Surface Modeling in Autocad

8/20/2019 Surface Modeling in Autocad

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Surface Modeling in AutoCAD® 2011

Guillermo Melantoni – Product Manager Autodesk

AC327-3P Learn about the new Surface Modeling feature in AutoCAD, and how it can be applied to theconsumer product and architectural market. Understand the potential for interoperability with Autodesk® Showcase®,Autodesk Inventor®, and Revit®

About the Speaker: Guillermo has worked for Autodesk since 2006, first as an Application Engineer based in Argentina, and currently asSenior Product Manager for User Interaction and Interoperability at Autodesk in San Francisco. In his previous role asProduct Manager for AutoCAD, he has been responsible for free-form design, surface modeling, parametric andoverall 3D enhancements in AutoCAD 2010 and 2011. Prior to this, Guillermo was part of the reseller channel inUruguay, as well as an architect and professor at two architecture schools. He has performed training andimplementations of AutoCAD, AutoCAD Architecture, Autodesk® Inventor®, AutoCAD Revit® Architecture, RevitStructure, and Autodesk 3ds Max®. Guillermo spends his free time playing video games or rocking hard with his

collection of bass guitars.


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1. Spline enhancements in AutoCAD 2011 ............................................................................. 3

2. Surface Modeling ...............................................................................................................14

a. Explicit Surfaces .............................................................................................................14

b. Surface Associativity ......................................................................................................14

c. Direct Manipulation .........................................................................................................15

3. Parametric Surfaces ..........................................................................................................29

a. Using expressions during surface modeling ...................................................................29

4. Explicit surfaces vs NURBS surfaces .................................................................................31a. Rationale ........................................................................................................................31

b. Editing NURBS ...............................................................................................................31

5. Workflows between surfaces, solids and meshes ..............................................................32

a. Surfaces into Solids ........................................................................................................32

b. Meshes into Surfaces .....................................................................................................33

6. Interoperability ...................................................................................................................39

a. With Autodesk Inventor ..................................................................................................39

b. With Autodesk Revit .......................................................................................................42

c. With Autodesk 3ds Max Design ......................................................................................54

d. With Autodesk Showcase ...............................................................................................42

e. With Autodesk Sketchbook Designer ..............................................................................54


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1. 2011

First of all, we need to talk about splines. These curves have been enhanced in AutoCAD

2011, and offer a quite powerful set of options that you need to understand in order to make the

best use of them. The old SPLINE command built a spline through Fit Points, also known as

Knots in spline lingo. Now, the construction of a spline through Fit Points is one of the three

options presented in the Curves panel in the Surface tab.

.

We will now check the new Spline CV option. This is the SPLINE command with a macro that

defines the selection of the Method. The two available Methods are Fit Points and Control

Vertices (CVs). Fit Points belong to the curve (when Tolerance is set to 0), while CVs are points

located outside of the spline. A change in a Fit Point is much more local than a change in a CV,

which can affect pretty much the whole spline.

Each method of creation has its own options. When defining the spline through CVs, we can

select the degree, for example. The degree in a Spline CV determines the distance to the

control vertices. As you can see in the image below, the highest the degree, the biggest the

distance to the CV, and thus, the smoothest the spline. A spline with degree 0 will basically look

like a polyline defined by a series of vertices. AutoCAD defaults to Degree 3, which is quite a

standard, but you can change this upon creation of the spline. You can eventually also edit this

by rebuilding the spline (explained later).

Spline Knot

Spline CV


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Depending on the reference geometry we have, one of the two methods will make more sense.If we know the location of specific points of the spline, then Fit Points will be better.

. In order to directly create a spline through Fit Points, we’ll use Spline Knot. The options inSpline Knot allow you to define the Knot parametrization. In order to explain this, we should getgeeky and check some maths. There are very good papers available around this topic.

.

However, we talked about three methods. The last one is the old SKETCH command, now

defined as Spline Freehand. This command has been updated, and can now produce not only

lines, but also polylines and splines. We can also determine the Tolerance and the Increment.

These options will make a lot of sense when using Spline Freehand. The bigger the Increment,

the less CVs the spline will have. If you want a lot of control over the curve and need more

control of smaller details in the geometry, a smaller Increment will help. Tolerance will

determine how close is the curve to the points that define it. Tolerance in 0 will force the curve

to be interpolated through these points.

Degree 4

Degree 0

Degree 2

Degree 3


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.

Let’s open the file 00 shaver.dwg in AutoCAD 2011. This is the model you should see upon

opening the file. If you change into 3D Modeling workspace, you will get a new Materials UI on

the right. Close it or minimize it for the time being.

The first thing we’ll do is to check the new options for Visual Styles within AutoCAD. The Visual

Styles panel moved from the Render tab into the View tab (they can also be found in the Home

tab).


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Depending on what you need to do, you may want to use Realistic visual style (the onepresented in the file by default). This is great when in need to show materials to a non-technical

audience or for communication in general.

However, being able to see edges or isolines may also be interesting. In surface modeling in

particular, visualization of the rows of UVs is very important, so we may want to target for a

visual style that already has a setting that allows the visualization of isolines.

