the user has experience in other Catia


modules there will be no problems learning this module as well. In order to getthe best results the user should complement the IMA module by using the othermodules in parallel. This way of working is not something new for an experiencedCatia user. The more experienced in Catia the user is, the faster the developmentof learning the module will be. If the user is a novice or first time user of Catia therewill be a long development phase before he or she can call themselves an expertuser of IMA. There are many functions to learn and many steps to remember eachtime a new model is created. But the more the user work with the interface, themore he or she will learn and constantly improve as a constructor.

Mediating tools An analysis of the mediating tools has been conducted using En-gestrom’s activity system (see Figure 3.1).

Subject The subjects of the activity are the users of Catia that will use IMAto develop models. Since IMA has not yet been introduced at LSH there is no wayof saying exactly who at LSH that will use the module as a daily tool. However,it is certain that the users of IMA will be persons already working with Catiaon a daily basis. IMA is a great tool to use to make models detailed, which is adesirable quality when making photorealistic pictures and videos (see chapter 4).Hence, it is possible that the users of IMA will be those employees at LSH makingthese pictures and videos. Also, persons interested in making products and partsmore detailed will probably be working with IMA.

Tools The tool analysed is IMA, a module of the CAD program Catia. Themodels created with this module are more freely shaped than models created withthe other Catia modules. The activity amounts to creating 3D models during thedevelopment process of military vehicles. IMA is best used in parallel with otherCatia modules to get the ultimate result, but it is possible to create a completemodel with this module. The models created in IMA are only surfaces, not solids,but it can still be used with Part Design, which can be used to make solids from thesurfaces. This can be a good procedure when creating pockets and holes, or if itis necessary to calculate the models density and measurements. Generative ShapeDesign is another module working well together with IMA. With this module theedges and corners of the surfaces can be bent, it is possible to create referencepoints, planes, and lines to create sketch planes from. Those sketch planes areused to make the pockets, holes, and other features in Part Design. A commonway of working is to switch between different modules in order to design a completemodel. If the model being created in IMA is to be inserted in a product assembly,it is a good idea to open the product assembly and insert the model before it isfinished. Then, as the model develops, the changes can be seen in the productassembly. In this way, the person creating has constant control of how a changeaffects the complete product in the assembly.

Object/Result The main purpose of IMA is to create 3D models with inspira-tion from sketches drawn by a designer, modifying existing products and parts, orto create them freely from mental models. The models in this module are morefreely shaped than models shaped in other Catia modules; the process can be com-pared with modelling in clay. It is easy to pull the models in different directionsto create the desired form. A good way of working is to use a product or partas a support to start out from and return to when creating in IMA. For instance,


the chair was used as starting point to create the seatbelt holders (see Figure 3.7).Working this way, the resulting model will get the correct properties.

Figure 3.7: Seatbelt holder created in IMA using the chair as a starting point.

Rules/Routines There are a number of rules to follow, Catia sets the rules for howthe interface works. All the modules belonging to Catia are edited with the samebasic structure, only the specific functions adherent to the particular module differbetween them. The rules and routines when it comes to designing are set by theparticular interface. When a user is designing in IMA there are certain steps thatare usually followed. They are not rules as much as they are routines. The firststep is to create the basis of the model, in that way there is something to relythe rest of the creation on. As stated earlier, if the part created in IMA is tobe inserted in a product assembly, it is a good idea to insert the basic modelin the assembly and at the same time also have the new part opened in the IMAmodule. In this way, it is possible to adjust the size to the products in the assemblyand change other features that do not fit. When the basic model is finished thecomplementary parts and details can be created. If the basic model is created aswell as all the complementing parts before checking if the size is correct, all thedifferent parts of the model must be resized one by one. It is difficult to do thischanging of each part equally.

Workplace The workplaces for the Catia users are varied. It depends on what depart-ment the certain user belongs to and at what part of the design process he or shebelongs to. But for the use of Catia it does not matter which department the userbelongs to.

The division of labour The users of Catia have different tasks to handle. They areworking with different stages in the design process and they model different things,therefore they have separate assignments. For instance, a person at the electron-ics department handles the assignments such as electronic cables, batteries, andinstrument panels.


3.2.3 Cognitive Work Analysis

This is a formative evaluation, which makes it a study of how the IMA module is like,who the users are and how easy they can learn the interface, how the interface is used,and an evaluation of what can be improved to enhance work environment and workingconditions.

Work Domain Analysis

The work domain is analysed to see how the IMA will contribute to the way of workingat LSH.

The IMA module and Catia in general is the considered work domain. The purposeof IMA is to allow more freely shaped figures and models, making it possible to createmodels much the same way as sketching on paper or modelling in clay. The abstractfunction of this module is to improve methods of working and the work environment.The constructor can easily create a model with IMA by having a paper sketch or apicture for inspiration, or create from imagination. As stated earlier, a common workprocess is to use the original models that are checked into the Catia PDA as support, andthen use IMA to modify the models to make them look more realistic. As generalisedfunction the focus is to make the modelling easier. The models created in this modulecan easily be modified, since the module provides the designer with easily changeablefeatures. Compared to Part Design (see section 6.1.2), where you have to enter thesketch to modify it, it is no problem to change the whole part even after it is insertedin the product assembly.

Control Task Analysis

By analysing the control tasks a way of working can be shown.

When creating in Catia in general, the constructor has a drawing with measures ofthe model to start out from. All the rounding of corners and edges, and holes and pock-ets created are created from measurements. The models created this way are straightand rigid, irrespective of what kind of model it is. A chair, for instance, will not havethe impression of being soft and comfortable to sit on. This is what differs IMA fromthe regular way of creating in Catia. With IMA it is possible to add details that makethe impression of, for instance, the chair to seem more realistic. There are no measure-ments to use in order to make a part rounder or angular; it is the imagination of theconstructor setting the boundaries.

To create a part in IMA, there are a few steps that need to be taken in order to obtainthe wanted model. First, a surface to start out from has to be chosen. This surfacecan be any of the possible surfaces supplied by IMA. For some purposes one shape ispreferable, for other purposes another. Secondly, the shaping and material choices takeplace.

Strategies Analysis

This part of CWA presents strategies that are good to consider before starting to createparts in IMA. This will contribute to making the method of working with the IMAmodule easier.


There are two ways of working in IMA, and both ways help enhance the wealth ofdetails in a model, which is good when making photorealistic pictures or videos (seesection 4). The first way is to use an original part from the Catia PDA and then modifythem. It is easy to make details and add these to, for instance, a chair. In this work acover to the chair has been made using the IMA interface. The chairs used today in thepictures of the SEP are grey and look like they are made of steel. When the cover to thechair was applied, as well as the correct material, they look very real in the renderedpictures. See comparison in Figure 3.8, where the original chair is to the left and themodified chair on the right.

Figure 3.8: The chairs before and after adding material.

The second way is to create a model from scratch and apply a part created in IMA in aproduct assembly. The creating with this strategy amounts to adding a part missing inthe product and in that way enhance the wealth of details. A good working method isto open the product assembly and insert the part, before it is finished, in the assembly(see Figure 3.9). This makes it possible to modify the part in IMA and instantly seethe changes in the assembly when switching to that window. In that way it is easy toget the correct size and shape of the part. It is not a must to insert the part in theproduct assembly before it is finished; it is possible to create the whole model first andthen insert it. But in that way it is not certain that the model fits where it is supposedto. It is easy to change the size of the part with one function, but if the part consists ofmany different surfaces they have to be resized one by one, and it is difficult to obtainthe exact same proportions with the new sizes.

Social Organisational Analysis

This analysis is done to see what IMA would do for the work organisation at LSH.

If IMA will be used in the design process at LSH, it would probably call for a changein the usual method of working. The collaboration between industrial designer and thepersons creating in Catia would then be closer, since the industrial designer strives tohave as realistic models as possible. Those who would be using IMA would probablybe those who create photorealistic pictures and videos. The parts of the model that arenot manufactured at LSH are things that are a good idea to create in IMA. Things like


Figure 3.9: A part inserted in a product assembly to the left and the part alone to theright.

the fire extinguisher and the chairs are not manufactured at LSH but are things thatcontribute to make a picture photorealistic. (See Figure 3.8 and 3.10)

Figure 3.10: The fire extinguisher before and after adding material.

Worker Competencies Analysis

This part of CWA is the most interesting. By analysing the users’ skills and experiencesand compare them with the way the interface is designed, it is possible to see if theysuit each other. A cognitive walkthrough of the IMA interface has been conducted tosee how an experienced user of Catia can handle the new interface. The users are RogerElfving and Hakan Eriksson, who are both consultants working at LSH.

The cognitive walkthrough

This cognitive walkthrough was conducted to see how two of the possible users handlethe functions of the IMA interface. The users are both daily users of Catia; hence theycan be called experts in Catia. They have never used IMA but will probably to do if


the module is introduced at LSH. The tasks are limited to performing a model usingthe most basic functions.

Walking through the actionsFirst an introduction of the interface was made so the users would acquaint themselveswith the IMA interface. A short description of the icons and their functions was given sothe users would have heard about them and seen them before the walkthrough started.Then they were allowed to test the interface by themselves for a while to see how itworks. After this the main analysis started. They where given pictures of the modelsthey were to create which they could look at along with the following instructions of howto perform the tasks. The instructions were to create two different head rests, havingpictures of them as support. For the headrest in the back of the vehicle the instructionswere:

– Start by creating a sphere to have as a starting out model.

– Then extrude the sphere to create the basic shape.

– After this is done, use the tools palette to modify the model into the right shape.Useful icons/functions are face cutting, translation, affinity, and attraction.

– Finally, add the desirable material.

For the headrest on the drivers chair the instructions were:

– Start by creating a cube to have as a starting out model.

– Then use the tools palette to modify the model into the right shape. Usefulicons/functions are face subdivision, face cutting, translation, affinity, and attrac-tion.

– Create the two rods that holds the headrest to the chair. This can for instancebe done by creating a cylinder as starting out model, then using affinity andtranslation to get the correct length and proportions.

– Finally, add the desirable material.

