Advance Surface Modelling

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AdvancedSurface Modeling

Learning ObjectivesA fter completing this chapter, you will be able to:

Understand and work with different types of surface models.

Create procedura l surfaces.

Create N URBS surfaces.

Create network surfaces.

Create surface models from existing su rfaces.

Blend a nd patch sur faces.

Offset, fillet, extend, and trim surfaces. Convert existing models to NURBS surfaces.

Edit N URBS surface control vert ices.

Convert 2D objects to surfaces.

Thicken a surface into a solid.

Sculpt watertight su rfaces into solids.

Overview

This chapter describes advanced surface modeling techniques and workflows

used in AutoCAD. Surface modeling provides the ability to create a more freeform

shape w ith tools that solid mod eling cannot provide. You have been introduced to

basic surface modeling techniques in previous chapters. As you have learned , one way

to create surface models is to extrude, revolve, sweep, or loft profiles. This chapter

builds on those techniques. In this chapter, you will develop an understanding of

surface modeling techniques that can stand alone in the design process or work in

combination w ith other modeling techniques.

As discussed in previous chapters, a solid modelis created with a closed and

bounded profile and has mass and volume properties. A mesh consists of vertices,

edges, and faces that define the 3D mesh shape. A mesh does not have ma ss or volum e.

Asurface modelcan be though t of as a thin-walled object with no Z dep th. A surface

model does not have mass or volume.

O ervi w

ChapterChapter

This sample chapter is for review purposes only. Copyright The Goodheart-Willcox Co., Inc. All rights reserved.


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302 AutoCAD and Its ApplicationsAdvanced

2. Create the cell phone case shown. Create the case as an extru ded surface. Create a

patch surface for the top su rface. Then, use the a rcs to trim the sides.

A. Draw the base profile in the top view using the dimensions given.

B. Draw the arcs in the top view. The arcs should extend pa st the perimeter of

the cell phone case. Draw t he first arc on the r ight side of the profile and then

mirror it to the other side. Move the arcs along the Z axis so they are located

.75 units above the bottom of the cell phone case.

C. Extrud e the base profile to a height of .5 un its.D. Create the top of the cell phone case by creating a patch su rface with C2 conti-

nuity a nd a bu lge magn itude of .125.

E. Trim the sides by projecting the arcs and selecting areas to trim.

F. Save the dr awin g as P11_02.

Cutting objectsA B

Chapter 11 Advanced Surface Modeling

3. Create the hair dryer hand le shown. Create the base profile using a spline and a

straight line segment. Use the p rofile to create a planar surface. Then, extrude th e

planar surface and fillet the bottom en d. Finally, convert the model to a NURBS

surface and ed it the top surface.

A. Draw a spline and a line using the profile shown. Use the CVoption of the SPLINE

command to create a CV spline. Dimensions are n ot important. Create the general

shape by picking points to define the control vertices as indicated. Draw a line to

form t he straight segment at the end of the handle. Then, use the JOIN commandto join the line to the spline. The resulting object should be a single, closed spline.

B. Create a plan ar surface from the profile.

C. Extrud e the planar su rface to a height of .85 units.

D. Use the SURFFILLET command to fillet the bottom end of the handle. Use a

radius of .375 un its. Set the t rimm ing mod e toYes.

E. Using the CONVTONURBS comma nd, convert the m odel to a NURBS surface.

Edit the control vertices of the top surface to create a different shape.

F. Save the dr awin g as P11_03.

Line

A

B

Points picked forCV spline

Resulting spline


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4. Create the computer spea ker using surface modeling comm and s. Use associative

surfaces and edit the h eight from 4.5 units to 6 un its, as shown. Save the draw ing

as P11_04.

A

B

Chapter 11 Advanced Surface Modeling

5. Create the kitchen chair show n. In earlier chapters, you created th is model as a

solid m odel. In th is problem, use surface modeling comm and s to create the model.

Use the d rawings show n to create the seat, seatback, legs, and crossbars.

A. Create the top of the seat using the p rofile shown. Use the edge profile to create

the cur ved, receding edge extending to t he bottom of the seat. The bottom of

the seat is 1below t he top.

B. Create the profile geometry for the seatback. Loft the circular cross sections to

create the supp orts. Loft the square and circular cross sections to create the bow.C. Create the framework for lofting the legs and crossbars as shown on th e next

page. The crossbars are at the midpoints of the legs. Position the lines for the

double crossbar about 4.5 apart. The legs transition from 1.00 at the ends to

1.25 at the m idpoints. The crossbars tran sition from .75 at the end s to 1.00

at a p osition 2from each end.

D. Save the drawing as P11_05.

Seat Profile Edge Profile

Seatback Profiles Completed Seatback


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Profiles for Legs and Crossbars

Completed Model

Advance Surface Modelling

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