In this particular case, we’ll use X-Ray, which not only shows the structure of the surfaces and

solids, but also has some level of transparency, that allows a better understanding of the object.

We are using Perspective View by default. Once we get into the creation of the curves, we may

want to be in Parallel View. We’ll do this by right clicking on the ViewCube, and selectingParallel View. The background color will also be regular, and identical to the one in 2d

wireframe. This way, we won’t see any changes when moving from an orthographic view into an

isometric view.


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In 3d modeling workspace, go to Home tab, View panel, and choose Right view.

We could have achieved something similar by clicking on the face named Right in the

ViewCube, with the exception that this does not make the UCS follow. Thus, if you chose Right

View through the last method, you won’t have the XY plane in the right place. This is only

relevant if you want to use the Spline Freehand option, which only allows a sketch on the XY

plane.

Now create a layer called Case_Bottom . Make it current, and turn the wire 1 layer on. You may

want to lock it, so you don’t mess up the points.

In the Surface tab, under the Curves panel, select Spline CV.

Make sure you have Node as an option in the OSnap Settings. You may notice, when you do

so, that there are also 3DOsnaps! But let’s talk about them later.


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Now just create the spline through the points in the wire 1 layer. Start in the last point at the

bottom and move up (in order to get the same results as the screen captures). You will notice

that only the first and last points belong to the curve. The rest are controlling the spline from

outside.

You can also use Show CV option in the Control Vertices panel in the Surface tab in order to

see the control vertices. You can either select the command and then click the spline, or do pick

first. Then, you’ll notice that you can see the control vertices at any time, and not just when the

spline is selected.

Click on a CV, and you’ll be able to move it on the plane or even in space. Try to play around

with the position of the CV for a while, and see how the spline reacts. For the exercise’s sake,

keep the point in its place once you try this for a while.


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If you hover over a CV in the spline, you’ll also notice that you get options for adding, removing

or refining vertices. The key idea to keep is that you may first approach the construction of the

spline with a basic sketch, and start refining it.

Try these options, and get comfortable with the whole workflow. Stretching a vertex is basically

moving the position of the CV. Add and Remove are quite self-explanatory. Refine Vertex

produces two CVs without altering the spline. This adds control to the curve for further editing.

Another interesting option is Rebuild (Control Vertices panel in the Surface tab). This

command enables you to change the degree and the amount of CVs in a spline. It also works

on surfaces. If you have a spline with many CVs (maybe you created it with Spline Freehand),

CVREBUILD will let you define the number of control points. Of course this may have an effect

on the shape of the surface, but this is controlled by the Preview, which shows the maximum


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distance between the original and rebuilt spline. This is called Maximum Deviation, and will helpyou decide if the change is acceptable or not.

Try the setting that is depicted in the image above, and click on Preview. You will see two

splines, and a representation of the Maximum Deviation. Of course, by removing a CV, we are

changing the spline quite drastically, but it may be exactly what you need.

If you hit Escape, the dialog box will appear again, and you will see the value of the Maximum

Deviation. If you had clicked Enter, you would have deleted the original spline and kept the

rebuilt one (since Delete original geometry was checked in the Rebuild Curve dialog).

Now let’s turn the wire 2 layer on, and do the same process with another Spline CV. You may

want to turn off wire 1 layer first.


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Click on all the points, and you should get a result like the one depicted below. Feel free to try astroke with Spline Freehand, and see if you can get comfortable with that command. If you

have a tablet and a stylus, this option may become a very good friend.

You may have noticed that if you click on the spline, there are a couple of new graphics

attached. The pink cross defines the starting point of the spline, while the other graphic will let

you move between CVs and Fit Points. Sometimes you will notice that creating a spline through

CVs is what you want, but at some point you want a specific Fit Point of the spline to be moved

to another location. That’s when you will like to have Fit Points displayed. The options in the

Right Click menu will also change depending on the type of control the spline currently has. And

yes, you don’t need to type SPLINEDIT anymore. It’s just a right click away.

Let’s complete the two remaining curves by turning wire 3 and wire 4 layers on. I would suggest

to do one curve at a time, and keep the rest of the points in the other layers off, in order to

decrease complexity.

Move into an isometric view, and use Spline CV to complete both curves. The end result should

look like this.


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We only have half of the shaver, which is good enough to get an idea of how to design the

curves that will define the whole case. Anyway, you may want to get the whole shaver and we

also need to get the curves for the other side of the case, so let’s use 3DMIRROR to get the

other half of the shaver and the two curves on the side. If you use the YZ plane as the symmetryaxis, just click on any point in the shaver’s section, and it will do the right thing.

And where’s 3DMIRROR? You can access it from the Home tab and Modify panel, or simply

type the command. Remember that if you start typing and use Tab, AutoCAD will suggest

commands, so if you just type 3dm and use Tab, you’ll get the 3DMIRROR command as a

second option (since they come in alphabetical order, and 3DMESH will come first).

After mirroring the geometry, you should have something like this.


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It’s time to start with surfaces. The first one will be a Network Surface. However, this kind of

surfaces needs curves on both directions. We’ll create the bottom of the case with them. This

means that we need to create some curves along the opposite direction to the bottom curve and

the two bottom curves at the sides. Since we know that the spline should have the three

endpoints as part of the curve, we will use Spline Knot.