Results They both used the interface with ease, their experience of Catia gave them theconfidence to try new functions witout hesitating. They used the IMA interfacethe same way they use the other Catia modules; they tested a function and if itwas not the one they were looking for they just used undo. They quickly startedto use short commands when their functions were explained to them, like they doin the modules they usually work in. Even though it is a diffrent way of workingwith IMA than with other modules they still saw how they should create to getthe desired shape. They are used to switch between modules when creating andhad no problem with that in IMA either.

From the walkthrough the following conclusions were made:

Knowledge based behaviourThe users of IMA at LSH will be those who are experts of Catia in general. They knowwhat they would like to do. But they have little knowledge of this particular module.


Hence, it is important that the interface of IMA is user-friendly and supports the prin-ciples for good interface design. After working in IMA a while and testing the differentfunctions, the next level is reached. Since the users are already familiar with Catia ingeneral they will have no problem reaching the next level in a short time period. Thefunctions are familiar; it is only the workbench of IMA that is new. The general func-tions of the new workbench can take some time to get a grip of, but for an experiencedCatia user it will be no problem.

Rule based behaviourSince the users of these modules already have knowledge of Catia in general, they arefamiliar with the interface but not the particular functions and icons introduced in thismodule. The users will apply the same methods when using IMA as they are used toapply in the other Catia modules. The way of creating is no different from the otherCatia modules, and the switching between modules to receive the complete model isalso applied in IMA. It is possible to create a complete model with IMA, which is new.And the fact that the models created are only surfaces, not solids, is something newthat comes with IMA.

Skill based behaviourAt this level the users are experts of IMA and the actions are performed without con-scious attention. This level is reached after some training in the IMA module. It is notpossible to say a certain time period it takes to reach this level of expertise since thatis individual, but for a daily user of Catia it would not take long. Since those who willbe using IMA are persons that use Catia as a tool in their daily work, there will be noproblem to become experts of IMA as well. Perhaps the skilled based behaviour leveltakes some practice to reach, but the rule based behaviour level will be reached after abit of practice. A particular education to use IMA is not necessary, if a person can useother Catia modules he or she will also learn IMA. But, it can be a good thing to havea short introduction course to get the users started, just to learn about the icons andtheir functions.

Even if a user has reached the skilled based behaviour level, it is possible that he or shemeets obstacles with some tasks and moves back to a lower level. By moving back andforth between the levels, the user increases his or her knowledge of the IMA interface.The more difficult tasks solved, the more experience and knowledge the user will have.It is not a necessity at LSH that the users of IMA has a background of being a designeror an artist, the purpose of IMA at LSH would be to add details and products that canbe inspired by photos or sketches, or other Catia models that need modification.

Chapter 4

Photorealism

4.1 What is Photorealism?

Making a computer modelled scene look like a photo is what defines it as photorealistic,and to do that, a couple of things have to be considered. A photo is often very complex,containing a lot of information, light sources and structures. Often one can “read” thesituation from the photo, e.g., the time of the day, a cold winter day, party feeling, or afeeling of horror.

4.1.1 Lighting

The lighting has to be set to either bring out the shape of the object, or to establisha mood in the scene (see section 4.2 about photorealistic lighting). This does not onlyconcern the virtual scene, but also real world arrangements.

4.1.2 Details, Chaos and Imperfections

In real life we are surrounded by details, chaos and imperfections, so to set up a digitalscene that is flawless or lacking details would make the image look very unrealistic; theviewer would think that the image is too good to be true. One has to consider carefullywhat details are to be added to the scene. Details can show how a product is used orput together and sometimes they have to be there to make the image “possible”. If forexample something is screwed into the wall, screws must be added. Details also have tobe added to make the image interesting to look at, but also to bring attention to somepart of the image. Colours can be used in different combinations to bring energy or aharmonious feeling to the image (see section 4.2.4 about colour combinations).

4.1.3 Arrangement

When the scene is to be arranged, it first has to be carefully planned. If close ups are tobe rendered, a large amount of time and effort has to be put on the details. The detailshave to be well modelled, well arranged and melt into the environment. Lighting isoften done with three-point lighting because close ups often is about showing a specificproduct or detail. Images taken from larger distances need details too, but here timeinstead has to be put on the lighting and the arrangement of the scene. Details do not

33

34 Chapter 4. Photorealism

have to be well modelled, but they have to be in the right places. Lighting is often donewith light sources simulating real life light sources, such as sunlight and lamps. Imagestaken from large distances do not focus on one specific detail; they focus on the wholescene and the mood of the scene.

The Golden Section

The golden section ( =0,618 or approximately 4/6) is a number that is associated withbeauty. Often patterns considered to be well defined and beautiful are arranged by thegolden section. An image arranged by the golden section can have the object-in-focus atabout 4/6 of the screen width. One theory about the “beauty” property of the goldensection is that it balances chaos and order [6]. Even though there is no complete evidenceof its contribution to beauty, many artists and designers still use the golden section intheir work.

Another beautifying ratio is 1/3 and it is often used by artists and photographs tocreate an interesting chaos in the image instead of placing the object in the middle ofthe image.

Showing Directions and Relations

Often something is happening in an image or there are relations between objects inthe scene. If something is happening in one direction, the other direction becomes“dead” and it is uninteresting to arrange the image so the “dead” direction is shown.In Figure C.13 an image of an individual lamp and an air controller is shown. Thelamp and the air controller is for the soldier in the right chair and therefore it is best toarrange the image so the lamp and air controller are in the left part of the image andonly parts from the right chair are shown. If the lamp and air controller would be inthe middle of the image (which could seem appropriate because they are to be in focus)the viewer would not know which chair the lamp and the air controller relate to.

Perspective and Parallel Projection

When something is looked at from a very long distance (like the stars) the light rayscoming from that object are parallel when they hit the eyes. The light rays are projectedon the retina in a so called parallel projection making all parallel lines parallel in theimage (see Figure 4.1 left). Normally, things looked at are at finite distance from theviewer and the light rays coming from the object are not parallel; the projection is aperspective projection. Parallel lines on the object are not parallel in the image, insteadthey seem to come from a point in space at finite distance (see Figure 4.1 right). Becauseperspective projection is the most realistic projection, the digital scene should also beprojected with perspective projection to best simulate reality.

4.1.4 Materials

A well designed material can bring much photorealism to the image and if badly designedit can totally ruin the image. It is therefore important to get the material right. Everymaterial in real life has its own characteristics and the digital material should also havethose characteristics. See section 4.3 about material properties and how the materialsaffect the lighting. Because the real world is chaotic, materials that give rise to repeating

4.2. What Lighting Brings to Photorealism 35

Figure 4.1: Left) a parallel projection and right) a perspective projection

patterns (if not the material should have a repeating patter, like the floor in Figure C.9)should be avoided. This does not just concern material design, but also the arrangementof the products in the scene. If something is repeating, it will not look realistic.

4.2 What Lighting Brings to Photorealism

In real life, light is an important and complex factor for perception. The human eyecollects light reflected from objects in our surroundings and creates images of the ob-jects on the retina. How the light is reflected from the object’s surface tells us whatkind of surface it is, and from that what kind of object it is. If the road seen from thebreakfast table reflects a lot of light instead of absorbing it, one can from that tell thatit has rained and that the road probably is slippery. Light can also fool the mind. Ifsomeone is skiing downhill on a cloudy day there is a big possibility to fall, becauseslops and bumps are hard to distinguish in the snow on a cloudy day (see section 4.3.1about diffuse materials and ambient light). Light and material’s reflective propertiesare obviously also a very important factor for how one perceives the world.

Lighting modelled by a computer must simulate the very complex lighting in the re-ality for the digital image to look like a photo. Light must be reflected from the surfacesof the objects as it is reflected in real life. Lighting a graphical environment in theright way often adds as much photorealistic feeling to the image as if the product is wellmodelled. If the lighting is bad, the well modelled shape of the object may not evenbe distinguishable. Also, shadows can be at the wrong places, or not even exist, andimportant details are hidden in the background. Good lighting brings out the shape ofthe object, reveals important details and hides not so important details.

A well defined lighting can set the mood of the scene. The mood of the scene is whatfeelings the image evokes, for example the time of the day, a scary atmosphere, a sunnyday, or a focus on a specific detail. Even non-realistic lighting (light sources at non-realistic places, such as under a table or behind a curtain) can make a scene appearmore photorealistic because it gives it a feeling. This is called to give a scene a cine-matographic effect [1]. In real life movie making, lighting is also added to set a mood inthe scene. Light beams are cut to fit a specific pattern and objects are illuminated atplaces were they in a real life situation should be in the dark. An example can be whena bedroom scene is filmed and the light is out. If no light is added the scene would be


in the dark and nothing would be shown. If the lighting is done properly no one wouldthink about that the movie is manipulated.

In summary, lighting is done for two major reasons; to bring out the shape of theobjects in the scene and to establish a mood in the scene.

4.2.1 Different kinds of Light Sources

Ambient Light and Indirect Light

Most computer softwares add a specific amount of so called ambient light to the scenefrom the start. The ambient light determines the general level of illumination of thescene [9]. Ambient light is light illuminating everything in the scene equally much andwith the same colour (see Figure 4.2) [3, 9]. In real life this kind of light does not exist.Light is always emitted from a source and light illuminating areas that are not directlyilluminated from a light source is called indirect light. Indirect light is light reflectedfrom other objects like walls and ceilings. It picks up colours from the environmentand varies in intensity [3, 5]. Computer simulated ambient light is not perceived asrealistic. It looks flat and the shapes of objects are hard to distinguish. Ambientlight should therefore not be used when creating photorealistic images. If the softwaredoes not support indirect lighting, indirect light can be simulated with fill lights (seesection 4.2.5).

Figure 4.2: Ambient light makes the scene look flat and unnatural

Spotlight

A spotlight source casts light in a specific direction and volume angle. Light comingfrom a spotlight can be aimed in an optional angle, and the illumination can be adjusted(see Figure 4.3).

