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CHAPTER 17
Modeling in 3D

The AutoCAD^® program has three different 3D modeling toolsets comprising surfaces, solids, and meshes, reflecting the historical evolution of computer graphics. Each toolset was initially developed to suit specific industries: surfaces for industrial design, solids for engineering, and meshes for games and movies. Each toolset has its particular strengths and limitations that become evident the more you use it. Yet AutoCAD allows you to pick the best tool for the job no matter what type of work you do so that you can find the best solutions for your models.

In this chapter, you’ll learn to do the following:

Create surface models
Edit surface models
Create solid models
Edit solid models
Smooth mesh models
Live-section models

Create Surface Models

In this chapter, you will create a conceptual model of the O2 Arena in London, the same model used in Chapter 16, “Navigating 3D Models.”

In AutoCAD, surfaces are defined as infinitely thin shells that do not contain any mass or volume. To create surfaces in this chapter, you’ll use two-dimensional profile shapes (provided as part of this chapter’s companion files, available for download from the book’s web page at www.sybex.com/go/autocad2016essentials). You will begin the following exercise by creating a planar surface and then revolving, sweeping, and extruding 2D profiles into 3D surfaces.

Exercise 17.1: Make Planar Surfaces

Planar surfaces differ from flat bounded areas like circles and closed polylines in that they display surfaces rather than edges only, in shaded visual styles. Open the file Ex17.1-start.dwg from this chapter’s companion files available on this book’s web page.

images

Select the 3D Modeling workspace from the Quick Access toolbar.
Select the ribbon’s Home tab if it is not already selected and click the Make Current tool in the Layers panel. Select the circle at the center of the drawing to set the Dome Membrane layer as current.

Like dimensions, surfaces can optionally be associated with the profile shapes that define them. Altering the shape of a profile immediately changes the form of its associated surface.
Select the ribbon’s Surface tab and click the Surface Associativity toggle in the Create panel if it is not already highlighted in blue.
Select the Planar tool in the Create panel. The command prompt reads as follows:
```
PLANESURF Specify first corner or [Object] <Object>:
```
Press Enter to accept the default Object option. Select the blue circle at the center of the drawing and press Enter. A planar surface appears as the PLANESURF command ends.
Click the SW corner of the ViewCube^® to move to a SW isometric viewpoint. The blue planar surface you just created is visible at the top of the dome (see Figure 17.1).

Your model should now resemble Ex17.1-end.dwg.

Exercise 17.2: Revolve a 2D Profile to Create a 3D Model

Much like you would turn wood on a lathe, you create 3D surfaces by revolving open profiles such as lines, arcs, or polylines around an axis. In the following steps, you will revolve a single arc to generate the exterior surface of the dome. To begin, open Ex17.2-start.dwg from this chapter’s companion files.

images

Select the ribbon’s Surface tab and toggle off the Surface Associativity icon in the Create panel.
Select the Revolve tool on the Create panel of the ribbon’s Surface tab. Select the blue arc running from the planar surface at the top of the dome down to the white circle at the periphery and press Enter.
The command prompt reads as follows:

The dome is centered on the origin point in the sample file.
```
REVOLVE Specify axis start point or define axis by [Object X Y Z]
<Object>:
```
Type 0,0 and press Enter.
The command prompt now reads as follows:
```
REVOLVE Specify axis endpoint:
```
Type 0,0,1 and press Enter. Press Enter again to accept the default angle of revolution (360 degrees). The REVOLVE command ends, and the dome surface appears (see Figure 17.2).

Figure 17.2 Revolving an arc to generate the dome surface
Type E (for Erase) and press Enter. Type P (for Previous) and press Enter. Press Enter again to erase the arc that generated the dome surface.

THREE-DIMENSIONAL CARTESIAN COORDINATES

The Z direction extending above and below the ground plane can be specified within Cartesian coordinates simply by adding a second comma followed by the Z value. For example, the coordinates of a point one unit above the origin point are 0,0,1.
Type LA (for Layer) and press Enter to open the Layer Properties Manager. Double-click the icon representing the Arena layer to set it as current.
Click the Dome Membrane layer’s lightbulb icon to toggle it off.
Click the Auto-hide toggle so that the palette collapses when the cursor isn’t over it (see Figure 17.3).