Just select the Spline Knot option, and make two curves by clicking on the endpoints of the

previously mentioned splines. The result should be something like the image below.


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. Most of the interactions with surfaces and splines are done through the canvas, and not

involving dialog boxes, which tend to disrupt the process. You can see direct manipulation in the

multi-function grips on splines, on selection cycling, and in the controls for surfaces. All these

will be covered in the following example.

.

Even more important than learning the commands and different surface objects, is to know

when to apply which surface. Let me explain the whole process by showing you the final result

and identify the surface types.

The first surface we’ll do is a Network Surface using the three longitudinal curves and the two

curves we did between them. A Network Surface needs curves on both directions, and they

don’t even need to be intersecting. Of course, if they intersect and have coincident vertices,

then the surface will look exactly like we want. If not, there will be some interpolation done by

the computer, which we won’t exactly control.

Now we’ll complete the sides. We will use a Loft for this purpose, and we’ll consume the

remaining spline, and the edge of the surface we just created. Why? Because the selection of a

surface edge will allow us to control the continuity between the surfaces. In this case, we want a

perfect curvature between these two surfaces, so we’ll need G2 continuity. If we had selected


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both splines for the loft, we would not have had the chance to define continuity. That’s also thereason why we needed the Network Surface first.

The next operation is a loft, but in this case we can use the splines (the top spline and the top

splines from the sides). Why? The answer is simple. We just need to have coincident edges, but

not continuity, since this top surface will be a second part of the cover. We can also use the

surface edge with G0 continuity. If we do this, we’ll have associativity between the surfaces.


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The last operation will consist in closing the gaps on both ends. This will be done with Patch

Surface. Patch can operate with surface edges or curves, but in this case we’ll use surface

edges, even though we’ll force the solution to be a G0 (with no continuity in curvature or

tangency).


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Let’s start with the modeling.

The first surface we’ll do is the Network Surface. You need to select two sets of curves, which

have different directions. Once you finish selecting the first set of surfaces, you’ll click enter (or

whichever method you have for this), and then the second set of surfaces.

Let’s take a look at the Ribbon. The option for Surface Associativity is on. This means that if

you change the position of the elements that originated the surface, the Network Surface will

also change. The control lies within the original curves. This is a great differentiator with strict

NURBS modelers, which create a NURBS surface once you click OK. Please note that you can

also do this, by selecting NURBS Creation. In this case, all associativity is lost.

Let’s create our first surface using the Network command on the Create panel in the Surface

tab. Remember to select the first set of curves in one direction, and then the other set of curves,

after clicking Enter.


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If you have Properties open (if not, you can get it in many ways, but a simple one is through theQuick Access Toolbar), you will notice that if you select the surface, it is not only a Surface, but

it’s called a Network Surface. AutoCAD’s surfaces (if not created with the NURBS Creation

option) are explicit surfaces. It means that at any time, they keep the properties of the method

they were created with. We’ll see more value to this when we check the loft and the patch.

So we have the base of the case, but we now need the sides. We’ll use the Loft command.

LOFT has been around since 2007, but it has been enhanced, so let’s check some of these

enhancements. In our example, we are going to use a curve and a surface’s edge. In the past,loft was only possible with open or closed curves, and they had to be planar, at least the initial

and final profile.

In 2011, we can loft non planar profiles, and when one of the profiles is a surface’s edge, we

can control the continuity.

Select the LOFT command in the Create panel on the Surface tab, and then click on the top

spline on the side. Then, using Ctrl, click on the surface’s edge. As usual, Ctrl enables access to

subobject level, and in the case of a surface, to its edges. We need to select the edge, in order

to get access to the option for continuity. If we had selected the spline coincident with thesurface edge, we could have done the loft, but it would have worked as a G0, since the

command does not detect the adjacent surface when choosing the spline.

Once you finish selecting both profiles, you will get several options. Let’s focus on Continuity.

The options are G0, G1 and G2.

G0 (position) continuity means that there are no gaps, but there’s a sharp angle.

When you create G1 (tangent) continuity, it means that the surfaces have equal angles in their

tangency.


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When you create G2 (curvature) continuity, there’s not only equal tangency, but also equalradius in the curvature on both surfaces. These are the surfaces that don’t show any flaws when

lights are reflected on them. That’s why Zebra analysis is so important in these cases.

You will also notice that when you click on the loft, you’ll get a couple of new icons. If continuity

among surfaces is involved, then you will get at least three of them.

The one depicted below (the one to the right) will define the continuity. This is the one that will

only appear if at least one surface edge is selected as start or end profile. Please remember

that you can change this setting at any time.

The following icon provides different options for the loft operation:


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You can decide between a smooth fit and ruled loft (the latter will have G0 continuity between allinternal profiles).

You can also define if the loft is normal to any of its sections.

Draft Angle can also be triggered from here, although we’ll see that the last control is basically a

Direct Manipulation element for Draft Angle.

The last option is to close the surface or solid, which can also make a periodic surface.

