Chapter 23
Exploring 3D Mesh and Surface Modeling
AutoCAD has always offered tools that allowed users to construct fairly complex 3D models. With the solid-modeling tools, you can even model some very organic forms. But there are some types of forms that require a type of modeling known as mesh modeling. Mesh modeling enables you to create smooth, curved volumes by manipulating faces that make up an object’s surface.
With mesh modeling, you can quickly create curved shapes that are difficult or even impossible to create by other means. AutoCAD also offers the ability to convert a mesh model into a 3D solid so that you can perform Boolean operations.
AutoCAD for Mac introduces a set of 3D surface modeling tools that extend its ability to produce and edit curved, organic forms. In this chapter, you’ll get a chance to explore many of the current features of mesh modeling through a series of exercises, and you’ll be introduced to the new surface modeling tools. You’ll also learn how you can convert a mesh or 3D surface into a solid. You’ll start by creating a simple shape as an introduction, and then you’ll move on to a more complex form.
In this chapter you’ll learn to do the following:
- Create a simple 3D mesh
- Edit faces and edges
- Create complex meshes
- Convert meshes to solids
- Understand 3D surfaces
- Edit 3D surfaces
As an introduction to the mesh modeling features in AutoCAD, you’ll draw a simple box and then smooth the box. This first exercise will show you some of the basic mesh modeling tools and what types of control you can exert on a model. Follow these steps:
1. Create a new file using the acad3D.dwt or acadiso3D.dwt template. Choose File New from the menu bar, or press F-N.
2. At the Select Template dialog box, select the acad3D.dwt template (metric users can select acadiso3D.dwt) and then click Open.
3. From the Tool Sets button, select Modeling.
4. Choose the Shaded With Edges visual style from the Visual Styles menu on the Viewport Controls. This will give you a close approximation of the appearance of meshes you’ll see in the figures shown in this book.
Creating a Mesh Primitive
Meshes are similar to solids in that they start from what is called a primitive. You may recall that 3D solid primitives are predetermined shapes from which you can form more complex shapes. The mesh primitives are very similar to the 3D solid primitives you learned about in Chapter 19, “Creating 3D Drawings,” and Chapter 22, “Editing and Visualizing 3D Solids.” You can see the different mesh primitives that are available by choosing Draw 3D Modeling Meshes Primitives from the menu bar or by typing MESH↵.
In the next exercise, you’ll use the mesh box primitive to start building your seat cushion:
1. Type MESH↵ B↵.
2. At the Specify first corner or [Center]: prompt, enter 0,0↵ to start the mesh at the drawing origin.
3. You’ll want a mesh that is 21 units in the X axis by 32 units in the Y axis, so at the Specify other corner or [Cube/Length]: prompt, enter 21,32↵ (metric users can type 533.4,812.8↵).
4. At the Specify height or [2Point]: prompt, place your cursor anywhere above the base of the mesh and enter 4↵ for a 4-inch height (metric users can enter 101.6). You now have a basic shape for your mesh (see Figure 23-1).
Figure 23-1:The mesh box primitive
You’ve just created a mesh box, but you have several other mesh primitives at your disposal. When you typed the Mesh command, you saw the cylinder, cone, sphere, pyramid, wedge, and torus primitive options. When creating your model, consider which of these primitives will best suit your needs.
Understanding the Parts of a Mesh
Before you go any further, you’ll want to understand the structure of a mesh. Notice that each side is divided into nine panels, or faces as they are called in AutoCAD. You can edit these faces to change the shape and contour of your mesh. You can also control the number of faces that a mesh will display, which will be covered in the section “Editing Faces and Edges” later in this chapter.
Figure 23-2 shows the names of the different parts of a simple mesh: the vertex, the edge, and the face. These three parts are called subobjects of the mesh, and you can move their position in the mesh to modify a mesh’s shape.
Figure 23-2:The subobjects of a mesh
To help you select different subobjects on a mesh, the Subobject Selection Filter submenu (located on the right-click shortcut menu) offers the Filter flyout, which shows the No Filter tool by default. You’ll use this flyout in many of the exercises in this chapter.
Smoothing a Mesh
One of the main features of a mesh is its ability to become a smooth, curved object. Right now your cushion has sharp edges, but you can round the corners using the Smooth tools.
Try modifying the mesh to smooth its corners:
1. Click the rectangular mesh to select it.
2. Type MESHSMOOTHMORE↵ (or choose Modify Mesh Editing Smooth More from the menu bar). The edges of the mesh become faceted and smoother in appearance.
3. Repeat the MESHSMOOTHMORE command. The mesh becomes smoother still (see Figure 23-3).
Figure 23-3:The mesh after applying the Smooth More tool twice
4. Now type MESHSMOOTHLESS↵, select the object, and press ↵ (or choose Modify Mesh Editing Smooth Less from the menu bar). The mesh becomes less smooth.
5. Press Esc to clear the selection.
Don’t Forget the Right-Click Menu
The Smooth More and Smooth Less options are also available on the right-click shortcut menu.
As you can see from this exercise, you can smooth a mesh using the Smooth More tool. The more times you apply it to a mesh, the smoother your mesh becomes. The number of faces of the mesh determines how Smooth More affects the mesh. The fewer the faces, the broader the application of smoothness.
When you apply the Smooth More tool to a mesh, the faces of the mesh become faceted. This simulates the smooth appearance. If you look closely at a mesh that has only one or two levels of smoothing applied, you can see the facets.
The shape you created earlier demonstrates one of the main features of meshes. In this section, you’ll create a model of a surfboard to see how you can push and pull the subobjects of a mesh to create a form.
You’ll start with the same form, a box shape, but this time you’ll modify some of the parameters that define the box’s structure. You can control the number of faces that a mesh primitive will have before it is created. The following exercise introduces you to the tools and methods used to edit meshes.
Know the ViewCube
Throughout the following exercise, you’ll make heavy use of the ViewCube. Make sure you are familiar with how it works. If you need a refresher, see Chapter 19.
Start by creating a new drawing and setting up the parameters for the mesh.
1. Choose File New from the menu bar (or press F-N), select acad3D.dwt, and then click Open. Metric users can select the acadiso3D.dwt file.
2. Choose the Shaded With Edges visual style from the Visual Styles menu on the Viewport Controls.
3. Type DIVMESHBOXWIDTH↵ 4↵. This sets the mesh division for the box width to four faces instead of the default three.
4. Type DIVMESHBOXLENGTH↵ 4↵. This sets the mesh division for the box mesh length to four faces instead of the default three.
5. Finally, type DIVMESHBOXHEIGHT↵ 1↵. This sets the mesh division for the box mesh height to one face instead of the default three.