Your model should now resemble Ex17.2-end.dwg.

Exercise 17.3: Sweep Out 3D Geometry

The SWEEP command gives you the ability to create surfaces by pushing an open profile through space following a path. In these steps, you will model the area within the O2 Arena and its internal roof by sweeping open shapes along closed paths. To begin, open Ex17.3-start.dwg from this chapter’s companion files.

Select the Sweep tool on the Create panel of the ribbon’s Surface tab. Select the green arena profile shown in Figure 17.4 and press Enter.

Figure 17.4 Profiles and sweep paths representing the O2 Arena
The command prompt reads as follows:
```
Select sweep path or [Alignment Base point Scale Twist]:
```
Select the arena sweep path as shown in Figure 17.4. Figure 17.5 shows the resulting 3D arena.
Hover the cursor over the Layer Properties Manager’s title bar to reveal the palette. Double-click the Arena Roof layer’s icon to set it as current.
Press the spacebar to repeat the SWEEP command. Select the arena roof profile and press Enter. Select the arena roof sweep path. Figure 17.6 shows the result.

The O2 Arena dome stretches over the arena roof and the entire O2 complex.
Hover the cursor over the Layer Properties Manager’s title bar to reveal the palette. Double-click the Dome Edge layer’s icon to set it as current. Toggle off the Arena and Arena Roof layers.

Your model should now resemble Ex17.3-end.dwg.

Exercise 17.4: Extrude 2D Geometry into 3D

Extruding means pushing forcibly through a die, like hot steel beams being extruded at a foundry. In the following steps, you will extrude the boundary representing the edge of the dome membrane as a curtain-like wall. In the next section, you will use this curtain to trim off the outer portion of the membrane. To begin, open Ex17.4-start.dwg from this chapter’s companion files.

Select the Extrude tool on the Create panel of the ribbon’s Surface tab. Select the magenta dome edge (see Figure 17.7) and press Enter.

Figure 17.7 Selecting the dome edge
The command prompt reads as follows:
```
Specify height of extrusion or [Direction Path Taper angle]
```
Type 50 and press Enter. A 3D curtain-like wall rises up out of the 2D edge.
Hover the cursor over the Layer Properties Manager’s title bar to reveal the palette. Toggle on the Dome Membrane layer. Double-click the Dome Membrane layer’s icon to set it as current. Figure 17.8 shows the result.

Your model should now resemble Ex17.4-end.dwg.

Edit Surface Models

Surface models have editing tools that modify existing surface boundaries. In the following sections, you will modify surface boundaries by using other surfaces or by projecting edges onto existing surfaces and using these projections to modify boundaries or cut holes in surfaces. In addition, you will project 2D objects onto 3D surfaces without altering the surfaces at all.

Exercise 17.5: Trim Surfaces with Other Surfaces

In the following steps, you will trim off the portion of the dome membrane that extends beyond the curtain wall extrusion you generated in the previous section. To begin, open Ex17.5-start.dwg from this chapter’s companion files.

Switch to the 3D Modeling workspace if it’s not selected already in the Quick Access toolbar.
Select the Trim tool on the Edit panel of the ribbon’s Surface tab. The command prompt reads as follows:
```
SURFTRIM Select surfaces or regions to trim or
[Extend PROjection direction]:
```
Click point A in Figure 17.8 and press Enter.
The command prompt now reads as follows:
```
SURFTRIM Select cutting curves, surfaces, or regions:
```
Click point B in Figure 17.8 and press Enter.
The prompt reads as follows:
```
SURFTRIM Select area to trim [Undo]:
```
Click point C in Figure 17.8 and press Enter. The SURFTRIM command ends.
Hover the cursor over the Layer Properties Manager’s title bar to reveal the palette. Click the Sun icon to freeze the Dome Edge layer. Figure 17.9 shows the resulting trimmed dome membrane.

Your model should now resemble Ex17.5-end.dwg.