The control for Draft Angle can also be accessed via Direct Manipulation. Once you click on the

triangle, you will get a handle that will control the magnitude of the draft angle, and reach very

interesting results.


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As you can see, AutoCAD 2011 has worked a lot around Direct Manipulation. This means thatyou can do pretty much any editing operation without having to go anywhere else than the

object itself.

However, you can access most of these options from the Properties palette too. Let’s take a

look at it.

First of all, AutoCAD recognizes the surface type as a loft.

This is an Explicit surface.

Under General, we will get the usual object properties,

such as Color, Layer. Please note that there’s a new

option called Transparency.

3D Visualization will let us access to the Material and to

control how the object casts and receives shadows.

Geometry is where we find the most interesting

information in terms of editing. Some options are grayed

out, since they can’t be changed from this palette.

Changing the number of cross sections would not make

any sense, for example. Other options, like Trimmed

surface, are not relevant until we don’t have such a

scenario (trimming elements).

Under Surface Normals, we can change the way the loft

behaves (Ruled, Smooth, etc). It’s the same control we

had on the object.

End Magnitude will control the Draft Angle. It may be

interesting to drag the control using Direct Manipulation, and then be able to fine tune it by

typing a more precise value in the Properties Palette.

The number of isolines does not affect the control of the surface, so just change it if you want to

have a different understanding in visual terms. Maybe a bigger amount of isolines along onedirection will help to make the surface more legible.

End Continuity is also a control we saw over the object. If we had used continuity with two

surfaces, we would have had Start and End Continuity (and Start and End Magnitude).

We can also see that the loft is not closed (under Misc)

Surface Associativity enables us to control if the surface will keep associativity, and we can

also ask AutoCAD to show associativity. If we change this value into Yes, you will see how the

spline and surface edge highlight (image below, to the right)


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We have already solved the bottom and the sides. Let’s see what to do with the top. Why the

top first? Because we have all the data to create the next surface. And we need this new

surface in order to close the gaps at both ends. That’s the rationale.

We will do another loft. This time, using three splines. Why do we choose to use the splines and

not the other surface’s edge? Simply because we want them to be adjacent, but they don’t need

to share continuity. As it was mentioned before, you can still use surface edges and apply G0

continuity.

First, let’s make a new layer called Case_Top , and change its color, so we can easily recognize

both parts of the object.

We’ll use the LOFT command again, this time with the two top splines on the side, and the top

spline we first did. Please note that we need to select the cross sections in order.

When you select the first spline, you will notice a new icon over the cursor. It tells you that there

is more than one element of geometry there, and it’s called Selection Cycling. You can also

toggle it on and off from the Status Bar (the last icon to the right).

Selection Cycling will display any geometry that coexists in the point that you clicked, unless the

option is too obvious. For example, when selecting subobject in a Box, and you click over an

edge, AutoCAD will assume you want the edge, and not the two faces that converge into that

edge.


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In our case, if we want to select the spline, AutoCAD will also find the previous loft. So that’sexactly what it will show in an adjacent box. You can hover over the options, and you’ll see them

highlighting on screen.

A couple of tips on Selection Cycling.

First of all, if the first choice that is displayed is the right one for you, you can keep selecting the

other elements, since AutoCAD will take the default one as the one selected. If it is not, just

move your mouse over the options, and click on the one you like.

If you are in a drawing that’s too busy, you may want to turn it off. Just do it from the Status Bar.

The results from this loft should look like the following image.


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You may want to go back to visual styles, and select Realistic, which will tell you if there are anycollisions with the shaver. You won’t find any problems with the geometry, of course.

But let’s create some problems, and take a look at surface editing. While the surface is a loft,

and it’s associative, we still have control of the splines that were used as cross sections.

Select the top spline and you’ll get the Selection Cycling box, since both the spline and the loft

share the same space. Depending on the angle of your perspective, you’ll probably also get the

network surface done for the bottom, and the shaver (solid).

Once you have the spline selected, hover the mouse over one of the CVs, and you will see that

the Gizmo will move to that location. Now move the CV along the axis normal to the surface

(depending on how you did the exercise, this may vary). Make sure you go down, towards the


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Let’s use the option called Patch. A Patch is a surface type that will create a surface that closesa gap. The boundaries can be either curves or surface edges. Please note that you can’t mix

curves and surface edges. When you use surface edges, the patch will ask for the type of

continuity. You can also constrain the patch with additional geometry. For example, you want

the patch to go through a specific point, or an ellipse. In this case, we’re going to make it simple,

but feel free to try some of these options.

Change the current layer to Case_Bottom , and then use the Patch option (SURFPATCH

command), which is on the Surface tab, in the Create panel. Select all the surface edges at the

bottom (in no particular order), and you should get something like this.

Before the command ends, you are prompted for three different options. You can control the

continuity (as we already learnt with the loft), you can define a Bulge magnitude, and add a

Constraint.


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Select Continuity, and play a little with G1 and G2. You will notice that the surface changesaccording to the continuity you select. For the exercise’s sake, keep it in 0.