The softness (falloff) of the light is when and how the intensity of the light decreases.When using spotlights this value can be regulated to best suit the purpose of the light.With a fast falloff there is an impression of a nearby light source and with a slow falloffthe light source seems to be distant. Spotlights are the most commonly used light sourcesbecause they are flexible and can be adjusted for almost every situation [1, 3, 9]. Theability to direct the light from a spotlight on a particular object or detail is a well-knowntrick to put the object or the detail in focus in the image [1, 3]. In real life this is not


Figure 4.3: A spotlight aims the light in a conical volume

common, but it certainly makes the viewer concentrate on what is important in theimage and live the image (see section 4.2.5)

Point Light

A point light casts the same amount of light in every direction. It is often used to sim-ulate ambient light. Light rays coming from any kind of light source does not penetratesurfaces unless they are transparent, so often one point light is not enough to simulateambient light. Recall that, in section 4.2.1, it was explained that ambient light is notphotorealistic. A point light is more suitable for simulating indirect light than for ex-ample a spotlight because a point light casts the light in every angle [5]. It is often usedwhen simulating light bulbs or special specular effects [3] such as the shimmering effecton the photograph in Figure 4.4. The size of the shimmer depends on the distance fromthe point light source to the photograph, but also on the material properties, which willbe discussed later in section 4.3.

Figure 4.4: Highlights can be simulated with a point light

Directional Light

If a light source is placed at a very long distance from the illuminated object the lightrays that hit the object are almost parallel and give rise to almost parallel shadows.This kind of light source is called a directional light source [1, 3, 9]. In real life the suncan be seen as a directional light source. A directional light does not have a noticeablefalloff and therefore this value normally can not be changed when using a directional


light in the computer. Objects illuminated from this kind of light source all produceshadows in the same direction (see Figure 4.5) [3, 9].

Figure 4.5: A directional light give rise to parallel shadows.

Area Light

The light rays from spotlights and point lights all come from one infinitely small point.When using area lights the light rays come from an area and not just from a point [1, 3, 9].This kind of light source does not exist in real life, but it can simulate many real lifethings such as light coming from a window, fluorescent tubes, light bulbs and so on (seeFigure 4.6).

Figure 4.6: With an area light windows can be simulated.

Faking and Modelling a Light Source

All the light sources explained above can in the computer be modified to simulate anykind of light source. Objects blocking the light rays from for example a spotlight canchange the form and falloff of the light beam. A light beam can be projected througha transparent object creating a desirable colour and shape pattern (see section 4.3.2).In many softwares the shape of a spotlight can be adjusted to fit the wanted shape [1].The list is endless of how a light source can be manipulated to effect the graphicalenvironment. The problem is to find appropriate solutions without crossing the non-photorealistic line.


4.2.2 Description of Light

Intensity

A light’s intensity describes how bright it is. Often the intensity is modulated by thecolour of the light. Bright colours result in a higher intensity than dark colours [3, 9].In real life, the brightness or intensity of one light source can appear different in dif-ferent settings even though the intensity of that light source is the same in all settings.One has to have that in mind when lighting digital scenes where the intensity of a lightsource should look the same, independent of the light source settings [3]. The intensity ofone light source may have to be adjusted when other light sources are added or removed.

A light’s intensity decreases with the distance from the light source; this is called theattenuation of the light. In real life the illumination attenuates in a so called inversesquare pattern. The formula is Illumination = Intensity/Distance2. To model thisformula in the computer causes problems because the illumination never reaches zero,no matter how big the distance is. For the intensity to reach zero, the distance wouldhave to be infinitely large. The human eye does not detect illumination below a certainlow value, so the intensity can be cut off at an appropriate value when modelling atten-uation in the computer. Often for convenience, a linear model is used when modellingattenuation [3].

Softness

An important property of real life light is that it is often soft, creating not as sharpshadows as computer simulated light. Soft light looks as if it is illuminated from anearby or big light source, while hard light seems to come from a distant or small lightsource. Hard lights do exist in real life, for instance sunlight, but more often the lightis soft. To get a photorealistic effect in computer rendered images it is important to beable to simulate soft light. Indirect light (see section 4.2.1) is best modelled with softlight while direct sunlight is best modelled with hard light.

Colour

Real life light has a variety of colours depending on the light source. Pure white lightdoes not appear normally in real life and therefore it is important to slightly tint thelight when rendering photorealistic images. Different colour settings of the light cancreate different moods in the scene. For more about this, read section 4.2.4 aboutcolours. Indirect light (see section 4.2.1) that bounces from surface to surface picks upcolours from the different surfaces. This is called colour bleeding and is a very commonphenomenon in real life [3, 5, 9]. The more saturated the colour of the surface is, themore colour is picked up by the light [9]. Adding colour bleeding to the scene is a veryimportant step to come closer to a photorealistic image.

4.2.3 Shadows

The following paragraph discusses material from the reference [3].

If a shape of some kind is to be rendered, shadows are the most important proper-ties to get right. Well placed shadows bring out the shape of the object and badlyplaced shadows can totally ruin the look of the model. If no shadows are added, the


object will look flat and undistinguishable and if too many shadows are added, the scenewill look messy and important details are not in focus.

Shadows also put the object in a position in a scene, defining where the object is inproportion to other objects. In Figure 4.10 the shadow on the left is important becauseit shows that the bed is not in the air but on the ground. A shadow can reveal thingsthat are outside the field of view and it can make an object that otherwise would meltin in the background to be separated from the background.

What is a Shadow?

A shadow is an area that receives no or little illumination; either something is blockingthe light (cast shadow) or the area is not illuminated. It is only cast shadows that canbe put on or off and be manipulated in digital lighting. The shadow is darkest wherethe normals of the surface point in the opposite direction to the illumination.

Creating Shadows

Often shadows from the key light (see section 4.2.5 about key- and fill lights) are usedin a scene because the key light gives the sharpest and strongest shadows. The shadowsfrom fill lights can in most cases be turned off, otherwise the scene can look messy if itcontains many different shadows.

In most computer softwares the softness and the colour (umbra) of the shadow canbe set. A too bright or too dark shadow looks unrealistic. To make the shadow lighter,fill lights can be used. Shadows can be faked by letting a light source illuminate lightwith negative intensity. Another way to fake a shadow is to block the light with anobject that has the wanted shape.

Ray Tracing

To render shadows in a digital 3D scene, the method ray tracing is often used. Themethod is to find a path for a ray of light for every pixel in the image that is to berendered; from the camera, through the 3D space, reaching a light source or an emptyspace. The technique is to divide the camera view into points (pixels) according to theimage resolution, and then project a ray of light from every point into the 3D space. Thelight ray will bounce on the objects in the scene in an angle depending on the surface’sreflectance- and transparency properties. If the ray finally reaches a light source, thepixel from where the ray came from will be illuminated. If instead the light ray doesnot reach a light source, the pixel will not recieve any light and it will be a shadow.Note that the path is from the camera to the light source, and not in the opposite way.Otherwise, not all of the pixels in the image will get an illumination value; the numberof light rays from the light source would have to be infinitelly many to establish that,and it is not computationally possible.

4.2.4 Colours

A real life light source is almost never pure white (a perfect mix of every colour). Anindirect light (see section 4.2.1) that has bounced from surface to surface most likely


picks up colours from the surfaces, “bleeding” it onto the next surface (see section 4.2.2).Depending on a lights temperature, the light glows with different colours. A light bulbfor example, has a yellowish light and the sun a more blue/white colour. Different colourcombinations in a scene can bring a certain mood to it.

Complementary- and Analogous Colours

Complementary colours are colours that appear on the opposite side of each other onthe colour wheel (see Figure 4.7). Complementary colours enhance each other whenthey appear close to each other in an image. These colours can be used when a feelingof energy is wanted in the image (see Figure 4.8) [3, 4]. Examples of complementarycolours are red-green, yellow-purple, and orange-blue. If a detail in an image is impor-tant and should be accentuated, it can be illuminated with a light that is coloured witha complement colour to the colour of the rest of the image.

In contrast to complementary colours there are analogous colours, situated right nextto each other in the colour wheel. When using analogous colours in an image the im-age feels harmonic, homogeneous and natural [3, 4]. Examples of analogous colours areyellow-orange-red and purple-violet-blue.

Figure 4.7: The colour wheel

Figure 4.8: Left) complementary colours give energy to the image and right) analogouscolours bring a harmonious feeling to the image.


Warm and Cool Colours

Colours such as blue, green and violet give a feeling of coldness and distance. Red,yellow and orange are warm colours and give a feeling of closeness. If something in animage is to pop out from a background it can be illuminated with a warm colouredlight source. For the opposite effect, if something is to be in the background it can beilluminated with a cool coloured light source [3, 4, 5]. In real life, the sun is an exampleof a light source that can be both cold and warm. In the morning the sunlight is warmwith a yellowish / orange hue. In the evening the sunlight is cold with a bluish hue. Byadding cold or warm colours to computer simulated sunlight, the time of the day in theimage can be simulated.

4.2.5 Positioning the Light Sources

To bring out the shape and the true colours from a computer modelled object it is notjust enough to illuminate it with one high intensity light source. Different light sourceshave to be used at different distances and angles from the object and they must interactin a way that brings out what is important to show on an object. Different light sourcepositions and intensities lead to different moods in a scene (see below).

Key-, Fill- and Backlight

A light source illuminating the main part of the scene is called a key light (see Figure 4.9).A key light often has the highest intensity of all light sources and causes the sharpestshadows. Sunshine is a common real life key light. To emphasize more of the scene, oneor many fill lights with a lower intensity can be added. The fill lights can represent lightsources such as lamps, but also indirect illumination reflecting from walls and ceilings(see Figure 4.10). To separate the object from the background, a backlight can be usedilluminating the object from behind [1, 3, 9].

Figure 4.9: A bed illuminated with only a key light.

Key-to-Fill Ratios

The key light should have a higher intensity than the fill light. Depending on the ratiobetween the key- and the fill light, different moods can be expressed in the image. Ifthe ratio is low (almost as much fill light as key light) the contrast is low and the scenefeels bright and shimmery. If the ratio is high the contrast is high and the scene feelsdramatic and dusky [3].


Figure 4.10: A bed illuminated with both key- and fill light.

Three-Point Lighting - to bring out the shape

The theory of three-point lighting is that a key light, a fill light and a backlight areplaced to best bring out the shape of an object. The key light is placed slightly aboveand to the side of the camera. If the key light is placed too close to the camera (andtherefore at 90◦ angle to the object) the object can look flat. A key light should createthe sharpest shadows and therefore it should be placed 15-45◦ above the camera and15-45◦ to the side of the camera. To simulate indirect illumination or to just illuminatemore of the object a fill light can be placed in the opposite angle to the key light andat a slightly lower position. The fill light should be placed 0-30◦ above the camera and15-60◦ to the side (opposite to the key light) of the camera. Finally, to separate theobject from the background it can be of necessity to use one or many backlights. Thebacklights should be placed behind and above the object. If the backlight is placed soit illuminates straight into the camera behind an object the illumination can have novisible effect in computer graphics because the object is in the way of the light rays. Inreal life, dust and particles around the object make the backlight visible [3, 9].