Exercise 17.6: Project Edges on Surfaces

In the following steps, you will project a series of 2D objects onto a 3D surface. More specifically, you will project the large hole for the ventilation towers, 12 smaller holes accommodating the structural masts, and numerous cables onto the surface of the dome membrane. To begin, open Ex17.6-start.dwg from this chapter’s companion download.

Using the in-canvas controls in the top-left corner of the viewport, click the Visual Style menu and select Wireframe. (You want to see through the dome but cannot in the Shaded With Edges visual style.)
Hover the cursor over the Layer Properties Manager’s title bar to reveal the palette. Double-click the Dome Voids layer’s icon to set it as current.
Zoom into the area where there is a large orange circle with a series of light blue circles and ellipses inside it.
Toggle on Auto Trim in the Project Geometry panel.
Select the Project To UCS tool in the Project Geometry panel on the ribbon’s Surface tab. The command prompt reads as follows:
```
PROJECTGEOMETRY Select curves, points to be projected or
[PROjection direction]:
```
Click the large orange circle and press Enter.
The command prompt now reads as follows:
```
PROJECTGEOMETRY Select a solid, surface, or region for
the target of the projection:
```
Select the blue dome membrane. A new orange spline appears on the surface of the trimmed dome (see Figure 17.10), and the PROJECTGEOMETRY command ends.

Figure 17.10 Projecting the ventilation tower cutout upward onto the dome membrane’s surface
Type E (for Erase) and press Enter. Click points A and B in Figure 17.10 to create a crossing window that selects both the dome and the projected spline.
Type R (for Remove) and press Enter.
Type L (for Last) and press Enter twice to erase the projected spline but not the dome.
Pan over to the small orange circle with a white line running through it.

You will array this projected spline around the dome in the next section.
Toggle off Auto Trim in the Project Geometry panel.
Select the Project To UCS tool in the Project Geometry panel, select the small orange circle, and press Enter. Select the blue dome. A new projected spline appears on the dome surface (see Figure 17.11).

Figure 17.11 Projecting one mast void upward onto the dome membrane’s surface
Type E (for Erase) and press Enter. Select the original small orange circle on the ground and press Enter.
Select the ribbon’s Home tab and click the Isolate tool in the Layers panel. Type S (for Settings) and press Enter. Type O (for Off) and press Enter twice. Select the blue dome membrane and press Enter.
Hover the cursor over the Layer Properties Manager’s title bar to reveal the palette. Click the Cables layer’s snowflake and darkened lightbulb icons both to thaw and to toggle the layer on. Double-click the Cables layer’s icon to set it as current (see Figure 17.12).

Figure 17.12 Changing layer states
Click the Top of the ViewCube. Click the Rotate Clockwise icon in the ViewCube interface if necessary so North is up.
Select the ribbon’s Surface tab and click the Project To View tool in the Project Geometry panel. Select all the objects in the drawing canvas with a crossing selection and press Enter. The command prompt reads as follows:
```
PROJECTGEOMETRY Select a solid, surface, or region for
the target of the projection:
```
Select the blue dome. Although the PROJECTGEOMETRY command ends, you can’t see the projected objects in the top view.
Click the Front arrow below the ViewCube. Type E (for Erase) and click points A and B in Figure 17.13 to select all the lines on the ground. Press Enter to erase the selection.

Figure 17.13 Selecting lines on the ground in the Front view for deletion
Click the upper-left corner of the ViewCube to switch into an SW Isometric viewpoint. Type LAYUN (for Layer Unisolate) and press Enter.

Your model should now resemble Ex17.6-end.dwg.

Exercise 17.7: Trim Surfaces with Edges

You already trimmed one surface when you projected the large orange circle onto the dome using Auto Trim mode in the previous section. You won’t use Auto Trim in the next exercise because you need to retain the projected object. In the following steps, you will first array this projected spline around the dome and then manually trim all 12 voids through which the structural masts will ultimately pass. To begin, open Ex17.7-start.dwg from the companion files.