If you have G1 or G2, the Bulge will help you define the shape of the patch. Try to change it

from the Properties palette, and put it in 1 (remember to change continuity too). This is what it

looks like with G2 and Bulge in 1.

Go back to the Patch in G0, and do the same to the other end. It looks like we have a nice

conceptual design for a shaver’s case!


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.

. Most of the surfaces prompt for an Expression as one of the options upon creation. If you are

using the 3D Modeling workspace, you won’t have access to the Parametric tab, which is solely

available on the 2D drafting and annotation workspace. That said, by customizing the CUI, you

can easily add the Parametric tab to the 3D Modeling workspace, by simply dragging it from the

list of Ribbon tabs into the available tabs in your workspace.

Let’s say we add two User Parameters called Angle1 and Angle2. We want to control the angle

of revolution of two Revolved surfaces. They are both related. One of them is half of the other,

and revolves in the reverse direction.


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As an example, let’s blend both surfaces with G2. Take a look at the result. After changing theangle (second image), we can see how the three surfaces update and reflect that change. Now

that’s productivity.


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.

. So if explicit surfaces are so convenient, why would you need NURBS? Simply because

NURBS can allow for even more flexibility in cases where the method of creation is not relevant,

and probably too restrictive. For example, if you need to create a bump in a specific part of a

surface, then it will be very hard to edit curves in order to get the right result.

By converting an explicit surface into NURBS, you lose associativity, but get the power to edit

the hull (a collection of control vertices), and to use the CV edit bar.

. Convert to NURBS is located in the Control Vertices tab. Once you convert to NURBS, you can

use the Show CV option to display the hull. If it’s too dense, or not enough dense, you can also

use Rebuild. In this case, instead of amount of CVs, it will prompt for amount of Us and Vs.

Now you can simply use the Gizmo on one or several control vertices (if you want to select

several, you need to use Shift)


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When rebuilding surfaces, always make sure that there are no gaps with adjacent surfaces,

since AutoCAD is not tracking associativity any more.

. ,

. There are a couple of ways to create solids from surfaces.

The first of them is by applying thickness. This can be done from two commands: THICKEN (in

Solid tab), and by OFFSETSRF (in Surface tab).

Make sure that the thickness is not big enough as to create self-intersections. In those cases,

the command won’t work.

In this example, by applying Offset Surface (OFFSETSRF) to this surface, we can get a solid

very easily. Once it’s a solid, it’s going to be hard to edit, so make sure that the shape is quite

defined if you convert to solid. Surfaces are much more flexible, since they keep associativity.


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When you select Offset, the surface will indicate the direction of the offset. By right clicking weget access to the contextual menu, where you’ll select Solid, and will define a thickness. Done.

SCULPT is a very powerful command introduced in AutoCAD 2011. Now you can create a solid

from any set of watertight entities. Could be all surfaces, solids and surfaces. As long as there

are no gaps, AutoCAD will consider the volume watertight, and will be able to perform the

operation.

In this example, you can try Sculpt after making sure that all the sides are correctly closed. A

simple selection of all the elements is the only thing you need.

. When AutoCAD introduced subD surfaces in AutoCAD 2010, some people had doubts about

the accuracy of the method. They were right, since a subD mesh is basically generating a curve

by interpolation of planar faces. It was a method introduced by companies like Pixar to generate

smooth surfaces without such demanding times of render that a perfect curve would produce.

Meshes are also extremely flexible, and very intuitive to use. That said, when our designs need

to go to production, it’s a very different story than a design whose only purpose is a render.

AutoCAD has defined some workflows between meshes and surfaces. Let’s suppose we have

tweaked a torus into this shape using SubDs. Getting to this shape by creating profiles would


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have been quite a complex task. Especially during conceptual design, where the end form maynot be that clear.

Now we’ll convert the mesh into a smooth optimized surface. This is done from the Convert

Mesh in the Mesh tab. Selecting smooth optimized will make AutoCAD stitch faces with G2

continuity. This enables you to have the least amount of NURBS patches.

We already have a surface. We now need to convert it into NURBS surfaces. The current entityis a body that stitches many surfaces together. By converting to NURBS, we’ll get the individual

NURBS surfaces. You need to do this if you need to be more precise when editing some

specific part of the surface.


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The following image shows a NURBS surface isolated from the rest. Depending on the type ofediting done in the mesh, you can get a fairly clean set of surfaces. In this case, the surface has

been converted into 4 NURBS surfaces. Not bad.

By clicking on Show CV and selecting the surface, we can see the hull. We can also Rebuild the

surface if we need more control on the U and V direction. We could also eventually change the

degree.

The hull is easily editable by dragging one or more control vertices with the Gizmo. This is

another example of direct manipulation. The Gizmo will not only allow movement, but can also

accept keyboard input of any distance.


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If the hull does not have enough control vertices we can rebuild it. However, we may not need

too much density everywhere, but only in a specific part. That’s the reason for the addition of the

command CVADD (you can find it in the Control Vertices tab, as Add). You can define the

direction, and choose to add control vertices or knots. This has the same rationale than what we

talked in the section about splines. In the image below you can see how we can track the

position of the new row of CVs.