Cinematography Lighting - to bring out the mood in the scene

The idea behind cinematography lighting is to “cheat” properties and positions of lightsources to establish a mood in the scene, and also to make an image pleasant to lookat [1]. One light source that is supposed to illuminate a certain detail can accidentallyilluminate another unwanted detail or give an undesired shadow. To be able to resizeand change properties of the light beam can be of big importance to maintain thedesired feeling in the image. The light beam from a light source used in cinematographymust have the ability to select an object, and it must be possible to change the shapeof the light beam. If a shadow is undesired (for example if the shadow falls on animportant detail), or has the wrong shape, it will be removed or reshaped to suit thepurpose. To make effects such as dust, mist, and colour patterns, light can be projectedthrough transparent images onto the object. Finally, the properties of the light suchas falloff, colour and intensity must be adjustable [1]. To model with light using thecinematography technique is to experiment and find good values for the composition.The key is to emphasize important things, and hide not so important things and createa specific mood in the scene [1]. In Figure 4.11 below there is an example (left image)of how a realistic shadow falls on the vase that is supposed to be the main detail in thescene and (right image) how the shadows from one light source is removed to create aless messy image and bring the vase into focus.


Figure 4.11: Left) too many shadows and right) shadows erased.

Above and Below Object’s Level

Placing the lights very high above an object or very low under the object can createeffects that make the scene appear scary and mysterious [1, 3, 5]. Depending on whatmood is wanted, high or low light sources can be added to the scene.

4.3 Texturing, Materials and Surfaces

4.3.1 Diffusion, Specularity and Reflectivity

A perfectly diffuse surface (also called a Lambertian surface) reflects incoming light inevery angle. Note that the word diffusion also can be used to describe light comingfrom every angle, diffuse illumination (also called ambient light that was described insection 4.2.1). The viewing angle does not have influence on the amount reflected lightwhen a surface is illuminated with diffuse light [7]. If a Lambertian surface is illuminatedwith diffuse light it can be hard to distinguish the shape of the surface because lightcomes from everywhere and is reflected in every angle so that no shadows are created.In real life many materials such as paper, snow, and dry paint are close to be diffuse.

In Figure 4.12 below, a perfectly diffuse surface is illuminated with diffuse (ambient)light and it is very hard to distinguish the shape of the object.

A perfectly specular surface reflects the incoming light in one, single angle creat-

Figure 4.12: A diffuse material illuminated with ambient light makes it hard to distin-guish the shape of the object.

4.3. Texturing, Materials and Surfaces 45

ing a highlight on the surface. If a specular surface is illuminated with a very small andconcentrated light beam, the highlight will only be seen if the viewing angle is the sameas the specular angle [7]. In real life, a mirror is the material closest to be perfectlyspecular. Specularity and reflectivity are two very different things. A specular materialreflects all incident light in one direction into a highlight, while a reflective materialreflects the surrounding environment [5]. A mirror is both specular and reflective. Seefigure 4.13 to see the difference between a specular and a reflective surface.

Figure 4.13: A specular and a reflective material have very different light reflectingproperties.

4.3.2 Texture Mapping

When creating digital textures, texture mapping is used. Different kinds of texturedmaps are put on top of each other to build a surface texture. Depending on thereflectance-, roughness-, specularity-, transparity-, and colour attributes, the light reactsdifferent when it hits the surface.

Colour/ Diffuse Mapping

Usually a colour map is created first in the texture producing step. A colour map, alsocalled diffusion map, or image map, defines the colours of a texture and how much ofthe colours that are reflected back when light hits the surface. A texture with a highdiffusion value reflects more of its true colour than a texture with a low value. Veryreflective textures, such as metals, have a low diffusion value, and the true colour of thesurface is poorly reflected. A colour map defines what colours and colour variations thetexture has and how much of the colours that should be reflected when light hits thesurface. The diffusion light can have a colour of choice. A colour map does not includeshading or highlights [3, 4, 5, 9]. In real life, no material is totally diffuse so a diffusionvalue under 90 percent is normally used [3, 5].

A colour map can be a photo, or an illustration, and it gives the material its colourpattern. The colour map can be mapped planarly, cylindrically, or cubically, and theway it is mapped depends on what kind of surface the material is to be mapped onto.

Specular Mapping

Specularity is the strenght of the highlights on a surface when the surface is illuminatedwith light. A specular surface illuminates the light in a concentrated beam [3, 4, 5,


9]. Water has a high specularity value and paper has a low value. A specular mapindicates how specular a texture is and how the specularity is distributed over thesurface. Different parts of the surface can be more or less specular than other parts.Dust on a shiny plastic surface gives the texture a low specularity value where the dustis. The size of the highlight is defined by a roughness value and not by the specularityvalue which sets the strength of the highlight (see Figure 4.14) [3, 4, 5].

Figure 4.14: The chair in left) and middle) have the same specularity value but differentroughness values and right) has a low specularity value

Ambience Mapping

A texture that has the same colour when it is illuminated by a light source as whenit is not illuminated, has a high ambience value. A self illuminated surface has a highambience value [3, 4, 5, 9], and usually the colours of the ambient light can be set.These kind of textures do not exist in real life, but changing the ambience value indigital textures can produce effects such as light bulbs (see Figure 4.15) or make anobject more visible without adding a light source.

Figure 4.15: A light bulb simulated with a totaly ambient mapping.

Transparency Mapping

Transparency maps describe a texture’s transparency properties. It specifies where thelight goes through the material, and how much light that penetrates the surface [3, 4,5, 9]. The colour of the transparent map can often be set in the computer. In additionto using it for transparent materials such as glass or plastic, transparency maps areoften used for creating shadow patterns in a scene. An object covered with the partlytransparent material is illuminated with light and a pattern is projected from the object.These shadows can be “faked” shadows from light shining through for example a foliage


and can produce a real life effect to the image (see Figure 4.16) [1, 3, 4, 5]. How the lightpasses through the surface is described by the surface’s refraction value. The refractionvalue states how much the light rays bend. If the value is over 100 percent the light raysbend in a wider angle and what is behind the surface looks larger [3].

Figure 4.16: Transparency mapping on a see-through material gives shadows in thescene

Bump Mapping

Every material in real life has some sort of structure. In the computer a structure can besimulated with a bump map. A bump map simulates a structure by adding highlightsto the surface but it does not model the bumps. A bump mapped texture looks like ithas a structure when it is actually smooth [3, 4, 5, 9]. When a bump map is created,the surface’s normals are modified to the consequence that the light hitting the surfacebounces in different directions. This gives a feeling of a rough surface. From the colourmap’s grey values the surface normals are changed so that dark areas give weak or nohighlights and bright areas give stronger highlights [9]. One has to remember that thehighlights are only shown when the surface is illuminated with a light source. Creatinga realistic bump map is often the most effective way to achieve a photorealistic texture.If the bump map is good the specularity map does not have to be so advanced.

4.3.3 Typical Textures and their Digital Texturing Maps

Metals

Metals are often very reflective, and have a low specular value (see section 4.3.2). Veryreflective metals such as aluminium and chrome have a colour map with a low valuebecause they reflect mostly the surrounding environment and not their own colour.Coloured metals such as gold and copper have a higher diffusion (colour) value andthe diffusion light is coloured in a suitable colour. Brushed metals must have a colourmap with a high value because they are not so reflective and displays most of theirown colour. On the contrary they are specular with a low roughness value. Metals areopaque (non-transparent) and no light penetrates the surface. See Figure 4.17 for anexample of aluminium.

Plastic

In contrast to metal, plastic is often not reflective at all, but it has a high specular value.The colour map has a high value and a distinct colour. Depending on if the plastic is


Figure 4.17: Aluminium ambience 0.25, diffusion 0.3, specularity 0.05, rough-ness 0.05, transparency 0, refraction 1.0, reflectivity 0.70

matt or shiny the specularity value differs. A shiny plastic has a high specularity valuewith a low roughness value and a matt plastic has a lower specularity value and a higherroughness value. Plastic can be transparent but does not have a significant refractionvalue. See Figure 4.18 for an example of plastic.

Figure 4.18: Plastic ambience 0.25 green, diffusion 0.8 green, specularity 0.8white, roughness 0, transparency 0.39 green, refraction 1.0, reflectivity 0.05

Wood

What characterizes wood is its structure and colour, therefore a bump map can beconvenient to use to bring out the structure of the material. An image of the wood isused for a colour map. The diffusion value is very high because all of the wood’s coloursare shown. Wood has almost no specularity or reflectivity (shiny wood is most oftenlacquered). Wood has no transparency. See Figure 4.19 for an example of oak.

Stone

Stone is a material that can be both specular and reflective, just specular or neitherspecular or reflective. Marble is a shiny sort of stone and has therefore a high specularityvalue, while granite is matt and has a very low specularity value. Stone materials havea structure and bump maps are often used for modelling stone materials. All the colourof stone is reflected back so the diffusion value is high. See Figure 4.20 for an exampleof granite.


Figure 4.19: Oak ambience 0.25, diffusion 0.9, specularity 0.03, roughness 0.03,transparency 0, refraction 1.0, reflectivity 0

Figure 4.20: Granite ambience 0.25, diffusion 0.9, specularity 0.05, roughness0.06, transparency 0, refraction 1.0, reflectivity 0

Liquids

Liquids are probably the most difficult materials to model because they are the mostvaried ones. They can be fully transparent (for example water) or almost opaque (forexample engine oil). The light rays reaching liquids break at the surface, resulting ahigh refraction value. Liquids have mostly a very high specularity value and a very lowroughness value which gives strong and concentrated highlights. They are reflective,but not as reflective as for example plastic. Water is colourless (The blue colour isthe reflectance of the sky) while other liquids such as Coca Cola c© are coloured. Thediffusion value can be set high for coloured liquids. Since liquids often are bumpybecause of turbulence in the environment, using bump maps is a good way to get theright highlights. See Figure 4.21 for an example of water.