Hover the cursor over the Layer Properties Manager’s title bar to reveal the palette. Click the Dome Voids layer’s darkened lightbulb icon to toggle on this layer.
Type AR (for Array), press Enter, select the small orange spline that you projected on the dome in the previous section, and press Enter. Type PO (for Polar) and press Enter. The command prompt reads as follows:
```
ARRAY Specify center point of array or
[Base point Axis of rotation]:
```
Type 0,0 and press Enter.
The command prompt now reads as follows:
```
ARRAY Select grip to edit array or [Associative Base point Items Angle between Fill angle ROWs Levels ROTate items eXit]<eXit>:
```
You cannot trim a surface with an array object. By making a nonassociative array, you end up with individual objects that can be used.

Type I (for Items) and press Enter. Type 12 and press Enter. Type AS (for Associative), type N (for No), and press Enter. Press Enter to end the ARRAY command. Twelve splines appear arrayed around the dome (see Figure 17.14).

Figure 17.14 Arraying projected splines around the dome
Open the in-canvas Visual Style Controls menu and select Shaded With Edges.
Select the Trim tool on the Edit panel of the ribbon’s Surface tab. Select the dome, press Enter, select one of the orange splines, and press Enter. Click inside the spline and press Enter. A hole in the shape of the spline is cut in the dome.
Repeat the previous step 11 times, one for each remaining orange spline.
Hover the cursor over the Layer Properties Manager’s title bar to reveal the palette. Click the Cylindrical Towers layer’s darkened lightbulb icon to toggle this layer on and then double-click the layer’s icon to set it as current. Toggle off the Dome Voids layer. Figure 17.15 shows the result.

Your model should now resemble Ex17.7-end.dwg.

Create Solid Models

If surfaces cover 2D floor spaces, then solid models enclose 3D volumes. Only with solid objects can you use the MASSPROP command to calculate engineering properties such as volume, centroid, moments of inertia, and so on. Many of the solid modeling tools are the same as the surface modeling tools. If you start these commands with a closed path such as a circle, ellipse, or closed polyline, you will end up with a solid object, whereas open paths generate surfaces. In the following sections, you’ll extrude and loft solid objects.

Exercise 17.8: Extrude Solid Objects

The difference between a surface extrusion and a solid extrusion is what’s in the middle: nothing in the case of the surface model and “mass” in the case of the solid. In the next section, you’ll see how to affect the solid “mass” with Boolean tools. In the following steps, you’ll extrude a circle into a solid and array it around the dome. To begin, open Ex17.8-start.dwg from this chapter’s companion files.

Switch to the 3D Modeling workspace if it’s not selected already in the Quick Access toolbar.
Select the ribbon’s Solid tab and click the Extrude tool in the Solid panel. Select the cyan circle at the edge of the dome and press Enter. The command prompt reads as follows:
```
EXTRUDE Specify height of extrusion or [Direction Path Taper angle]
<50.000>:
```
Type 30 and press Enter. The 2D circle becomes a 3D solid cylinder.
The O2 Arena features cylindrical towers in pairs. Type MI (for Mirror) and press Enter. Type L (for Last) and press Enter twice. The command prompt reads as follows:
```
MIRROR Specify first point of mirror line:
```
Type 0,0 and press Enter.
The command prompt now reads as follows:
```
MIRROR Specify second point of mirror line:
```
Type 0,1 to specify a mirror line running along the y-axis and press Enter. Press Enter once more to accept the default (not to erase the source objects). Figure 17.16 shows the resulting pair of cylinders.

When you are specifying the mirror line, only its direction matters—the distance and units do not.
You need to place six pairs of cylinders around the dome. Type AR (for Array) and press Enter. Select both cylindrical towers and press Enter. Type PO (for Polar) and press Enter. The command prompt reads as follows:
```
ARRAY Specify center point of array or
[Base point Axis of rotation]:
```
Type 0,0 and press Enter. Type I (for Items) and press Enter. Type 6 (for the number of items) and press Enter. Press Enter to accept the default and end the ARRAY command. Figure 17.17 shows the result.

Figure 17.16 Extruding and mirroring one pair of solid cylindrical towers

Figure 17.17 Arraying pairs of cylindrical towers around the dome
Switch to Wireframe using the in-canvas Visual Style Controls menu so that you can see through the dome.
Hover the cursor over the Layer Properties Manager’s title bar to open the palette. Toggle on the Masts layer. Double-click the Masts layer to set it as current. Zoom into the yellow vertical line with a hexagon around its midpoint; this represents a structural mast.
Click the Extrude tool in the Solid panel. Select the hexagon at the midpoint of the vertical line and press Enter. The command prompt reads as follows:
```
EXTRUDE Specify height of extrusion or
[Direction Path Taper angle] <30.000>:
```
Type T (for Taper Angle) and press Enter.