The parameters you change alter the number of faces on mesh primitives that you create, including the box primitive in the next exercise. You’ll see the results in the next set of steps:
1. Type MESH↵ B↵ to create a primitive mesh box.
2. At the Specify first corner or [Center]: prompt, type 0,0↵ to start the corner at the origin of the drawing.
3. At the Specify other corner or [Cube/Length]: prompt, enter 50,30↵ to create a 50˝--30˝ base for the box. Metric users can enter 1270,762↵.
4. At the Specify height or [2Point] prompt, point the cursor in the positive Z direction and then enter 3.5↵ for a 3.5 units thickness. Metric users enter 88.9↵.
5. Center the box in your view.
6. Click the mesh box to select it. On the Properties Inspector palette, click the Smoothness drop-down list in the Geometry group. Select Level 4. Your mesh box is now smoothed again as it was originally. Your model should look similar to Figure 23-4.
Figure 23-4:The mesh box
What Does the Smooth Mesh Tool Do?
The Smooth Mesh option on the menu bar (Draw 3D Modeling Meshes Smooth Mesh) is not intended to work on meshes. Instead, it converts 3D objects other than meshes into mesh objects. You can convert a solid into a mesh, for example, using this tool. 3D surfaces can also be converted, and it even works on region objects that are technically not 3D objects.
You might be tempted to convert a mesh to a solid, edit it, and then turn it back into a mesh. Although this can be done, we don’t recommend it. You’ll find that your model becomes too unwieldy to work with.
Stretching Faces
You now have the basis for the surfboard, though it might seem like an odd shape for a surfboard. Next you’ll start to form the surfboard by manipulating the faces and edges of the mesh. Start by pulling two sides of the mesh to give it a shape more like a surfboard:
1. Use the ViewCube and Pan tools to adjust your view so it looks similar to Figure 23-5. This view will allow you to easily select and “pull” some of the faces that will become the front and back of the surfboard.
2. Click on the box and then right-click. From the shortcut menu, select Subobject Selection Filter Edge.
3. Notice the mesh lines. This will help you see where to place the selection window in the next step.
4. Hold down 
and then click and drag a crossing selection window over the middle faces at the front edge of the box, as shown in Figure 23-5. The faces are highlighted, and you see the XYZ gizmo.
5. Place your cursor on the red X axis of the gizmo.
Figure 23-5:Hold down the key and place a crossing selection window as shown here.
6. When the red axis extension line appears, click and drag the gizmo downward in the positive X direction. The mesh begins to elongate.
7. When your mesh looks similar to Figure 23-6, click your mouse button.
8. Press Esc twice to remove the faces from the current selection and remove the current selection filter.
Figure 23-6:Click and drag the gizmo when you see the red axis extension.
The portion of the mesh you “pull” out will become the front. Next, do the same for the back of the surfboard:
1. Use the Pan tool to adjust your view so it looks similar to Figure 23-7. This view will allow you to easily select and “pull” some of the faces that will become the back of the surfboard.
2. Click on the box mesh to expose its mesh lines again.
Figure 23-7:Hold down and place a crossing selection window as shown here.
3. Hold down and then place a crossing selection window over the middle faces at the back edge of the box as shown in Figure 23-7. The faces are highlighted, and you see the XYZ gizmo.
4. Place your cursor on the red X axis of the gizmo, and when the red axis extension line appears, click and drag the gizmo upward in the negative X direction.
5. When your mesh looks similar to Figure 23-8, click your mouse button.
6. Press Esc to remove the faces from the current selection.
7. Click the Home tool on upper-left side of the ViewCube to get a better view of your mesh so far (see Figure 23-9).
Figure 23-8:Adjust the mesh to look similar to this one.
Figure 23-9:The mesh so far
Moving an Edge
The surfboard needs a sharper point at the front. Instead of moving the faces as you’ve already done, you can move an edge to give the front a more pointed shape. The next set of steps will show you how to do this:
1. Using the ViewCube, adjust your view so you have a close-up of the front tip of the surfboard, as shown in Figure 23-10.
2. Click on the mesh and then right-click. Choose Subobject Selection Filter Edge from the shortcut menu.
3. Hover over the front edge until you see the edge line, and then click the edge, as shown in Figure 23-10. The XYZ gizmo appears.
4. Hover over the X axis of the gizmo, and when the red extension line appears, click and drag the X axis downward along the positive X direction.
5. When it looks similar to Figure 23-11, click the mouse button.
Figure 23-10:Click the front-center edge shown here.
Figure 23-11:Pull the front edge so that the mesh looks similar to this image.
Next, give the front of the mesh a slight curve by adjusting the Z axis of the front edge:
1. Hover over the Z axis of the gizmo, and when the blue axis extension line appears, click and drag the Z axis downward in the negative Z direction.
2. When it looks similar to Figure 23-12, click the mouse button.
Figure 23-12:Move the front edge downward in the Z axis.
3. Press the Esc key to clear your edge selection.
4. Click the Home tool in the ViewCube to return to the home view.
I asked you to adjust the edge downward because you’ll want to have a bottom view of your surfboard. This will enable you to add fins to the board without having to flip the mesh over.
Fine-Tune the Mesh
You might notice that the surfboard has a slight trough down the middle after you move the front edge downward. You can remove that trough and add some additional curvature to the board by moving the two edges on the side of the mesh toward the front.
You can click edges with the Edge subobject filter selected. Once you have these edges selected, use the blue Z axis on the gizmo to move them down to eliminate the trough.
Adding More Faces
The surfboard is still missing some fins. You could model some fins as separate meshes and then later join them to the surfboard. You can also use the MESHREFINE command to add more edges and then use those edges as the basis for your fins. The following exercise will show how this is done:
1. Adjust your view so it looks similar to Figure 23-13.
2. Click on the mesh and then right-click and select Face from the Subobject Selection Filter.
3. Click the faces shown in Figure 23-13.
Figure 23-13:Select the faces to refine.
4. Right-click and select Refine Mesh from the shortcut menu. The selected faces will be subdivided into smaller faces and edges, as shown in Figure 23-14. (You can also type MESHREFINE↵.)
Figure 23-14:The refined faces
Understanding How Refine Mesh Works
You have some control over the number of faces that Refine Mesh creates through the level of smoothness applied to a mesh. If you reduce the smoothness of a mesh, the Refine Mesh tool will produce fewer faces. If you increase the smoothness, Refine Mesh will produce more faces—four more per facet, to be precise.