This seems enough powerful, but let’s go one more level deeper. Maybe we don’t want to define

more rows of CVs. Then the CV Edit bar is what you need. The CV Edit bar (the command is

called 3DEDITBAR) will track a specific point in the surface.


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As soon as we define the position of the point, we’ll click and see the Gizmo appear in this

location. This Gizmo is pretty much the same as the one we already know. It does have somemore features. One of them is really important if you want to move normal to the surface. You

can find it under Align Gizmo With. If you select Object, then the Z in the Gizmo will be directed

perpendicular to the surface. In the case of this particular example, finding that direction would

have been quite difficult.

Once we have the Gizmo where we want it, we can then drag it in the usual way.


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As a final step, you can use Thicken on the surface, in order to get a solid. The part is closer to

being manufactured. You can also create documentation with the already existent Section

Plane.


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. AutoCAD’s surfaces are a quite flexible and powerful environment, which may be a very good

front end for conceptual design. That said, if you want to continue the design into production,

Inventor is probably the right tool. They both use the same modeling kernel, so the information

flows very smoothly from one application into another. The only caveat is that what gets into

Inventor is the brep, so for now, the associativity is lost. If you change the design in AutoCAD,

you need to reimport the model into Inventor.

Once we save the solids or surfaces in AutoCAD, we’ll export an SAT file, which we’ll open in

Inventor. I recommend setting the sysvar ACISOUTVER to 0 before exporting.

In this case, we imported the bottom of the case as a solid (using the same example from the

previous parts).

Now we’ll do a Shell in Inventor. We could have also done this in AutoCAD, but Inventor offers

an environment highly specialized for manufacturing, with many workflows that will make your

life much easier. Since AutoCAD stays in generic shapes, it is more flexible. But at this stage of

the design, we may require the power of discipline specific tools.

Inventor will also ask for faces to remove, and we’ll select the top face.


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The results of the shell should look like the image below.

Now it’s time for the ribs. This is a great example of a process that’s really faster in Inventor.

Creating these ribs in AutoCAD would have taken several steps. In Inventor, we will just

define two lines in auxiliary workplanes, and use the command Rib, which will solve the

unions for us. At any time, we can also move the workplanes, or edit the thickness of the rib,

and the whole model will update.

Finally, by copying the body of the shaver into the part and using the Sculpt command, we

can get rid of the parts of the rib we don’t need.


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At the end of this process, this will be the assembly. Inventor would be much more suitable ifyou want to continue developing the part for fabrication, since it also has a powerful set of

tools for plastics, and of course, for making the mold that you may need in order to make

mass production of these parts.


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. Showcase is a great tool for Design Validation and overall communication for your idea. You

can import the dwg done in AutoCAD or the iam done in Inventor into Showcase, and create

stunning presentations for your product.

Once you import the model into the scene, you can change the materials using Showcase’s

Material Browser (the shortcut is M). It is organized into Categories, just like the one in

AutoCAD, so you’ll notice that any work in materials will have an almost nonexistent learning

curve.

You can also define the Scene (the shortcut is S). The lighting coming from the scene impacts

in the model, since Showcase uses Image Based Lighting. You can select any of the images

offered in Showcase, or import a new scene. You will need an HDRI image for this.


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You can also control the scene’s scale, and the position of the model with respect to the scene’sfloor.

Once you have the model finished, you can generate Shots and make small animations like the

ones that can be done in AutoCAD with ShowMotion.


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.

When working in a conceptual design in AutoCAD, we may want to continue our work in Revit.

Although the complete model could be done in AutoCAD, Revit offers discipline specific tools

that will enhance your productivity, and allow you to integrate your AutoCAD conceptual design

into a Building Information Modeling process.

We will now create a solid from the set of surfaces. Revit will be able to create slices from a

solid, in order to create floors. We’ll use a design that started as a couple of meshes for the

towers, which were then converted into faceted solids. The base of the building was built with

surfaces.

We’ll set DELOBJ sysvar to 0 for a moment, so the surfaces are not deleted after the

SURFSCULPT command creates the solid.

After invoking SURFSCULPT, or clicking on the Sculpt icon in the Edit panel, you just need to

select all the surfaces, and a solid will be created. If you also select the meshes in the same

operation, AutoCAD will create a single solid. In this particular case, I’d suggest to do

conversion to faceted solids when working with the meshes (the two towers), and sculpting the

surfaces for the rest of the building.


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It is quite likely that when in Revit, you will want to slice the towers and the base according todifferent levels. This task is easier if you make individual exports into Revit.

The canopy will not be sculpted into a solid, since it’s open geometry. You can take that part

separately too. It will work perfectly well in Revit, but it won’t be possible to slice it. Not a

problem. We will just create Wall by face, so the surface has enough information for that.

Create wblocks with every part of the building, being careful about sharing the same origin. My

suggestion is to use 0,0,0.

If you click on any part of the building, you will see that Selection Cycling shows you both the

surfaces and the solid you just created. Select the solid, and right click. You will find new

options that were introduced as an Advantage Pack for Subscription during AutoCAD 2010.Select the option called Isolate, and you will be able to isolate the solid. In our case, it’s the only

thing we had in the Solid layer, so it would have been easy to just isolate the layer. But imagine

when you have multiple elements in a layer. That would have taken more time. With the new

timesaving tools, this is really fast.