Fabrics

Fabrics are just as wood, non-specular and non-reflective. They can be partly trans-parent with a high roughness value. Fabrics have a structure and therefore bump mapscan be useful. Fabrics have high diffusion values and an image is often used as a colourmap. See Figure 4.22 for an example of a fabric.

4.3.4 Enhance Lighting with Shapes

The shape of the object has a big influence to how the light reflects back to the viewer.The diffuse illumination is highest where the normals on the surface points in the di-


Figure 4.21: Water ambience 0.5, diffusion 0.08, specularity 0.7, roughness0.02, transparency 0.87, refraction 1.35, reflectivity 0.06

Figure 4.22: Chair fabric ambience 0.25, diffusion 0.9, specularity 0, roughness0, transparency 0, refraction 1.0, reflectivity 0

rection of the incoming light [3, 5]. A sharp edge changes the normals very quickly andtherefore the light is only reflected (so that a viewer can see it) if the normals point in thedirection of the light. A smooth edge (bevel) has normals pointing in many directionsand therefore the light is reflected back so the viewer can see it (see Figure 4.23). Inreal life, sharp edges are rare. Bevelling the edges when modelling an object makes theobject look more real life like and the illumination and the shading are more believable(see Figure 4.24).

Figure 4.23: A smooth, rounded edge reflects the light in many directions.

4.4. Photo Studio 51

Figure 4.24: Left) a sharp edge reflects light in an unnatural way, while right) a bevelededge reflects the light more natural.

4.4 Photo Studio

In Catia, the module Photo Studio can be used to set scenes with modelled objects,and light-, shadow-, and material settings. The scene can be rendered to create photo-realistic images. One can choose from different kinds of light sources and make realisticmaterials to put on the models created in other Catia modules (for example IMA).

In Photo Studio it is not possible to create bump maps, and depth effects (e.g., ob-ject in focus and a blurry background). This can be done in a module called PhotoStudio Optimizer, that LSH do not have license to use.

In Photo Studio, the shadows are rendered with ray tracing (see section 4.2.3 aboutray tracing).

Chapter 5

SEP

5.1 SEP and SEP Band2

5.1.1 Description of the SEP

SEP is a generic term of a series of military vehicles developed at LSH. All of the vehiclesincluded in the SEP family are based on modules, which means that they can be suppliedwith different roll modules giving the complete vehicle its specific characteristics suchas troop transport, cargo carrier, and ambulance. The purpose is the possibility ofplacing the different roll modules on both band- and wheel versions of the SEP withoutmodifications. SEP is constructed in a way resulting in conveniences for the crew andtransported staff. SEP Band2 (the vehicle evaluated in this work) is a vehicle driven byband. The crew module (the front of the vehicle) holds the driver and chief, and thetroop module (which is evaluated in this work) holds ten men. Figure 5.1 shows theSEP Band2.

5.1.2 Evaluation of the SEP Band2

Current Prototype

An evaluation of the SEP prototype was made to identify flaws in the design of thevehicle. The following is a list of things found to be badly placed or in need of redesign.

The instrument panel First of all, the buttons and controls having similar functionsare sometimes not placed next to each other. Most of the controls seem to berandomly placed depending on where there is a free spot. For instance, there aretwo different functions of track tightening. According to the law of proximity,objects close to each other are seen as belonging to each other (see Appendix A).Hence, if there are two buttons performing similar things they should be groupedtogether. There are two buttons on the instrument panel that raises or lowers thechairs. This function can just as well be placed on the chair instead, in that waythere will be fewer buttons on the instrument panel, which will give it a neaterimpression.

Also there is a screen with a multifunction display placed behind the steeringwheel; this placement is bad in two ways. First, the screen is hard to reach be-cause of the placement behind the steering wheel. Second, the display is impossible

53

54 Chapter 5. SEP

Figure 5.1: The exterior of SEP band2.

to see if the driver has chosen to drive with the hatch open, with the chair andsteering wheel raised. Some important functions such as revolution counter, tankmeter, and oil pressure meter, are all placed on the multifunction screen.

There is a request of having three to five screens placed on the instrument panel.These screens would display the environment surrounding the vehicle and help thedriver navigate. They should also work as a commando central for the chief of thevehicle, who is placed on the chair next to the driver. In summary, a redesign ofthe instrument panel is desirable.

The steering wheel The steering wheel is more like a control column for an air planethan it is a control for steering a vehicle like SEP. It is not ergonomic at all;there is no rest for the arms or hands while driving. The SEP will be used fordriving longer distances and driving it can be a great strain to the driver. Thefunctions placed on the steering wheel are frequently used functions, which makesit a good placement. There are functions for indicator, headlights and dippedlight, horn, track tightener (one of the track tightening functions are placed on theinstrument panel), and windshield wipers. However, not all of the most frequentlyused functions are placed on the steering wheel, which they should be. Thesefunctions are the second of the two track tightener, and air intake function. Hence,a redesign of the steering wheel is desirable.

Cables and cords There are a lot of cables and cords hanging from the ceiling, stickingout from battery holders, and from the instrument panel. They all contribute tomaking the environment messy and untidy. A messy environment increases thestress level for a person, and the small space increases this level further. Thiscan be attended by covers. The covers should also have the same colour as thebackground to contribute to a tidier environment.

5.1. SEP and SEP Band2 55

Bolts and screws The bolts and screws in the vehicle are in general metallic. This, aswith the cables and cords, makes the environment seem messy and untidy since theinterior of the vehicle is mostly white. If the screws and bolts would have the samecolour as their background material they would not stand out and it would enhancethe feeling of tidiness. The eye tends to distinguish objects first by colour [18, 20],and if the bolts and screws are different colours than the background they arebelieved to be different objects. Information can be displayed in different ways,making it easy or difficult to choose the correct action [15]. With fewer distractionsit would be easier to distinguish the objects that are important to be separatedfrom the background, for instance handles that opens hatches, fire extinguisherand similar.

Placement of chairs Today the chairs are placed with the opposite chair right in frontof the other. When the soldiers are seated they are facing each other, and theirknees touch. (This applies to a person at a normal height of about 180 centime-tres.) For a taller person it is even tighter to be positioned that way. If the chairsare to be moved 2-5 centimetres in the opposite direction on both sides this prob-lem can be avoided. Then the knees of the soldier would be placed in parallel withthe soldier sitting in front of him or her, and he or she can stretch their legs outas far as they prefer.

There are two footrests on each chair. The function of these is for the soldiersto quickly place their feet on in the case of a rough ride. If the chairs and footrestsare moved a bit on each side it will be easier to toss the feet up fast. Of course, thefootrests need to be placed so that the soldiers only have to toss their feet up infront of them, not to the side. This can be solved by having one of the rests in themiddle of the chair and the other to the left or right of the chair. This contributesto a more comfortable resting position.

Head rests There are no head rests on any of the chairs, neither on the drivers’ chairsnor on the back chairs. The SEP will drive in rough and bumpy terrain, which willcause the soldiers head to move around. The soldiers wear a helmet that is heavy,which makes the head even heavier and strains their necks further. The soldiersin the back of the vehicle travels positioned sideways, therefore their heads movesback and forth to the side. The head rests would have to be shaped like a U sothey have support for the whole neck. It would also contribute to a better restingposition. The drivers are seated forward; therefore the head rests on the drivers’chairs do not have to be shaped the same way as those in the back. Nevertheless,a head rest is necessary because of the shaking during the drive and the heavyhelmet.

Conclusions of the SEP Band2 Evaluation

The conclusion of the evaluation was that a redesign of the instrument panel and thesteering wheel was necessary. Also, a replacement of buttons is important to facilitatefor the soldiers to find the correct functions for the correct purpose. If the cables andcords are covered, it would contribute to a cleaner and less stressful environment for thesoldiers, likewise would having the same colour of screws, bolts, and their backgrounddo. The redesign and replacement of objects are diminutive compared to the differenceit would make for the whole, both in functionality and appearance.

56 Chapter 5. SEP

5.1.3 Talking With the Users

In order to see if the things noted in the evaluation are important, to really get an ideaof what the soldiers need in their daily work, and what they are lacking in their vehiclesas they are today, a trip to Boden and I19 was made.

The Field Trip

Before this trip an evaluation of the SEP prototype at LSH was conducted. From theevaluation several things where observed, (see notes above). From this observation a listof questions to the military was written (see Appendix B). It should be noted that thevehicles used in Boden, and in the Swedish military in general, is not SEP. The vehiclesevaluated in Boden are Stridsfordon 90, Stripbv 90, Epbv 90, and Lvkv 90. But, eventhough the vehicles are not the same, there where several things found that could alsobe applied to the SEP. Even better is that Sep is only in the prototype phase, thereforeit will be easy to attend to the things found in the evaluation. The things noted are thefollowing:

Driver’s seat The driver’s seat should be designed to be driven with the hatch down.It is possible to drive the SEP both with the hatch up and down, the chair andsteering-wheel can be adjusted up and down. Even so, it is most important thatthe vehicle is designed to be driven with the hatch down. If the condition of theenvironment outside the vehicle is so bad that the soldiers have to be shut in, thedriver of the vehicle must be able to reach all the buttons from the position theseat is in when the hatch is down. He or she must also be able to reverse thevehicle without raising the hatch. This has been solved by using cameras in theback of the vehicle and the picture showing on screens placed on the instrumentpanel.

Screens in the back of the vehicle The soldiers cannot see the outside terrain whilesitting in the back of the vehicle. Due to this fact and since the road often isbumpy and rough, travel-sickness is a common problem among soldiers in militaryvehicles. If the soldiers have a possibility to see the outside of the vehicle, thissymptom can be greatly diminished. Also it is a possibility that the soldiers areless disoriented in the outside environment if they have to leave the vehicle quickly.

Seatbelts and seats The drivers need good support for their neck and back since theyare travelling in a forward direction. While driving over rocks and other roughterrain they jog a lot back and forth, hence they need to be thoroughly strappedto their seat. To attend to this problem the use of four point belts to stabilisethe drivers is a good idea. In the vehicles evaluated in Boden there are only waistbelts, which does not support the drivers much. The belts only keep the driversfrom sliding of the seats; they do not keep them from falling forward and perhapsbang their head in the instrument panel or other objects.