Profiles of extruded items are automatically deleted.
The command prompt now reads as follows:
```
EXTRUDE Specify angle of taper for extrusion <15.00>:
```
Type 1 and press Enter. Toggle on Endpoint object snap if it is not already running and click the top endpoint of the vertical line to specify the height of the extrusion. Figure 17.18 shows the result.

The extracted edges are coincident with the original edges of the solid object.

Figure 17.18 Extruding half of a tapering hexagonal solid mast
Select the Extract Edges tool on the Solid Editing panel, select the mast, and press Enter. The Extract Edges tool creates wireframe geometry for solid objects.
Zoom in on the hexagonal bottom of the mast. Type J (for Join) and press Enter. Click points A and B shown in Figure 17.19 to create a crossing window that selects the lines, making a hexagon, and press Enter.

Figure 17.19 Joining six edges to form a hexagonal polyline
Select the Extrude tool in the Solid panel, type L (for Last), and press Enter twice.

You will unify, rotate, and array the masts around the dome in the “Edit Solid Models” section.

The ventilation towers serve a pair of road tunnels passing under the Thames in London. These towers were in situ prior to the construction of the O2 Arena.
Type T (for Taper Angle), press Enter, and then press Enter again to select the default one-degree taper angle. Zoom and click the lower endpoint of the vertical yellow line to extrude the lower half of the mast down to the ground.

Your model should now resemble Ex17.8-end.dwg.

Exercise 17.9: Loft Solid Objects

Lofting is a modeling technique that lets you create a 3D model from a series of 2D cross sections. In the following steps, you will loft two ventilation towers from a series of circles and ellipses. To begin, open Ex17.9-start.dwg from this chapter’s companion files.

Hover the cursor over the Layer Properties Manager’s title bar to open the palette. Toggle on Ventilation Towers and then double-click the layer to set it as current. Toggle off the Dome Membrane and Cables layers.
Switch to Shaded With Edges using the in-canvas Visual Style Controls menu.
Zoom in on the collection of blue circles and ellipses. Select the Loft tool from the drop-down menu under Sweep on the Solid panel and press Enter. Select profiles A, B, C, and D shown in Figure 17.20 and press Enter twice. Select the loft object, open the grip menu that appears, choose Normal To Start And End Sections, and press Esc.

Normal means perpendicular to the surface in question.

Figure 17.20 Lofting one of the two ventilation towers
Press the spacebar to repeat the LOFT command. Select profiles E, F, G, and H, shown in Figure 17.20, and press Enter twice. Select the new loft object, open the grip menu that appears, choose Normal To Start And End Sections, and press Esc. Figure 17.21 shows the result.

Your model should now resemble Ex17.9-end.dwg.

Edit Solid Models

Solid-editing tools provide an alternative set of modeling possibilities as compared with surface tools. Boolean tools (named after mathematician George Boole) allow you to unify, subtract, and intersect solids (set theory terms) to create new forms. You will explore these tools in the following section and learn about a variety of specialized solid-editing tools.

Exercise 17.10: Perform Boolean Operations

In the following steps, you will unify the top and bottom parts of the mast with the UNION command. You will then rotate and array 12 masts around the dome. To begin, open Ex17.10-start.dwg from among the companion files.

Switch to the 3D Modeling workspace if it’s not selected already in the Quick Access toolbar.
Switch to Wireframe using the in-canvas Visual Style Controls menu.
Select the Union tool in the Boolean panel, click the left and right ventilation towers, and press Enter. A curve representing the precise intersection of these two forms’ surfaces appears in the wireframe representation (see Figure 17.22).