To understand how this works, you have to take a closer look at how the Smooth More tool works. Each time you apply the Smooth More tool to a mesh, every face of the mesh is divided into four facets. These facets aren’t actually faces, but they divide a face in such a way as to simulate a rounded surface. The Refine Mesh tool further divides each of these facets into four faces. You can see this division clearly if you apply Refine Mesh to a face in a mesh that has only one level of smoothness applied.
The next step in creating the fins is to edit some of the newly created edges:
1. Zoom into the surfboard so your view looks similar to Figure 23-15.
2. Click on the mesh and then right-click and select Edge from the Subobject Selection Filter flyout.
3. Click the edges shown in Figure 23-15.
Figure 23-15:Select the edges for the fins.
4. Hover over the Z axis on the gizmo so that the axis extension appears, and then click and drag the Z axis upward in the positive Z direction. If you run out of room at the top of the window, move the Z axis as far as you can with one click and drag, and then repeat the Z axis move.
5. Adjust the edges so they look similar to those in Figure 23-16, and then click the mouse button.
6. Adjust the X axis of the gizmo toward the back of the surfboard so the fins look similar to how they look in Figure 23-17.
Figure 23-16:Adjust the edges to create the fins.
Figure 23-17:Adjust the fins toward the back of the surfboard.
7. Press the Esc key to clear your selection of mesh edges.
Rotating an Edge
The fins still aren’t quite the right shape. They are a bit too broad at the base. The next exercise shows you how to rotate an edge to further adjust the shape of the fins:
1. With the Edge subobject filter still selected, click the back edge of the fins as shown in Figure 23-18.
Figure 23-18:Click and drag the green circle on the Rotate gizmo.
2. Right-click over the gizmo, and choose Rotate (see Figure 23-19).
Figure 23-19:Select the Rotate gizmo tool.
3. Hover over the green circle of the Rotate gizmo in the location shown in Figure 23-19 until you see the green axis extension, and then click and drag the mouse to rotate the edge. Adjust the rotation of the edge so that the fins look similar to those in Figure 23-20, and then release the mouse button.
Figure 23-20:The finished surfboard
4. Press the Esc key to clear your selection.
5. Use the Home tool on the ViewCube to get an overall view of the surfboard (see Figure 23-20).
In this exercise, you switched from the Move gizmo to the Rotate gizmo. You can also use the Scale gizmo to scale a face or edge.
This may not be the most accurate rendition of a surfboard (our apologies if you are a surfer), but the general shape of the surfboard has given you a chance to explore many of the features of the Mesh toolset.
Changing the Gizmo on-the-Fly
In addition to the right-click menu, you can change the current gizmo using the Gizmo drop-down list on the expanded status bar. You can also set the orientation of the gizmo through the Gizmo shortcut menu, which will allow you to move subobjects in directions other than perpendicular to the face or edge. You can orient the gizmo to the WCS, the current UCS, or a face on a mesh through the Align Gizmo With option on the shortcut menu (refer back to Figure 23-19).
Adding a Crease
The Add Crease tool can help you fine-tune your mesh shapes. It does exactly what it says. It can introduce a crease in your otherwise smooth mesh shape. The Add Crease tool does this in two ways: It can flatten a face or remove the smoothing around an edge.
In the following exercises, you’ll use the surfboard one more time to experiment with the Add Crease tool. First you’ll see how you can add a sharp point to the surfboard:
1. Adjust your view of the surfboard so you can see the front point, as shown in Figure 23-21. Turn off the grid so you can see the shape clearly.
Figure 23-21:Set up your view. Select the front edge of the surfboard.
2. Type CREASE↵ (or choose Modify Mesh Editing Crease from the menu bar). At the Select mesh subobjects to crease: prompt, select a face from the front as shown in Figure 23-21 and press Enter.
3. At the Specify crease value [Always]<Always>: press Enter.
You can see from this exercise that the front edge of the surfboard is now quite sharp since it no longer has any smoothness, as shown in Figure 23-22.
Figure 23-22:The surfboard after applying Add Crease tool
The surfboard is grossly deformed, but you can see how the side faces have now become flat and the edges of the face form a crease. You could use the Add Crease tool to sharpen the edge of the fins. This would also have the effect of making the fins thinner.
Splitting and Extruding a Mesh Face
There are two more tools that can be a great aid in editing your meshes: Split Face and Extrude Face. The Split Face tool will split a face into two faces. The Extrude Face tool behaves like the Extrude Face tool you have seen for 3D solids. Both of these tools are a bit tricky to use, so they bear a closer look.
To use the Split Face tool, you first select a mesh face, then select two points, one on each side of the face. The following exercise shows how it works:
1. Open the SplitMesh.dwg sample file from the Chapter 23 folder, which can be obtained at www.sybex.com/go/masteringautocadmac. This file contains a simple mesh box that has been smoothed.
2. Type MESHSPLIT↵ (or choose Modify Mesh Editing Split Face from the menu bar).
3. Click the face shown in Figure 23-23.
4. Move the cursor to the left edge of the face until you see a knife icon appear next to the cursor.
5. Click roughly in the middle of the edge.
Figure 23-23:Select this face.
6. Move the cursor along the right edge of the face. You’ll see some temporary lines giving you a preview of the location of the split (see Figure 23-24).
Figure 23-24:Selecting the points for the split
7. Move the cursor roughly in the middle of the right edge. The face changes temporarily to show you how it will look when it is divided into two faces.
8. Click the mouse button. The shape of the mesh changes to accommodate the new face.
As you can see, Split Face is not a precision tool, but if you don’t like the location of the split, you can move the newly created edge using one of the gizmos.
Next, let’s look at the Extrude Face tool. At first, you might think that the Extrude Face tool is redundant since you can use the Move gizmo to move a face in a direction away from the mesh, as you saw in an earlier exercise. Using the Extrude Face tool is different from moving a face because it isolates the movement to the selected face as much as possible. To see how this works, try the following:
1. Type MESHEXTRUDE↵ (or choose Modify Mesh Editing Extrude Face from the menu bar) and then click the face as indicated in Figure 23-25. Press ↵.
Figure 23-25:Select this face.
2. Click and drag the Z axis in the positive direction. When the mesh looks similar to Figure 23-26, click to finish the move. The smoothness of the side is maintained as you pull the face.
Figure 23-26:The moved and extruded face
You can see from this example that the Extrude Face tool confines the deformation of the mesh to only the face you select. Note that you can select multiple faces for the extrusion.
Using Split Mesh Face and Add Crease Together
In a “usability study” conducted by Autodesk, the product designers gave an example of how to add a crease to the top surface of a computer mouse model. In that example, the Add Crease tool and the Split Face tool were used together. First, a new edge was created using the Split Face tool, and then the Add Crease tool was applied to the newly created edge to form the crease. Using these two tools together in this way, you can add a crease just about anywhere on a mesh.