The soldiers in the back only need a belt buckled in the waist because they travelseated sideways, and hence do not fall forward. When the soldiers have their mil-itary clothes and gear on they are very immobile. The belts today are not usedmuch. Instead of using automatically rolled in belts they hang loose from the seat.Also, the belts are buckled on the side of the seat which makes it hard for the sol-diers to reach while they have all of their gear on. It is hard to turn to the side


while wearing a protective west, combat west, under garments, and possibly alsoa rain suit or a snow jacket. They also intrude on their neighbour’s space whenbuckling or unbuckling their belt. Because of this the soldiers are not using theirbelts in the extension they should. If the belts are buckled in the waist insteadand are automatically rolled in, the soldiers would only have to move their armsbackwards to find their belt. This way the belt is always on the same place andthe soldier does not have to turn around to see where the belt is. Sometimes thesoldiers must quickly remove their belts. This can happen if they have to get outin battle or if the vehicle has gotten stuck in a waterhole. For such a situationit is important that the belt come off easily, which it does if it is buckled in thewaist. It is also a good thing if the belt is rolled in automatically since soldiershave many loose parts on their gear that can get stuck in a loose belt.

Objects on the wall No objects, such as holds and panels, can be directly screwed onthe ceiling. If a screw is just screwed to the wall and the vehicle is hit by a mineor similar, the screw and its holder will shoot away like a projectile in the vehicle.If the screw hit a person the impact of the screw will be as bad as if it was a bulletbeing fired at him or her. For this to happen, all that it takes is a high pressureat the vehicle body for this to happen; it does not even have to make a hole inthe body. Therefore, there can be no loose object in the vehicle, everything mustbe strapped. If the vehicle is hit all loose things take off like projectiles by thepressure.

Buttons and controls Some controls are easy to accidentally change the state of.Such controls need a cover of some sort. A grating can be a good solution; it hasto be enough of a gap for a hand with a glove to reach it. The most importantthing discovered with the buttons and controls is that those that have functionssimilar to each other are not placed close to each other. On the steering-wheel thecontrols handling the most frequently used functions should be placed. These arefunctions such as air intake, windscreen wiper, and track tightener. It is often darkin the vehicle while driving, so the driver should have easy access to the mostlyused functions. As it is today, the driver has to constantly press the buttons thewhole time it takes to adjust the track and air intake. Instead the driver shouldbe able to let go of the button while the track is adjusted, or the hatch for the airintake is opened or closed, and it should automatically stop when finished. Whilethe driver holds the button, his or her focus is for a long time taken from driving.It should be enough to press the button for tightening the track once and thenpress it again when it is tight enough, and the same thing for loosing the track.The same applies to the air intake. Most of the time the hatch is opened the wholeway, and it takes too much from the driver’s focus to press the button until thehatch is opened enough.

Lights The light used in the vehicle cannot be completely bright; this makes the soldierblind when leaving the vehicle into a dark environment outside. If the light insteadis green there will be a less adjustment for the eyes and it will not as easily beseen from the outside if light is leaking out from the vehicle. It is important thatall lights in the vehicle are connected to a function that shuts down all lights fromone source. There are warning lights indicating that something is wrong with forinstance the engine. These should be place at eye-level so the driver easily canobserve that there is something wrong.

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Pedals The parking brake could be applied by the foot, and loosened via a level withthe hand. This would take less space from the driver’s area. There should also bea plate for the driver to rest the left foot, which is not used during driving sincethe vehicle has an automatic shifting gear. This will provide for a better drivingposition, especially while driving a longer distance.

Cables Covers over cables is a good idea, they can easily be integrated to the ceilingby using covers with the same colour as the ceiling. The covers keep dirt away,and they keep the cables from being in the way or getting stuck in something andbreak. Hidden cables also keep the environment cleaner, which makes it feel morecomfortable.

Colours The colour of the ceiling should be light to make the vehicle seem bigger thanit is. Dark colours makes small spaces feel smaller and contributes to a feeling ofbeing shut in. The colour can neither be too bright nor too shiny, since that willreflect light and makes the eyes tired.

Heating and ventilation A good thing for the soldiers is individual air controls. Themain ventilation should be controlled from one source. If something happensoutside that makes the air dirty, one person should be able to shut all air supply.A heating control is best placed blowing air close to the floor, since heat travelsupward. There is a problem today with the soldiers having cold feet and a warmupper body while seated in the vehicle.

Placement of weapons Today the soldiers are holding their weapon in front of themor they are placed in holders in front or in the back of the vehicle, far from thesoldiers placed in the middle. The soldiers are sleeping holding the weapons infront of them, a solution that is not safe. If the soldiers have their weapon placedin the back or in the front and quickly must have them, it is difficult to reachthem when they are so far away. A good idea would be to place the weapon closerthe soldier, for instance in a holder between the seats. In this way the soldier caneasily reach the weapon and does not have to sleep holding it.

Seat placement Today the seats are placed with the soldiers facing each other andtheir knees touching while seated. If the seats on both sides are moved a fewcentimetres in opposite direction this problem can be solved. Then the soldierswould have more space for their legs. They would also be able to stretch theirlegs out in front of them without being in the way of the person sitting in front ofthem. It should also be a footrest on each chair. If a mine hits the vehicle formbeneath, they must quickly place their feet on the footrest to avoid the vibrationsthat originate from the mine to spread through the body. The footrest can alsocontribute to a more comfortable resting position. The chairs should also havea rest for the neck. This is good for the neck both during the tour because theneck tilts back and forth, but also for sleeping. The rest can either be inflatableor pulled up from the seat when needed.

Conclusions from the Field Trip

The field trip to Boden confirmed that the things noted in the evaluation of the SEPprototype has to be changed, and it gave some additional things to think about forthe redesign and replacement of objects. It also gave insight in travelling in a military


vehicle; it is a rough environment even travelling on a gravelled road. Further, the tripgave some ideas of things that can be added to the vehicle in order to simplify the useof weapons and how to get the soldiers to use seat belts.

5.1.4 Changes Made in the SEP Band2

The early evaluation of the current prototype of the SEP along with the field trip toBoden supplied with several things that needed to be changed (see section 6.1.3). Themost important things have been attended to in this work. Those things are as following:

Instrument panel There is a request of having at least three screens on the instrumentpanel, which takes up a great space from buttons. Therefore, the instrumentpanel has been redesigned with new placement of buttons. The placements ofbuttons have been considered with respect to their functionality. Buttons thathave a similar functionality have been grouped together, since objects that areclose together are believed to belong to each other (see Appendix A, proximity).Buttons that are connected with the engine have been placed near the driver, andare separated according to which engine they control. An extension to increase thespace for the button has also been made. On the extension has, except for buttons,mechanical metres of oil pressure and similar been placed. Buttons controlling aircondition and lighting, which both driver and passenger can control, are placedin the middle on the extension. Since the model that has been evaluated is onlya prototype there is no way of knowing every function and button that will be inthe final product. Therefore, there are only some of the buttons that are labelledwith icons.

Steering wheel The steering wheel has been redesign both depending on its presentfunctionality and on its appearance. The current steering wheel looks like thecontrol column of an air plane; it has no similarity with a regular steering wheel ina car, for instance. The new design of the steering wheel has been made consideringthe steering wheel of a car so that the drivers will recognise it and know how to useit. There are some buttons placed on the steering wheel, but not all of the mostfrequently used. Therefore, the most frequently used buttons are placed on thenew steering wheel in a way that makes them easy to use. Since it is often dark inthe vehicle, it is important that the most frequently used functions are close to thedriver, so the driver does not have to leave hold of the steering wheel every timehe or she has to use one of those functions. The current steering wheel is attachedby two pipes, which it can be moved up and down on. The pipes are blockingparts of the instrument panel, including the screens that are to be implementedon the instrument panel. With the new design of the steering wheel there is onlyone pipe, which is easily placed between two screens.

Covers for cables and cords The cables and cords hanging from the ceiling andsticking out from the instrument panel in the current prototype of the SEP havebeen hidden by covers designed in IMA. The covers protect the cables and cordsfrom dirt and wear. The covers have also been given the same colour as the back-ground walls in order to give a neater impression. There are a lot of cables andcords in the current prototype, many of them can be placed and bent differently inorder to be hidden by covers or under the floor. Since there is no way of knowingwhere all of the possible cables and cords will be, only the cables that are visible inthe Catia models have been hidden, either with a cover or by placing them under

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the floor. This can be used as guidelines for future work of the SEP and othermilitary vehicles developed here at LSH, to always try to hide cables and cords bycovers and other available objects.

Bolts and screws By giving the bolts and screws the same colour as their backgroundthe impression of the vehicle has improved further and now they go well with theirbackground. Before, there were grey or black screws and bolts on white backgroundand it enhanced to making the environment messy. It should be easy to distinguishbuttons and other objects from their background when wanting to use them, notmistake them with bolt and screws.

Weapon holder The vehicle has been equipped with weapon holders. The currentprototype has no place to put the weapons during the drive which was somethingdesirable that concluded from the user evaluation. The weapon holders have beenplaced to the right of the chairs on the right side of the vehicle, and to the left ofthe chairs on the left side of the vehicle. The holders do not take up a lot of spaceand are easy to place on another side of the chair if desirable. The placement nextto the chair makes it easy for the soldiers to grab the weapons when they needthem and it is safer to have them on a holder than holding them in front of themduring the drive.

Seat belts The seat belts in the back has been modified so they are be automatic rolledin. Without automation the belts are hanging from the chair and they are hardto reach with the whole gear on. The soldiers must only move their arms back abit to reach the belts, which now are in the same place the whole time. The beltsare also modified to be buckled in the middle instead of on one side. This way thesoldiers do not have to turn to one of the sides to unbuckle the seat belts.

Personal air intake and lights The temperature in the vehicle can vary betweenvery hot and very cold, depending on the surrounding environment. Since everyperson has their own opinion of how hot it or cold it is or should be, personal airintakes have been placed next to each chair. These air intakes can be closed fromthe instrument panel if necessary, but are otherwise controlled by the soldiers.There is also a personal light placed next to the air intakes. It is often very darkin the vehicle and if a soldier wants to have a light on he or she now can. Thelights are supplied with green light which does not leek out as much as white light,and they can be switched off from the instrument panel if necessary.