Figure 17.22 Wireframe representations of two separate lofted ventilation towers (left) and a single object (right) created with Boolean union
Pan over to the mast objects you extruded in the previous section. Hover the cursor over the Layer Properties Manager’s title bar to open the palette. Double-click the Masts layer to set it as current.
Select the Union tool in the Boolean panel. Drag a crossing window through both mast solids to select them and press Enter. Although nothing has changed visually, the two solids have been unified as a single object. Zoom into the base of the mast.
Select the ribbon’s Home tab and click the 3D Rotate tool in the Modify panel. Select the mast and press Enter. Click the lower endpoint of the vertical line, which is at the center of the mast, to act as the base point. A 3D rotate gizmo appears (see Figure 17.23).
Click the red ring to select the x-axis. The command prompt reads as follows:
```
3DROTATE Specify angle start point or type an angle:
```
Type -14, and press Enter.
Click the 3D Rotate tool in the Modify panel again; then select the mast and press Enter. Click the same base point shown in Figure 17.23 and click the green axis ring to select the y-axis. Type 4 and press Enter.

Figure 17.23 3D rotate gizmo displaying three colored rings representing the x-, y-, and z-axes
Zoom out and select the Erase tool in the Modify panel. Select the edges you extracted from the mast in the previous section and the vertical mast line (see Figure 17.24) and press Enter.

Figure 17.24 Erasing the edges extracted earlier
Type AR (for Array) and press Enter. Select the solid mast and press Enter. Type PO (for Polar) and press Enter. Type 0,0 (as the center point of the array) and press Enter.
Type I (for Items) and press Enter. The command prompt reads as follows:
```
ARRAY Enter number of items or [Angle between Expression] <4>:
```
Type 12 and press Enter two more times to complete the command.
Hover the cursor over the Layer Properties Manager’s title bar to reveal the palette. Toggle on the Dome Membrane layer. Switch to Shaded With Edges using the in-canvas Visual Style Controls menu. Zoom out to view the entire model. Figure 17.25 shows the result.

Your model should now resemble Ex17.10-end.dwg.

Exercise 17.11: Edit Solids

Rather than edit a whole solid object, it is possible to select parts of the object (called subobjects) for editing. In the following steps, you will offset a subobject, create an interior shell, and then use AutoCAD’s Presspull tool on two faces to perform an automatic Boolean subtraction. To begin, open Ex17.11-start.dwg from this chapter’s companion files.

images

Select the Isolate tool in the Layers panel, type S (for Settings), and press Enter. Type O (for Off) and press Enter twice. Select the ventilation towers and press Enter. Zoom into the ventilation towers.
Select the ribbon’s Solid tab and then select the Offset Edge tool in the Solid Editing panel. Click the top face of the left tower. The command prompt reads as follows:
```
OFFSETEDGE Specify through point or [Distance Corner]:
```
Type D (for Distance) and press Enter. Type 1 and press Enter.
The command prompt now reads as follows:
```
Specify point on side to offset:
```
Click the center of the top-left face to offset the edge internally. Click the top face of the right tower. Type D (for Distance) and press Enter. Type 1 and press Enter. Click the center of the top-right face and press Enter to end the OFFSETEDGE command. Figure 17.26 shows the result.
Switch to Wireframe using the in-canvas Visual Style Controls menu.
Select the Shell tool on the right side of the Solid Editing panel. Select the side of the ventilation towers (not the offset top faces) and press Enter. Type 1 (the same distance you offset in the previous step) and press Enter twice to end the SOLIDEDIT command. A hollow interior shell is generated within each ventilation tower. However, the tops are still solid because the shell is inset 1 unit from all sides (including the top).
Select the Presspull tool on the Solid panel. Click point A in Figure 17.27, keep the cursor above the towers, type -1, and press Enter. Click point B, type -1, and press Enter twice.

Figure 17.26 Offsetting edges on the tops of the ventilation towers

Figure 17.27 Using Presspull to remove the tops of the ventilation towers
Switch to Shaded With Edges using the in-canvas Visual Style Controls menu. Now you can see the voids you cut in the tops of the ventilation towers in the previous step.
Type LAYUN (for Layer Unisolate) and press Enter.
Select the Thicken tool on the Solid Editing panel. Select the dome membrane and press Enter. The command prompt reads as follows:
```
THICKEN Specify thickness <1.000>
```
Type -0.5 and press Enter. The dome surface thickens into a solid shell (see Figure 17.28).