So far, you’ve been working with mesh volumes, but the Mesh submenu on the Draw menu offers four tools that let you create a variety of complex meshes. These are the revolved, edge, ruled, and tabulated surfaces. They are the latest incarnation of some of the earliest 3D tools offered by AutoCAD, and they work exactly like the old features they replace. But just like the mesh volumes you’ve been working with, the mesh surfaces can be quickly smoothed, and their subobjects can be edited using the gizmos you learned about in this and earlier chapters. The following sections give a little more detail about these tools and how they are used.
The following instructions are for your reference only and you are not required to do them as exercises. But if you like, you can try them out on the SurfaceMeshSamples.dwg file provided with the sample drawings for this chapter located on the book’s companion website.
Revolved Mesh
To create a revolved mesh, you need a profile to revolve and a line that acts as an axis of revolution (see Figure 23-27). The profile can be any object, but a polyline or spline is usually used.
Figure 23-27:The Revolved Surface tool
To create a revolved mesh, follow these steps:
1. Type REVSURF↵.
2. At the Select objects to revolve: prompt, select the first object, as shown in Figure 23-27. This is known as the Profile. Then press ↵ and select the axis object.
3. At the Specify object that defines the axis or revolution: prompt, press ↵ and select the second object, as shown in Figure 23-27. This is known as the axis object.
4. At the Specify start angle <0>: prompt, enter the angle of rotation for the surface, or just press ↵ to accept the default angle of 360°. As you might infer from the prompt, you can create a revolved surface that is not completely closed.
Getting Smoother Surfaces
The mesh surfaces will appear faceted when you first create them. Typically, the revolved, ruled, and tabulated surfaces will have 6 faces. The edge surface will have an array of 36 faces. You can increase the number of faces that are generated by these tools by changing the Surftab1 and Surftab2 settings. Surftab1 will increase the faces generated by the revolved, ruled, and tabulated surface tools. Surftab1 and Surftab2 can be used to increase the faces of an edge surface.
To use the Surftab settings, type SURFTAB1↵ or SURFTAB2↵ and enter a numeric value. The value you enter will be the number of faces generated by these surface mesh tools. Don’t get carried away; an increase in the number of faces will also increase the size of your file. Besides, you can always use the Smooth More tool to smooth out the appearance of these surface objects.
Edge Mesh
In Chapter 22 you learned how to draw a butterfly chair that has the shape of a draped fabric seat. Before the newer 3D modeling tools were introduced, the Edge Surface tool (see Figure 23-28) was used in that butterfly chair example. This tool is a bit trickier to use only because the objects defining the surface must be selected in sequential order. In other words, you can’t randomly select the objects.
Figure 23-28:Results of using the Edge Surface tool
Here’s how it works:
1. Type EDGESURF↵.
2. Select the four objects that are the edges of the surface you want to create. Make sure you select the objects in clockwise or counterclockwise order. Don’t select them “crosswise.”
Ruled Mesh
The Ruled Mesh tool creates a surface mesh from two 2D objects such as lines, arc, polylines, or splines. This is perhaps the simplest mesh tool to use since you only have to click two objects to form a mesh (Figure 23-29). But like Edge Mesh, it has a tricky side. You’ll want to click the same side of each object unless you want the surface to twist as shown in Figure 23-30.
To create a ruled mesh, take the following steps:
1. Type RULESURF↵.
2. Click two objects that are not on the same XY plane. The mesh is created between the objects.
Figure 23-29:The finished ruled surface
Figure 23-30:Where you click on objects affects the outcome.
Tabulated Mesh
The Tabulated Mesh tool is like an extrude tool for surfaces (see Figure 23-31). Chapter 19, “Creating 3D Drawings,” showed you how you can use the Extrude tool to create a 3D solid from a closed polygon. The Extrude tool will also work on open polygons, lines, and arcs, but it will extrude the object in only a perpendicular direction. The Tabulated Surface tool lets you “extrude” an object in a direction you control with a line. The line can point in any direction in space.
Figure 23-31:The Tabulated Surface
Here’s how to use it:
1. Type TABSURF↵.
2. Select the object that defines the profile of your mesh.
3. Click the object that defines the direction for the surface.
As with the other surface mesh tools, the point at which you select objects will affect the way the object is generated. For the tabulated mesh, the direction of the mesh depends on where you click the line that defines the surface direction.
Converting Meshes to Solids
I mentioned earlier that you can convert a mesh to a solid. In doing so, you can take advantage of the many solid-editing tools available in AutoCAD. The Boolean tools can be especially useful in editing meshes that have been turned into solids.
The conversion process is fairly simple using the tools in the right-click shortcut menu when you pick a mesh or type CONVTOSOLID↵ and then select the mesh or meshes you want to convert. Press ↵ to complete the process. The Convert To Surface tool (CONVTOSURFACE↵) works in much the same way, but it creates a surface object instead of a solid.
So far in this book, you’ve worked with 3D solids and meshes. A third type of 3D object, called a surface, completes AutoCAD’s set of 3D modeling tools to make AutoCAD for Mac a complete 3D modeling application in its own right.
When you click the Tool Sets button on the Tool Sets palette and choose Modeling, you’ll see the tools you’ll need to work with surface modeling. You can also see more of them via Draw 3D Modeling Surfaces and Modify Surface Editing on the menu bar.
You can see quite a few tools that we haven’t covered so far. These surface creation tools work in the same way the mesh tools work. In fact, they are the essentially the same tools. They just use a different command option to create a surface instead of a solid. The big difference is that to create a solid, you need to start with a closed polyline. With the surface version of the Loft, Sweep, Extrude, and Revolve tools, you can start with an open spline, polyline, or other object. And even if you do use a closed object, such as a circle or closed polyline, you will still get a 3D surface instead of a solid (see Figure 23-32).
Figure 23-32:A circle extruded using the solid Extrude and the surface Extrude
Two additional surface creation tools are the Surface Network and Planar Surface tools. Here’s a brief description of each:
Surface Network tool The Surface Network tool (Figure 23-33) lets you create a surface from several curves.
Figure 23-33:Creating a surface with the Surface Network tool
Planar Surface tool With the Planar Surface tool, you can create a flat surface either by selecting two points to indicate a rectangular surface or by selecting a closed 2D object to create a flat surface with an irregular boundary, as shown in Figure 23-34.