The following images show the last steps. We isolated the solid, and created a block with

WBLOCK, since we want it to reside outside of this file.


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The purpose of this part of the example is not to deliver a detailed process within Revit, but to

show the overall workflow. I’m based on the assumption that you have some familiarity with

Revit. If that is not the case, you may also want to refer to Revit material available on the web.

The first thing we’ll do in Revit, after we open a new project, is to create some In-place masses

where we’ll insert the different parts of the conceptual design.

We need to click on the Massing & Site tab, and choose Create In-Place Mass.

Revit will prompt for a name. Add a name for the mass. Make sure it’s easy to identify,

especially if you are going to insert many other elements.

Once the mass is named, click on the Insert tab, and in the Link panel, you will see an option

called Link CAD. We are going to link the dwg file into Revit.

Browse the files we just created in AutoCAD, and insert one at a time.


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Make sure that Positioning is set to Origin to Origin and not the default setting of Center to

Center. Since we created a wblock in AutoCAD, the file will already be purged from anything

else. If you are not clear about the possible existence of hidden elements in the dwg, you can

select Visible in the Layers option.

The file in AutoCAD was done in meters (if you used the files in the tutorial). Revit canautodetect the units, but if you want to make sure everything is ok, just select meter in Import

units.


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Once the process of linking and importing the dwg ends, you should see something like theimage below. If you have made a zoom or don’t see anything, make sure you type ZA (for Zoom

All).

Finally, click on Finish Mass.

Now repeat the process for the towers and the canopy. The canopy will display a warning that

no Floors can be made with the geometry you imported. We are perfectly fine with that.

The next step will be to create some levels, so let’s select an Elevation from the Project

Browser. Select East, and you will see the model just like the image below.

Now we need to create an array of levels. First set the distance between levels into something

that makes sense to the scale of this space. I put 7 meters between floors, so the space

between slabs is not perceived as so horizontal.


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The result should be something like the image below.

Now that we sliced the mass, we need to convert those slices into floors. In the Home tab, you

need to select Floor by Face from the Floor drop down (Build panel). Once you have selected

Floor by Face, simply select the slices, and create the floors.


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You can go back to Massing & Site, and disable Show Mass, in order to understand what weare doing.

After completing the floors, we can continue with the rest of the components. In this case, I

added Curtain Systems, a Roof and a Wall.

After linking the rest of the masses, the end result will look like the last image. This is actually a

good starting point where the architect can start defining the space, materials, and later he can

start creating 2D views of the project.

AutoCAD was of great help, as we saw, for the initial part of the design, providing a very flexible

and probably familiar environment for modeling with solids, meshes and surfaces. Depending

on the office, the conceptual design and the development will be done by different people, with

different backgrounds and definitely different skills. Having conceptual design in AutoCAD as

another alternative of a front end solution for design is just adding more power to your repertoireof potential solutions.


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.

Interoperability between AutoCAD and 3ds Max Design is probably much better known than

with the rest of the applications, so this explanation will be brief. If you need more information,

you can refer to the class that myself and Marion Landry are also presenting at Autodesk

University 2010 (DV430-1 AEC Workflow for Autodesk ® Design Suite).

The most important element to consider is how to import the data from AutoCAD. It all depends

on where you will decide to apply materials. AutoCAD and 3ds Max Design now share a

common and very powerful material library called Autodesk Material Library. This means that

any material applied in AutoCAD will be displayed by 3ds Max Design if you import the file asdwg.

The best way to import the file is through File Link Manager in 3ds Max Design. You can find it

in the App Frame (the M on the top right), under References. Please refer to the class

mentioned above for details on best practices around settings. If the import is done defining the

right settings (on tessellation, grouping, etc), then the process in 3ds Max will be much faster.

.

Autodesk Sketchbook Designer is a new product that is offered within the Autodesk Design

Suites. It is a combination of two products. Sketchbook Designer for AutoCAD is a plug in that

appears as a tab within AutoCAD, and there is a standalone version called Sketchbook

Designer. You will need both.

For more information, please refer to another of my classes (AC422-2: Get Your

Presentations and Design to the Next Level with Autodesk® Alias® Sketch for

AutoCAD® ). The product changed its branding during the year, so Alias Sketch was the old

name.

Sketchbook Designer will allow you to do very powerful sketching, which can be both raster and

vector. Vector sketching is only allowed in the standalone application. You can then export the

curves into AutoCAD, and use them for surface modeling.

This is probably the use of Sketchbook Designer that is more related to this class. You can also

use the product for compositing images (as you may do in image editing software). The

differentiator is that you can underlay 2D or 3D geometry from the model space in AutoCAD into

paper space, and sketch over it. It’s a great tool for communicating an idea.


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Let’s see an example extracted from the class DV430-1 mentioned before.

In this example, we need to sketch the basic shapes for building a pavilion in a specific location.

From the Insert tab in AutoCAD, you should attach an image and scale in order to have its real

size. Scaling with reference is very useful for this.