Head rests The drive, in SEP and military vehicles in general, is rough and soldier’sheads tilts back and forth. The helmet is heavy which makes it harder to keep thehead still. Therefore, the chairs have been equipped with head rests.

Chapter 6

Working with Catia and IMA

When working with big models in Catia, it is a good idea to use cache management towork with the cache system. That is to open the products as surfaces and not as solids,which takes less computer power. When working with a part in a product assembly, thepart is activated to be in design mode. This means that the part can be modified. If apart is in visualisation mode it can not be modified, only viewed. Thus, using the cachemanagement is recommended when working with parts and products that are big.

To avoid unnecessary large and complex models, only the parts or products that arereally needed should be included in the assembled model. If for example only the ex-terior of a vehicle is to be shown in a rendering, the interiors should not be in theassembly.

6.1 Working in IMA

6.1.1 Working Method

To create a figure in IMA a new part is chosen. Then the user chooses a surface tostart out from, where the surface depends on what shape the final model will have.The most common surfaces to start from are a sphere or a cube, because they are easyto modify. There are other surfaces such as pyramids, cylinders, and planar surfaces,such as squares and triangles, but these are rarely used. After the correct surface ischosen, the modification begins to create the desirable figure. When a part is finished,or whenever a usable result has been created, it is saved. Then it is inserted in a productassembly. If the part needs to be modified in order to fit the product, this is done in theoriginal part of the IMA module and not in the part inserted in the product. When thechanges are saved, the modifications are updated and visible in the product assembly.It is common that a part is created and inserted in the product to see if the size andshape is correct before any other modifications are made.

6.1.2 Together with Other Catia Modules

A common method of working is using IMA together with the other modules in Catia.The module most commonly used in parallel with IMA is Generative Shape Design. Inthis module properties such as edge fillet (rounding of corners and edges), symmetry

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(creating a mirrored copy of the model), and points, planes, and lines (used to refer to)are used to modify the model. Part Design is used mostly to create pockets and holesin a model. In order to work with Part Design the model must be changed to a thicksurface, which means that the surface becomes a solid. IMA is a good tool for increasingthe wealth of details of a model. This is desirable when making photorealistic picturesand videos in Photo Studio (see section 4.4).

6.2 How to Make it Photorealistic

Adding photorealism to a product using the IMA module can be done by using analready modelled product and making different changes on it according to a few stepsthat will be explained below.

6.2.1 Divide the Part into Different Bodies

Using different materials on a part will only be possible if the part is divided intodifferent bodies (see section 2.2.3 about bodies) or geometrical sets. If the part containsonly one body the whole product will take the same material and will therefore not lookphotorealistic. Compare the gun in Figure 6.1a with the gun in Figure 6.1b to see theimportance of a subdivided part.

Figure 6.1: The gun in a) is not divided into many bodies and can take only one material,while the gun in b) has many bodies and can take many different materials

To divide an already modelled part into different bodies is a very time consuming processand should be done in the modelling process from start by the constructor or the de-signer. Often the part has to be remodelled into different bodies and the “main” bodywill in the end be hidden. Each body can take one material and the bodies have tocontain parts that will have the same material. To make the process and the productmore flexible, all parts should be in different bodies. If the part is modelled in IMA, itis modelled with so called subdivision surfaces, and these surfaces can all have differentmaterials and do not have to be in different bodies or geometrical sets.

6.2.2 Add Details and Chaos

Parts modelled in Part Design are very exact and static. It is hard to make changes,such as to move and resize a model, because measurements have to be exactly stated andcannot be approximated. In real life nothing is ever perfect (see section 4.1.2 about theimportance of imperfection to achieve photorealism), and it is therefore more convenient

6.2. How to Make it Photorealistic 63

to use IMA to model photorealistic products. In IMA it is easy to form an approximatedsurface by dragging and stretching a point in a desirable direction. To randomly choosea point and manipulate it will result in a more photorealistic shape of the model thanto carefully choose a manipulation point.

A product lacking details is uninteresting and unnatural. To spend time on makingrealistic details on the product is probably the easiest way to achieve photorealism. De-tails make the image more interesting to look at. The hooks on the chair in Figure 6.2are modelled in IMA with three surfaces in one part.

Figure 6.2: The chair hooks, at the top of the image, look good from a longer distanceand not much time has to be spent in modelling them.

Each surface can have a different material if desired but in this case the whole part hasthe same material. If no hooks are added to the product, people would wonder how thechairs are hanging in the roof and the image would not look realistic for that reason.Even though the hooks are rather “badly” modelled (a close look reveals the unrealisticshape of the hook) they still look realistic from the distance the image is taken. It canbe enough to just add a slipshodly made detail than to not add the detail at all. Closeups demand more accuracy in the modelled detail. Time can be saved if the image isplanned from the beginning; how the arrangement is to be done and from what distancethe image is to be taken. Clearly it is unnecessary to add or put a lot of time into detailsthat are not shown or in focus.

In real life there are no sharp edges but almost every edge is bevelled (see section 4.3.4about bevels) and therefore no edge should be sharp in the digital model either. InGSD it is very easy to bevel edges and one can in this way achieve a certain level ofphotorealism in approximately no time.

In Photo Studio it is possible to put stickers on surfaces. Stickers can be created fromphotographs or illustrations and can give good photorealistic effects. However, one hasto be careful when copying trademarks and other copyrighted images because that isagainst the law.


Shadow and highlight effects such as the one in Figure 5.1 are easily created by addinga partly transparent material (the image can be created in Photoshop) on a surface infront of a light source. The light will shine through the surface and create shadows orhighlights in the scene.

When an object is to be rendered photorealistic it is not just the object that has tobe photorealistic but also the background and the surroundings. Modelling everythingin a surrounding takes a lot of time and it can also be very hard to model for exampletrees in a photorealistic way. The surroundings in Figure 5.1 are created from threeimages manipulated in Photoshop. The images are arranged so that no joints are shownand so the object can be placed realistically in the surroundings.

6.2.3 Make Materials

Probably the most important property to establish photorealism is to get the materialson the products right. To get the right material, one has to carefully investigate thereal material (or a material close to it) to see what characterizes the material. If thematerial has a pattern or a structure, a photograph of the real material can be usefulwhen creating the digital material. The photo has to be taken without flash; otherwisethe image will be brighter in the middle and darker in the edges. When materials arecreated in Catia, one image is repeated horizontally and vertically. If the original imagehas bright and dark areas, a disturbing, unnatural pattern will appear when the mate-rial is created. The software Photoshop has a couple of functions to simulate differentstructures such as fabric and tiles. The fabric on the right chair in Figure 3.8 is createdin Photoshop by adding a structure filter on a green image.

It can be a good idea to make a couple of test renderings of an object with the materialto see how the material behaves when it is illuminated by a light source. If the materialis specular, the highlights will only be shown if the material is illuminated with a lightsource (see section 4.3.1 about specularity).

All materials that are not supposed to be self-illuminating should not contain anyamount of ambience. This is because the material will look unnatural if it is renderedtogether with a material that is to be self-illuminating; for example a light bulb. Neitherit is realistic when a material reflects its entire true colour, so the diffusion value shouldnot be 100 percent, but slightly lower.

6.2.4 Arrange and Use Perspective View

The scene must be arranged so that what is to be in focus really is in focus. Thatdoes not explicitly always mean putting the object in the centre of the image. Insteadone can use the rule about the golden section described in section 4.1.3 to make theimage more interesting. If something is happening in one direction in the image (if forexample a fire extinguisher puts out a fire in one direction), that direction should beshown in the image. For realism, the objects in the scene should not be arranged tooexact; imperfection is much more truthful and it also brings energy to the image.

To display as much as possible of an object’s shape it is better to slightly rotate theviewing angle instead of viewing the object perpendicularly. It is also important to

6.2. How to Make it Photorealistic 65

use perspective projection (see section 4.1.3) instead of using parallel projection to bestsimulate normal viewing.

6.2.5 Lighting and Shadows

An appropriate lighting can bring out what is important in the image and the shape ofthe objects. Often one key light and a couple of fill lights are used (see section 4.2.5about key and fill lights). Every image that has a different camera view has to be illu-minated individually because the shadows and the reflected light depend on the cameraview (if not the light is ambient, then the camera view has no importance).

When an environment built from photos is used, it is common that shadows from objectsfall on the environment. This will look unrealistic because the environment is “flat” aswell as the shadows. This can be avoided by shutting off the shadows for the back-ground, but then no shadows (wanted or no-wanted) will be shown. Another trick canbe to arrange the light sources or the objects so that the shadows are not shown or toturn off the shadows from a specific light source.

If the environment is built from photos, often there are already shadows and high-lights built in into the photos. To make the object melt in in the environment the lightsources have to be placed to simulate the light sources in the photos. One then hasto have in mind that sunlight give rise to parallel light rays (and parallel shadows) sospotlights can not be used for that purpose. Instead so called direction light has to beused (see section 4.2.1 about direction light).

When a product is to be in focus (see Figure 6.3) three-point lighting is often usedso the shape of the product is shown (see section 4.2.5 about three-point lighting). Ifinstead a whole scene with a complete set of products is to be rendered, it can be a goodidea to set the light sources to simulate real and existing light sources, such as sunshine,light bulbs and lamps (see Figure 4.16).

Figure 6.3: A close up requires lighting that brings out the shape


6.2.6 Test Render

During the whole photorealistic rendering process it is important to do many test ren-derings. One rendering should be done for every change of parameters; if for example alight source is added or adjusted or if a material is added or adjusted. Test renderingsdo not have to be in full quality; renderings with lower quality do not take as muchtime or computer power as a real high quality rendering. The important thing is toinvestigate how the changes of the parameters affect the photorealism in the image.

6.2.7 Render with High Quality and then Compress

For most flexibility it is best to render the image with the highest quality and thencompress the file afterwards, instead of compressing the file (for example save the imagein JPEG-format instead of TIFF-format) while rendering. A compressed file can not bedecompressed (to get lost information back) so it is best to have a high quality imagethat can be compressed afterwards for the purpose of use.

Chapter 7

Results

The resulting images of the interior redesign of SEP Band2 can be seen in Appen-dix C. To read about the description and evaluation of the SEP Band2, the reasons forredesigning the interior, and how the redesign was done, see section 5.