Figure 23-34:Creating a planar surface
Surface objects have a unique set of editing tools that allow you to create fairly detailed models. Some tools, like Surface Fillet and Surface Trim (see Figure 23-35), offer the same function as their 2D drawing counterparts. The following list includes a description of each tool. They are discussed in more detail later in this section.
Surface Extrude The Surface Extrude tool will allow you to take a 2D object and turn it into a 3D object.
Surface Trim The Surface Trim tool lets you trim one or several surfaces to other surfaces. You can also type SURFTRIM.
Surface Untrim Surface Untrim does exactly what it says. It reverses a trim operation. You can also type SURFUNTRIM.
Surface Fillet With the Surface Fillet tool, you can join one surface to another with an intermediate rounded surface (see Figure 23-35).
Offset Surface Offset, like the Surface Trim tool, mimics its 2D counterpart. It will create a new surface that is parallel to the original. When you start the Surface Offset tool from the Surfaces – Create tool group and select a surface, you’ll see arrows indicating the direction of the offset. You can type F↵ to flip the direction of the offset. Enter a distance for the offset and press ↵ to create the offset surface (see Figure 23-36). You can also type SURFOFFSET.
Figure 23-35:Using the Surface Fillet and Surface Trim tools
Figure 23-36:Using the Surface Offset tool
Blend Surface Blend will connect two surfaces with an intermediate surface. You can also type SURFBLEND.
Patch Surface Patch will close an open surface like the end of a tube. Surface Patch also lets you control whether the closing “patch” is flat or curved, as shown in Figure 23-37. You can also type SURFPATCH.
There are two other surface editing tools to make mention of. They are Surface Extend and Surface Sculpt. Although I won’t go into great detail, they are shown for your reference. The following includes a description of each tool:
Surface Extend The Surface Extend tool simply enables you to extend the edge of a surface beyond its current location. Unlike its 2D equivalent, it does not extend a surface to another surface object, though you could extend beyond a surface and then use the Surface Trim tool. You can also type SURFEXTEND.
Surface Sculpt The Surface Sculpt tool is like a super trim. You can align several surfaces to completely enclose a volume (left image in Figure 23-38), then use the Surface Sculpt tool to trim all of the surfaces at once into a completely closed 3D shape (right image in Figure 23-38). By default, the new object is a solid.
Figure 23-37:The Surface Patch tool can create a flat or rounded patch over a open surface.
Figure 23-38:The Surface Sculpt tool creates a container-like shape from several surfaces.
Using Extrude, Surface Trim, Surface Untrim, and Fillet
Now that you have an overview of the basic surface modeling tools, try the following set of exercises to see firsthand how they work.
Using the Extrude Tool
Start with the Extrude tool on two basic shapes:
1. Open the Surfaces1.dwg file, which can be obtained at www.sybex.com/go/masteringautocadmac. Note that the visual style shown on the Viewport Controls is set to 2D Wireframe.
2. Choose Extrude from the Surfaces – Create tool group on the Tool Sets palette.
3. At the Select objects to extrude or [MOde]: prompt, type MO↵ SU↵. This will create an extruded surface.
3. Click the circle in the drawing, and then press ↵. A surface appears and its length changes as you move the cursor.
4. Adjust the surface height to 5 units so it looks similar to Figure 23-39.
5. Click Extrude again and extrude the arc horizontally 5 units so it looks similar to the extrusion in Figure 23-39.
Figure 23-39:Extrude the circle and arc (left image) 5 units to look like the image on the right.
Using the Surface Trim and Surface Untrim Tools
The Surface Trim tool is similar to the 2D Trim tool except there is the additional step at the beginning where you have to select the object you intend to trim. Let’s try it:
1. Click Surface Trim from the Surfaces – Edit tool group on the Tool Sets palette.
2. Click both the cylinder and the extruded arc surface, and then press ↵. This first step selects the objects to trim.
3. Click both objects again and then press ↵. This time you’re selecting the objects to trim to. You want to trim the top of the cylinder to the arc and the arc to the cylinder.
4. Finally, click the cylinder near the top edge to indicate what part you want to trim. Also click the extruded arc surface anywhere outside of the cylinder. Your surfaces should look like the right image in Figure 23-40.
Figure 23-40:Trimming the surfaces
The Surface Untrim tool will revert your trimmed object back to its original shape. To do this, follow these steps:
1. Click the Surface Untrim tool from the Surfaces – Edit tool group on the Tool Sets palette.
2. Click the top edge of the cylinder and press ↵. The arc is back to its original extruded shape.
Go ahead and perform the Surface Trim operation on the arc again. You’ll need this shape for the next exercise.
Notice that the original arc you used to extrude the arc surface is still there. You’ll use that a little later in this chapter.
Using the Surface Fillet Tool
Now try out the Surface Fillet tool:
1. Click the Surface Fillet tool from the Surfaces – Edit tool group on the Tool Sets palette.
2. Click the top surface as it is shown inside the cylinder and then click the cylinder. The two surfaces are filleted, as shown in Figure 23-41.
Figure 23-41:Using the Surface Fillet tool
3. The prompt Press Enter to accept the fillet surface or [Radius/Trim surface]: appears. Type R↵ to enter a different radius.
4. Type 0.5↵. The radius changes. You still have the opportunity to change the radius again.
5. Type R↵ and then type 0.2↵. The radius changes again.
6. Press ↵ to finish the fillet.
Using Surface Offset, Surface Blend, and Surface Patch
As mentioned earlier, a few of the tools on the Tool Sets palette are a bit like editing tools. Surface Offset, Surface Blend, and Surface Patch create new surfaces that use existing surfaces as their basis. Surface Offset creates a new surface that is parallel to an existing one and is similar to the 2D Offset command. Surface Blend is a bit like the Surface Fillet tool in that it will join two surfaces with an intermediate surface. Surface Patch will create a surface that closes an open-ended surface.
To get a better idea of how these three tools work, try the following set of exercises.
Using the Surface Offset Tool
Start by creating a parallel copy of an existing surface using the Surface Offset tool:
1. Open the Patch1.dwg sample file which can be obtained from the Chapter 23 sample folder on the book’s companion website.
2. Click the Surface Offset tool from the Surfaces – Create tool group on Tool Sets palette.
3. Click the surface in the drawing and then press ↵. You see a set of arrows appear as shown in the left image of Figure 23-42.
Figure 23-42:Using the Surface Offset tool
4. Type F↵. The arrows now point in the opposite direction.
5. Type F↵ again to return the arrows to their previous direction, facing outward.
6. Enter 0.5↵ for the offset distance. The offset surface appears around the original surface as shown in the right image of Figure 23-42.
The arrows play an important role in helping you visualize the result of your offset, so instead of picking a direction, you adjust the direction of the arrows.