In order to use Sketchbook Designer for AutoCAD, you need to be in Paper Space. Go to Paper

Space and create a viewport if one has not been created automatically. Sketchbook Designer

for AutoCAD uses a different concept, called Canvas.

You will now create a Canvas over the Viewport, so the information in the Viewport is converted

into what Sketchbook Designer can use.


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Once you define the Canvas using the viewport vertices as snapping points, Sketchbook

Designer will prompt for some data about the page. The relevant part for us now is to select

Create Paint Underlay ON. This will “bake” the viewport into the canvas as a raster image.

If you use software for editing images, you will be familiar with the Canvas Browser. The layers

are stacked according to draw order. The underlay layer can’t be used for sketching, since it’s

locked. That’s why Sketchbook Designer creates a Paint layer on top of the latter, in order to

have a canvas where to work.


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The next step is to create a Vector sketch. This can only be done in Sketchbook Designerstandalone. There is a one click workflow enabled with Sketchbook Designer that automatically

opens the standalone version and locks the current drawing in AutoCAD. The option for this is

the tab called Environments.

In Sketchbook Designer you will now create a Vector layer by clicking on the Layer menu. You

need a vector layer in order to generate editable curves. If you do the same strokes from a Paintlayer, you’ll simply obtain a bitmap.

There is also another access point for creating and editing layers inside the current layer’s box,

as you can see in the image below.

You can now start sketching. In this case, I suggest to create a paint layer and paint some

background in order to work with less distraction from the aerial photograph. It is clear than in

other situations, you definitely need the data in the photograph, so in those cases simply create

the sketch with the vector layers.

If you do prefer to have background for your sketch, there are a couple of controls you may like

to understand. The first is the size of the brush. While you use the slider on the left, you’ll have

feedback on the screen, with a stroke that will show you what you are configuring. This stroke

disappears as soon as you finish editing the size. You’ll also get the same one for transparency.


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The other control to know is the color wheel. It is quite simple to understand. The background

color in the wheel represents the current color.

While you create the strokes, you’ll notice a graphic next to your vectors. You can control the

spline with it, by simply dragging it. Try it in order to get a feeling of its power. You can also click

on it, and get different options, that include a straight line, a perfect arc, etc. You can see in the

picture below how the curve becomes a straight line by simply clicking on that control


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You may also want to edit those curves by tweaking the control points. There are a couple of

options in Sketchbook Designer that allow you to select either complete segments, or segments

within the curve, or the overhanging parts after an intersection. All of these features are

absolutely necessary if you want good control of the geometry. Remember that you can start

modeling based on this geometry.

You can now delete the background you created. Simply use the radial menu and select Delete.

You are now ready for going back to AutoCAD.


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Now you will export the curves and also do a one click workflow back to AutoCAD. The curveswill be exported without the rest of the raster content, as a dwg file. When you do the one click

workflow and go back into AutoCAD, you will see that all that you did here (bitmap or raster)

was baked into raster images. You will see vector layers in AutoCAD, but won’t contain real

curves. Your curves are coming in the separate dwg file. The two images below explain both

methods. From File > Export, you will export the curves into dwg, and you will also click on the

last button on the Sketchbook toolbar in order to go back into AutoCAD and unlock your

drawing.

The next step will involve merging both the curves and the aerial photo. Once you do the one

click workflow and go back to AutoCAD, you will see the sketch on top of the aerial photo.

Open the file exported from Sketchbook Designer, and you will see the curves.

Now copy the curves and paste them into the file that contains the aerial photo (in Paper Space)


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Next step will involve moving the geometry and scaling it so it fits the image. Use scale with

reference as a more accurate method.

That said, you may remember you do have the photograph in Model Space. So why did we do

this in Paper Space? Simply because you have the reference to the geometry here. Now copy

this geometry and paste it back in model space. You may need to draw a reference around theimage, in order to be able to snap in model space.

Last thing to do is rescale the curves with your reference so it fits the real photo. Why did we do

all this? Simply because Model Space and Paper Space in AutoCAD are two very different

environments.

Now you have the geometry in its right place, so you are ready to start modeling. And you have

used your own sketch converted into curves. How cool is that?


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• AutoCAD’s surface modeling empowers you with significant flexibility to build precision

surfaces.

• This flexibility is critical in an exploration process, which makes this feature very powerful

for conceptual design.

• The main aspects that you need to remember about surfaces in AutoCAD are:

o Explicit surfaces: surfaces remember their method of creation, and can be edited

using those properties

o Surface associativity: changes in the geometry that drove the creation of the

surfaces will replicate all over the parts of the model that are related to them

o Direct manipulation: mostly all operations are done in canvas, reducing the need

for dialog boxes

• Surfaces are also parametric, which means that you can add User Parameters,

constraints (to the 2D geometry that generates the surfaces), and create expressions.

• There are very interesting workflows between the different topologies within AutoCAD

(solids, surfaces and meshes)

• We have also covered interoperability workflows that relate AutoCAD with most of the

main products from Autodesk’s portfolio.

• AutoCAD as a front end for conceptual design can be understood as part of both Digital

Prototyping and Building Information Modeling processes.

Surface Modeling in Autocad

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