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Chapter 8

Conclusions

Without the trip to Boden we would not have accomplished as good a result of the vehi-cles interior redesign as we have. It was difficult to imagine the working environment ofthe current prototype, so talking with the experienced people in Boden was very useful.It is important to let the users take part of the design process and since the Swedishmilitary is possible to use the SEP vehicle it is valuable to have their opinion of howthings should be placed in the vehicle. (It is however equally important that designersand constructors know what they are designing.) By redesigning the interior of SEPBand2, the IMA module was well tested. It was useful to have something real to designwhen learning the module; it resulted in learning the interface well and a design of theinterior of Sep Band2 that better supports usability. The importance of having thefuture users testing a prototype early in the design process should not be overlooked.They can contribute with a lot of ideas that can save a lot of time and money if theyare implemented before the prototype is finished.

The three different evaluation methods used were all useful, since they all provideddifferent knowledge about the interface. The heuristic evaluation provided good knowl-edge of the interface itself, and the different heuristics made it easy to see if the interfacewas user-friendly or not. It provided a description of the functions of IMA more than adescription of the function of IMA at LSH. From this evaluation we could see that IMAis consistent with the other Catia modules and it supports most of the properties foruser-friendliness.

The activity theory provided with a description of how the IMA works, and how andfor what it can be used. It is not possible to know exactly who would use IMA at LSH,but it is certain that it would be a person that regularly works with Catia. The activitytheory supplied us with a description of the working method that should be used whilecreating in IMA.

The cognitive work analysis gave a model of how the IMA module would fit in thecreation process at LSH. By having potential users testing the interface, we could seethat IMA would be a useful tool in the design process. They had no difficulty learningthe new functions and thought it was a fun tool to work with.

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70 Chapter 8. Conclusions

The FSK module is a tool that is too complicated to use compared to what it pro-vides to the design process. It takes a lot of time to learn to master the module, andthe way it should be used does not agree with the design method at LSH. It would takea restructuring of the design method, which already works. The conclusion is that it isunnecessary to introduce FSK at LSH.

To make photorealistic images, IMA is an easy and effective module to use when mod-elling the parts in the scene. The module Part Design is more static than IMA, thereforeit is easier to model chaos and imperfections with IMA, which make the products real-istic. When models are created for rendering and not for calculations (eg. calculation ofthe mass or strength of a product), it is more convenient to work with surfaces (IMA)rather than solids (Part Design) because surfaces do not require as much computerpower as solids and they are easier to manipulate.

8.1 Limitations

All images and animations should be rendered with the highest quality possible andthen compressed for the purpose of use; this can take a lot of time. To reduce therendering time, the window size of the animation or the image can be set as small aspossible. Often the movies are shown from a projector with resolution 1024x768. Onecan then afford to take down the window size; the movie will still be sufficiently large forthe viewers to see. The animations created of the SEP Band2, using the Photo Studiomodule, are very big (a 4 seconds long avi-movie can have a size of over 114 MB) soa compression of the movies has to be done afterwards. It is important to use a codecthat is distributed on all the computers on Land Systems Hagglunds so that everyonecan take part of the movies. The codec also has to make the file much smaller andstill maintain as much quality as possible. The software V irtualDub R© can be used tocompress the movies. A list of the codecs that can be used on LSH’s computers is foundin Table 8.1. For this assignment, the movies were compressed with the codec IntelIndeo(R) video R3.2.

The animations and the images that are rendered for LSH can preferably be used foradvertising new products that are not yet put together. The client can then see theproduct before it is manufactured and be part of the design process. Digital images areeasy to manipulate so only the information needed can be shown.

8.2 Future Work

There should be a restructuring of the work flow in Catia at LSH. All parts shouldcontain a body for every item, which would make it possible to apply different kinds ofmaterials on a part. How to do this should be taugth as early as possible, preferablywhen learnig Catia in the Catia introduction course.

All of the design changes are suggestions and the modified prototype is not complete,there is a lot more work to be done. Not all cables, cords, and pipes are covered inour model of the SEP, but those who are shows suggestions of how it should be done.The same applies to the floor, it should be used to hide cables and cords to avoid clutter.

8.2. Future Work 71

Table 8.1: The codecs that are installed on LSH’s computers and can be used forcompressing the movies

A suggestion for the parking break is to place it on the pedal stand instead of us-ing a hand break. It can be loosen with a hand control but it should be tightened withthe foot.

72 Chapter 8. Conclusions

Chapter 9

Acknowledgements

We have a number of persons that we would like to thank for helping us in differentways with this master thesis. In no particular order:

Fredrik Burholm

Our supervisor at LSH. Thank you. Your help has been invaluable.

Hakan Gulliksson

Our supervisor at Umea University. Thank you for your help with this report, it couldnot have been done without you.

Peder Nordin

Engineer at LSH. You have been a great help when we had questions about the SEP.

Fredrik Edin

IT support at LSH. Thank you for helping us finding the right codecs for the animations.Without you, no one at LSH would be able to see the movies.

Roger Elfving and Hakan Eriksson

Consultants at LSH. Thank you for testing IMA. It was valuable for the evaluation ofthe module.

Major Greger Lundkvist and Kapten Anders Moller

Major and Kapten at I19 in Boden. Thank you. Without your knowledge about militaryvehicles and the working environment in them, this master thesis and the redesign ofthe interior of SEP band2 would not have been possible to do.

People at LSH

Many persons have contributed to the result in our master thesis. You know who youare, thank you.

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74 Chapter 9. Acknowledgements

Family and Friends

Thank you for supporting and bearing with us.

References

[1] R. Barzel. Lighting controls for computer cinematography. Journal of GraphicsTools, 2(1-20), 1997.

[2] O.W. Bertelsen and S. Bodker. Activiy theory. In J.M. Carroll, editor, HCI Models,Theories, and Frameworks: Toward a Multidisciplinary Science. Morgan KaufmannPublishers, 2003.

[3] J. Birn. [Digital] Lighting and Rendering. New Readers Publishing, 2000.

[4] O. Demers. [Digital] Texturing and Painting. New Readers Publishing, 2002.

[5] B. Fleming. 3D Photorealism Toolkit. John Wiley and Sons, 1998.

[6] C.D. Green. Glitters: A review of psychological research on the aesthetics of thegolden section. Perception, 24(937-968), 1995.

[7] Berthold K.P. Horn. Robot Vision. The Massachusetts Institute of Technology,1986.

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[10] H. Mann and A.J. Ayer. Guidelines, principles, and theories. In B. Schneider-man and C. Plaisant, editors, Designing the User Interface- Strategies for EffectiveHuman-Computer Interaction. Pearson Education, 4 edition, 2004.

[11] R. Molich and J. Nielsen. Improving a human-computer dialogue. Communicationsof the ACM, 33(10), 1990.

[12] B.A. Nardi. Activity theory and human-computer interaction. In B.A. Nardi,editor, Context and Consciousness. The MIT Press, 1996.

[13] J. Nielsen. Traditional dialogue design applied to modern user interfaces. Commu-nications of the ACM, 33(3), 1990.

[14] J. Nielsen and R.L. Mack. Usability Inspection Methods. John Wiley and Sons,1994.

[15] J. Preece, H. Sharp, and Y. Rogers. Understanding users. In J. Preece, H. Sharp,and Y. Rogers, editors, Interaction Design. John Wiley and Sons, 2002.

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Appendix A

Eye Perception and theGestalt Laws

A.1 Eye Perception

The following paragraph referenced by [18, 20]

The eye processes a perceived object at different stages. First it processes informationinto features, then simple patterns, and finally more complex objects. The knowledge ofhow the eye perceives objects is useful when designing symbols and buttons that shouldstand out in a cluttered environment. This theory is called preattentive processingtheory. Preattentively distinct symbols stand out immediately from their surroundings.

A.2 The Gestalt Laws

The gestalt laws are some guidelines to follow when designing buttons and symbols, butalso to place objects correctly. The gestalt laws include following:

– Proximity Elements tend to be grouped together according to their nearness (seeFigure A.1, a)).

– Simplicity items will be organised into simple figures according to symmetry, reg-ularity, and smoothness.

– Similarity Items similar in some respect tend to be grouped together (see Fig-ure A.1, b)).

– Closure Items are grouped together if they tend to complete an entity (see Fig-ure A.1, c)).

– Common fate Objects that move together are perceptually grouped.

– Common region Objects close each other tend to be grouped together.

– Figure and ground People tend to organize perception by distinguishing betweena figure and a background (see Figure A.1, d)).

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78 Chapter A. Eye Perception and the Gestalt Laws

Figure A.1: Figures of proximity, similarity, closure, and figure and ground.

Appendix B

The Field Trip

B.1 Questions Asked on the Field Trip

– Is something missing in the vehicle?

– Is there something that could enhance the atmosphere in the vehicle while you arein the field?

– How long time can you spend in the vehicle without leaving it?

– How is the air condition handled?

– How do you sleep in the vehicle?

– Do you have personal items with you in the vehicle? If so, what kinds of items?

– Do you get travelsick from not seeing the road?

– How do you like the steering wheel?

– Does the vehicle hold everything necessary?

– Are there any physical limitations of the soldier?

– What would you like to change in the vehicle when it comes to interior, placementof objects, buttons, and etcetera?

– Where do you place the weapons while seated in the vehicle?

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80 Chapter B. The Field Trip

Appendix C

Images from the Redesign

Figure C.1: Instrument panel with three screens.

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82 Chapter C. Images from the Redesign

Figure C.2: Control buttons for the driver.

Figure C.3: Mechanical meaters.

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Figure C.4: Steering wheel.

Figure C.5: Close up on steering wheel.


Figure C.6: Plastic cover hiding pipes.

Figure C.7: Floor covering cables.

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Figure C.8: Floor covering cables.

Figure C.9: Floor in the back of the vehicle.


Figure C.10: Weapon holder

Figure C.11: Seat belt for the chairs in the back of the vehicle.

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Figure C.12: Four-point belt for the driver and the commander.

Figure C.13: A lamp, and an air controller for the soldier sitting in the right chair.


Figure C.14: Head rest for the driver and the commander.

Figure C.15: Head rest for the soldiers in the back of the vehicle.

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Figure C.16: Button for raising the driver’s chair.

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