Using the Surface Blend Tool
Now try the Surface Blend tool:
1. Use the Move command to move the outer surface vertically in the Z axis roughly 5 units. Remember that you can hold down the 
key to restrain the cursor to the Z axis. If you see the Surface Associativity message, click Continue. You’ll learn more about associativity later in this chapter.
2. Adjust your view so you can see both surfaces, and then click the Surface Blend tool from the Surfaces – Create tool group on the Tool Sets palette.
3. Select the eight edges along the top of the lower surface as shown in Figure 23-43. When you’re sure you’ve selected all of the edges, press ↵.
4. Select the eight edges along the bottom of the upper surface as shown in Figure 23-43. When you’re sure you’ve selected all of the edges, press ↵. A new, preview surface appears that joins the upper and lower surfaces.
Figure 23-43:Selecting the edges for the Surface Blend tool
In steps 3 and 4, if you cannot pick more than one edge at a time, make sure you have the system variable PICKADD set to 1.
5. You might notice a couple of grip arrowheads that appear along the top and bottom edge of the new blend surface. Click one of them and a menu appears offering three options: Position, Tangent, and Curvature (Figure 23-44).
6. Click Curvature on one of the grips.
7. Click Curvature on the other grip to blend the surface.
The Surface Blend tool offers a number of options that control the shape of the blend surface. You saw three options available from the grip arrowhead. The options are available even after you have placed the surface. You can click on the surface to expose the grip arrowheads.
In addition, the Surface Blend tool offers two command options: CONtinuity and Bulge magnitude. Table 23-1 describes these features and their functions.
Figure 23-44:Using the grip arrowhead to adjust the blend surface
Using the Surface Patch Tool
Now let’s take a look at the Surface Patch tool. The Surface Patch tool lets you close the end of a surface with another surface. You can add a flat or curved surface as you’ll see in the next exercise.
Try adding a patch surface to the top of the upper surface in the Patch1.dwg model:
1. Pan your view so you can clearly see the top of the surface model as shown in the left image in Figure 23-45.
2. Click the Surface Patch tool from the Surfaces – Create tool group on the Tool Sets palette.
3. Select the eight edges of the surface as shown in Figure 23-45.
4. Press ↵ when you are sure you’ve selected all of the edges. The patch surface appears.
5. Click the grip arrowhead that appears along the edge of the patch and select Tangent. The surface is now curved.
Figure 23-45:Adding the patch surface to the end of the model
6. Press ↵ to finish the patch surface.
7. To get a better view of the surface, select the Shaded With Edges option from the Visual Styles menu in the Viewport Controls.
You may have noticed that the grip arrowhead options in step 5 were similar to the grip options you saw for the Surface Blend tool. The Surface Patch tool offers an additional command option called CONStrain geometry. Table 23-1 describes these options.
Table 23-1: The Surface Blend and Surface Patch options
| Option | Function |
| (G0) Position | Causes the surface to connect without any blending curvature. |
| (G1) Tangent | Causes the surface to blend with direction. |
| (G2) Curvature | Causes the surface to blend with direction and similar curvature or rate of change in surface direction. |
| CONtinuity | Controls how smoothly the surfaces flow into each other. |
| Bulge magnitude | Allows you to adjust the amount of bulge or curvature in the blend surface. Values can be between 0 and 1. |
| CONStrain geometry (Surfpatch command) | Offers additional guide curves to control the patch surface. |
Understanding Associativity
Surface Associativity is a feature that is on by default, and its function is similar to the Associative feature of hatches (see Chapter 7, “Mastering Viewing Tools, Hatches, and External References,” for more on hatches). You may recall that when you create a 2D hatch pattern with the hatch Associative feature turned on, the hatch’s shape will conform to any changes made to the boundary used to enclose the hatch pattern.
Surface Associativity in surface modeling works in a similar way, only instead of a hatch pattern conforming to changes in a boundary, the surface conforms to changes in the shapes that are used to create them. For example, if you were to make changes to the arc that you used to extrude the arc surface, the arc surface and the trimmed cylinder would also follow the changes.
Using Associativity to Edit a Surface Model
Rather than try to explain any further, let’s try it out so you can see firsthand how associativity works:
1. Return to the Surfaces1.dwg file and click the arc to expose its grips.
2. Click the square grip at the arc’s left endpoint and drag it downward along the Z axis. When it is roughly in the position shown in Figure 23-46, click again to fix the grip’s location. The shape of the surface model changes to conform to the new shape of the arc.
Figure 23-46:Adjusting the shape of the arc
3. Zoom into the top of the surface model so you have a view similar to Figure 23-47.
Figure 23-47:Adjusting the fillet radius
4. Click the filleted portion of the surface. An arrowhead grip appears.
5. Click the arrowhead grip. Another arrowhead grip appears.
6. Click this arrowhead grip and slowly drag it toward the center of the cylinder. Notice that the radius of the fillet changes as you move the grip.
7. Click to fix the fillet radius to its new size.
8. Press the Esc key to clear your selection.
Using Arrowhead Grips to Edit a Surface
You’ve just seen the Surface Associativity feature in action. You can also change the shape of the circle used to extrude the cylinder to modify the surface model’s diameter. There are additional hidden grips that allow you to adjust the shape of the surfaces directly. For example, you can modify the taper of the cylinder using an arrowhead grip that you can turn on through the Properties Inspector palette, as shown in these steps:
1. Click the cylindrical part of the surface model.
2. In the Properties Inspector palette, scroll down to the bottom until you get to the Surface Associativity category. Make sure All is selected in the Properties Inspector palette before you can see the Surface Associativity category.
3. Click the check box next to Show Associativity. You now see the circle at the base of the cylinder in a bold outline.
4. At the top of the cylinder, click and drag the right-pointing arrowhead grip to the right. As you do this, you see the dynamic display showing you an angle (see the left image in Figure 23-48).
5. Position the arrowhead grip so that the angle shows 6°, and then click to fix the grip in place. The cylinder is now tapered and the top surface conforms to the new shape, as shown in the right image in Figure 23-48.
Figure 23-48:Changing the taper of the cylinder
Surface Associativity can be very useful, but in order to take full advantage of this feature, you will want to plan your model construction carefully. In addition, Surface Associativity can limit some editing and creation functions. For example, the Surface Fillet tool may not work on a complex surface model with associativity turned on but will when the associativity is turned off for the objects involved.
Turning Off or Removing Associativity
You can turn off or remove associativity for an object through the Properties Inspector palette. Select the object, and then in the Properties Inspector palette, scroll down to the Surface Associativity category (see Figure 23-49). This category offers two options: Maintain Associativity and Show Associativity. The Maintain Associativity option offers Yes, Remove, and None options.
Figure 23-49:The Surface Associativity panel in the Properties Inspector palette
You can select Remove to remove associativity altogether or select None to limit the associativity to the set of objects currently associated with the surface model. Once you change this setting, you can’t return to a previous setting except with an Undo.
Constraints, Surfaces, and Associativity
In Chapter 16, “Making “Smart” Drawings with Parametric Tools,” you learned that you can add constraints to objects to control their behavior. With Surface Associativity turned on, you can extrude constrained objects and the resulting surface will also follow the constraints of the source 2D objects. But remember that if you use constraints with 3D surfaces in this way, you need to carefully plan the way you build your model to make efficient use of constraints.
Editing with Control Vertices
So far you’ve been creating procedural surfaces, which are surfaces that allow you to take advantage of associativity. AutoCAD also allows you to create NURBS surfaces. You may recall that splines are also NURBS, so you might think of a NURBS surface as a kind of 3D surface spline. Splines allow you to move, add, or subtract control vertices, or CVs, and you can control the way the CVs “pull” on the curve of the spline. Likewise, NURBS surfaces allow you to add or remove CVs and adjust the direction and force of the CVs.
There are two ways to create a NURBS surface. You can turn on the NURBS Creation option by typing SURFACEMODELINGMODE↵ 1↵ and then go about creating your 3D surfaces. Any 3D surface you create with this option turned on will be a NURBS surface.
Converting a Surface to a NURBS Surface
You can convert an existing surface to a NURBS surface by typing CONVTONURBS↵. This tool also converts 3D solids and meshes. To use it, follow these steps:
1. Open the CVedit1.dwg sample file, which can be obtained from the book’s companion website.
2. Make sure the NURBS option is on by typing SURFACEMODELINGMODE↵ 1↵.
3. Click the Extrude tool from the Surfaces – Create tool group on the Tool Sets palette.
4. Type MO↵ SU↵ to create an extruded surface.
5. Select the spline and press ↵.
6. Point the cursor upward and type 6↵ to make the extruded surface 6 units in the Z axis.
7. Select the NURBS surface.
8. In the Surface Associativity category in the Properties Inspector palette, select Maintain Associativity and None.
Exposing CVs to Edit a NURBS Surface
You’ve just created a NURBS surface. You can expose the CVs for the surface using the Show CV tool. Try the following to view and edit the CVs.
1. Select the NURBS surface.
2. In the Geometry category in the Properties Inspector palette, click the CV Hull check box. The CVs appear for the surface.
3. Click the CV as shown in Figure 23-50.
Figure 23-50:Exposing the CVs
4. Move the CV in the Y axis and notice how the surface deforms. The top edge moves with the CV, while the bottom edge maintains its shape.
5. Press the Esc key twice to clear your selection.
In this exercise, you saw how you can gain access to the CVs of a NURBS surface to make changes to the shape. Right now, the CVs are located only at the top and bottom of the surface, but you can add more CVs to give you more control over the shape of the surface.
Adding CVs to a NURBS Surface
The next exercise shows you how you can add additional CVs through the Rebuild option:
1. Click the surface to select it and then right-click and select NURBS Editing Rebuild. The Rebuild Surface dialog box appears (see Figure 23-51). You can also type CVREBUILD↵ or choose Modify Surface Editing NURBS Surface Editing Rebuild.
Figure 23-51:The Rebuild Surface dialog box
2. In the Control Vertices Count group of the Rebuild Surface dialog box, make sure the In U Direction option is set to 8 and the In V Direction option is set to 7.
The U direction is along the horizontal curve, while the V direction is along the straight, vertical curve. If you count the CVs in each row or column, you’ll see that they match the values you entered for U and V.
3. Click OK. Now you see that many more CVs are available.
Now if you were to move a CV, the surface is able to deform along the Z axis, where it remained a straight line before.
What Are the U and V Directions?
While working in 3D, you’ll see references to the U and V directions. You can think of these as the X and Y axes of a 3D surface. There is also a W direction, which corresponds to the Z axis, or the normal direction to a surface.
The Rebuild Surface dialog box offers a number of other options you’ll want to know about. Table 23-2 gives you a rundown.
Table 23-2: The Rebuild Surfaces dialog box options
| Option | Purpose |
| Control Vertices Count | |
| In U Direction | Sets the number of CVs in the U direction |
| In V Direction | Sets the number of CVs in the V direction |
| Degree | |
| In U Direction | Sets the number of CVs available per span in the U direction |
| In V Direction | Sets the number of CVs available per span in the V direction |
| Options | |
| Delete Original Geometry | Determines whether the original geometry is retained or not |
| Retrim Previously Trimmed Surfaces | Determines whether trimmed surfaces are retained from the original surface |
| Maximum Deviation | Displays the maximum deviation between the original and rebuilt surface |
Two other tools in the NURBS Editing shortcut menu allow you to either add or remove a set of CVs. The Add CV tool lets you place a row or column of CVs. The Remove CV tool will remove a row or column of CVs. Both options allow you to toggle between the U and V directions for the addition or removal by typing D↵.
The Add CV and Remove CV tools can be useful when you want to fine-tune the curvature of a surface. Where you want a “tighter” curve, you can add more CVs to an area of the surface. You can then move the CVs in the selected area to increase the curvature. To smooth out the curvature of an area, remove the CVs.
Editing with the 3D Edit Bar
You’ve seen how a NURBS surface can be set up to add additional CVs, which in turn allow you to adjust the shape of the surface. But the CVs by themselves allow you to adjust their pull on the surface only by moving the CVs closer to or farther away from the surface.
The 3D Edit bar gives you more control over the behavior of individual CVs. With the 3D Edit bar, you can change the strength and direction of the “pull” exerted by a CV.
Try the following exercise to see firsthand how the 3D Edit bar works:
1. Type 3DEDITBAR↵.
2. Select the NURBS surface. Now as you move the cursor across the surface, you see two red lines that follow the U and V directions of the surface (see Figure 23-52).
Figure 23-52:The 3D Edit bar’s U and V directions are shown by two red lines.
3. Click the point shown in Figure 23-52. A Move gizmo appears along with two other features called the magnitude handle and the expansion grip (see Figure 23-53).
Figure 23-53:The magnitude handle and expansion grip
The Move gizmo gives you a bit more control over the location of the CV since it allows you to isolate movement in the X, Y, or Z direction. The expansion grip lets you change the tangency of the CV, while the magnitude grip lets you control the strength of the CV.
Try the following steps to see how these two features work:
1. Click the expansion grip. Notice that the Move gizmo switches to the location of the expansion grip.
2. Hover over the green Y axis of the gizmo, and when you see the green Y axis vector, click and drag the mouse. Notice how the surface warps as you move the mouse. If you look carefully at the 3D Edit bar, you see that it pivots around the new location of the expansion grip, the CV location.
3. Press the Esc key to release the Y axis, and then click the expansion grip. The Move gizmo returns to its original location at the CV.
4. Now click the magnitude handle and move it horizontally. You see that the surface is “pulled” in both directions of the U axis of the surface.
5. Press the Esc key to release the magnitude handle.
6. Right-click on the 3D Edit bar and select V Tangent Direction. Notice that the magnitude handle changes its orientation so that it is aligned to the V direction of the surface.
7. Click and drag the magnitude handle to see how it affects the surface.
8. Press the Esc key twice to exit the 3D Edit bar.
As you can see from this exercise, the 3D Edit bar gives you much more control over a CV than you would have otherwise. You also saw the shortcut menu for the 3D Edit bar (see Figure 23-54) in step 6. The shortcut menu allows you to change the direction of the magnitude grip, but it also lets you switch the position of the Move gizmo and the expansion grip with the Move Point Location and Move Tangent Direction options. The Relocate Base Point option enables you to move to a different CV location. Table 23-3 includes descriptions of these options.
Figure 23-54:The 3D Edit bar’s shortcut menu
Table 23-3: The 3D Edit bar’s right-click menu options
| Option | Purpose |
| Move Point Location | Places the Move gizmo at the CV location |
| Move Tangent Direction | Places the Move gizmo at the expansion grip location to allow adjustment to the tangent direction of the CV |
| U Tangent Direction | Aligns the magnitude grip to the surface’s U direction |
| V Tangent Direction | Aligns the magnitude grip to the surface’s V direction |
| Normal Tangent Direction | Aligns the magnitude grip to a direction that is normal (perpendicular) to the surface |
| Set Constraint | Constrains changes to the tangency in a specific direction such as X, Y, or Z or in a plane defined by a pair of axes |
| Relocate Base Point | Moves the CV Edit bar to a different location on the surface |
| Align Gizmo With | Aligns the gizmo with the world or current UCS or with a face on the surface |
Using the 3D Object Snaps
You may have noticed the 3D Object Snap button in the status bar when it is expanded.
This tool works in a way that is similar to how the Object Snap button you’ve used in earlier chapters works. When the 3D Object Snap button is on, you can snap to geometry on 3D objects. If you right-click this button, you’ll see the list of locations you can snap to.
You can think of the 3D Object Snap button as an extension of the standard set of object snaps that allow you to pick locations on 3D solids, meshes, and surfaces. Right-click on the 3D Object Snap button and choose Settings and you will see the Drafting Settings dialog box open to the 3D Object Snap tab. There you can choose which 3D object snap you want to appear as the default when this tool is turned on.
Making Holes in a Surface with the Project Geometry Tool
Eventually, you’ll need to place an opening in a surface, so AutoCAD offers the Project Geometry tool. This tool allows you to project a closed 2D object’s shape onto a 3D surface. For example, if you want to place a circular hole in the surface you edited in the previous exercise, you would draw a circle parallel to that surface and then use the Surface Projection UCS tool.
Try the following exercise to see how the Project Geometry tool works:
1. From the Layers palette, turn on the Circle layer. A circle appears in the drawing.
2. Type UCS↵ and then type OB↵. This lets you align the UCS to an object.
3. Click the circle to align the UCS to the circle.
4. Type SURFACEAUTOTRIM↵ 1↵ to turn Autotrim on.
5. Type PROJECTGEOMETRY↵ PRO↵ U↵.
6. Click the circle and press ↵.
7. Click the surface. The circle is projected onto the surface and the area inside the projected circle is trimmed (Figure 23-55).
Figure 23-55:The circle projected onto the surface
In this exercise, you aligned the UCS to the circle. The Project Geometry tool you used in step 5 projected the circle in the Z axis of this new UCS that is aligned with the circle.
The other two Project Geometry options use different criteria to project geometry. The View option will project geometry along the line of sight. If you had used this tool in the previous exercise, the projected circle and opening would appear directly behind the circle from your current view. The Points (or Vector) option projects geometry along a vector that you indicate with two points. You can use the 3D object snaps to select points on the geometry and the surface.
Visualizing Curvature: Understanding the Surface Analysis Tools
In addition to the surface editing tools, AutoCAD offers several surface analysis options. These options offer some visual aids to help you see the curvature of your surface’s models more clearly. They can be found under the Analysis tool group on the Tool Sets palette and are called Zebra Analysis, Draft Analysis, and Curvature Analysis.
Zebra Analysis displays stripes that allow you to better visualize how the curvature of surfaces blend. The smoother the stripes, the better the transition between surfaces.
Curvature Analysis displays colors to indicate the direction and amount of curvature in a surface. A negative curvature is a saddle shape and displays a blue color. A positive curvature, or bowl shape, displays in red.
Draft Analysis displays colors to help you determine draft angles. Draft angles are often used in the design of objects that are to be cast from a mold and are important in allowing the cast object to be easily removed from the mold.
The Analysis Options tool opens the Analysis Options dialog box, which enables you to control the way the different analysis tools are displayed. You must use a visual style other than Wireframe.
Create a simple 3D mesh. Mesh modeling allows you to create more organic 3D forms by giving you unique smoothing and editing tools. You can start your mesh model by creating a basic shape using the mesh primitives.
Master It Name at least six mesh primitives available on the Primitives submenu under Draw 3D Modeling Meshes on the menu bar.
Edit faces and edges. The ability to edit faces and edges is essential to creating complex shapes with mesh objects.
Master It Name the tool that is used to divide a face into multiple faces.
Create mesh surfaces. The Mesh primitives let you create shapes that enclose a volume. If you just want to model a smooth, curved surface in 3D, you might find the surface mesh tools helpful.
Master It How many objects are needed to use the Edge Surface tool?
Convert meshes to solids. You can convert a mesh into a 3D solid to take advantage of many of the solid-editing tools available in AutoCAD.
Master It Name at least two tools you can use on a solid that you cannot use on a mesh.
Understand 3D surfaces. 3D surfaces can be created using some of the same tools you use to create 3D solids.
Master It Name at least two tools you can use to create both 3D solids and 3D surfaces.
Edit 3D surfaces. AutoCAD offers a wide range of tools that are unique to 3D surfaces.
Master It Name at least four tools devoted to CV editing.