Your model should now resemble Ex17.11-end.dwg. Figure 17.29 shows the completed 3D model.

Smooth Mesh Models

Mesh objects are represented by discrete polygonal surfaces that can be smoothed, meaning their geometrical forms can be rounded out. Mesh objects are ideal for representing organic or sculptural forms.

Exercise 17.12: Create, Edit, and Smooth Mesh

In the following steps you will create a mesh object, edit its faces, smooth, and refine it. To begin, open Ex17.12-start.dwg from this chapter’s companion files.

Switch to the 3D Modeling workspace if it is not already selected in the Quick Access toolbar.
Zoom into the area to the left of the Ventilation towers.
Select the Mesh panel on the ribbon and click the Mesh Box tool. Click an arbitrary first corner point somewhere to the left of the ventilation towers. Type 20, press Tab, type 7, and press Enter. Move the cursor above the object, type 5, and press Enter to specify the height of the mesh box (see Figure 17.30).

Figure 17.30 Creating a mesh box
Click the Extrude Face tool in the Mesh Edit panel, select the three faces on the top right of the mesh object, and press Enter. Type 5 and press Enter to extrude the selected faces (see Figure 17.31).

Figure 17.31 Extruding selected mesh faces
Click the Smooth More tool in the Mesh panel, select the mesh object, and press Enter. Repeat this procedure to smooth the mesh even more (see Figure 17.32).

Figure 17.32 Smoothing a mesh object twice
Click the Refine Mesh tool in the Mesh panel, select the mesh object, and press Enter. A denser, smoother mesh is the result (see Figure 17.33).

Your model should now resemble Ex17.12-end.dwg.

Live-Section Models

A section is a cut through a 3D model displaying 2D line work where the model and cutting plane intersect. A live section is a dynamic cutting plane that you can move in relation to the model, helping you visualize the model’s interior with a combination of 2D and 3D geometry. In AutoCAD 2016 there are now four types of live section cuts: plane, slice, boundary, and volume.

Exercise 17.13: Create and Edit a Section Plane

Let’s create a section plane and then move it to see the dynamic feature. To begin, open Ex17.13-start.dwg from this chapter’s companion files.

Switch to the 3D Modeling workspace if it is not already selected in the Quick Access toolbar.

Live sectioning uses your computer’s graphics card processor. It might not work properly if your hardware is not recommended at www .autodesk.com/ graphics-hardware.
On the ribbon’s Home tab, click the Section Plane tool in the Section panel. With Ortho mode on, click points A and B shown in Figure 17.34 to create a vertical section plane.

Figure 17.34 Drawing a section plane
Move the section plane over a short distance so that it still intersects the model and observe that the live section automatically updates.
Open the downward-facing triangular grip and select Slice from the context menu that appears. Type 0.5 in the Slice Thickness text box in the ribbon’s Adjust panel that appears while you have the Section Object selected. A 3D slice is all that is visible of the object (see Figure 17.35).

Figure 17.35 Configuring a 3D slice
Change the grip menu to Volume and then adjust the top and left grips to describe a volume less than the total volume of the object. The object is sliced along three planes.
Select the section object, type SECTIONPLANESETTINGS, and press Enter. Change the color under Intersection Boundary to Green. Under Intersection Fill, change Face Hatch to Predefined/ANSI31 and change Hatch Scale to 6. Scroll down; under Cut-Away Geometry, change Show to Yes, Color to Red, and Face Transparency to 80. The result shows the intersection boundary as a thin green line, the intersection fill with a cross-hatch pattern, and the cutaway geometry in transparent red (see Figure 17.36). Click OK.

Figure 17.36 Changing the appearance of a live section
Select the section object. Open the Isolate Objects control on the status bar and select Hide Objects from the menu that appears.

Your model should now resemble Ex17.13-end.dwg.

Prev Next

CHAPTER 17 Modeling in 3D

Create Surface Models

Exercise 17.1: Make Planar Surfaces

Exercise 17.2: Revolve a 2D Profile to Create a 3D Model

Exercise 17.3: Sweep Out 3D Geometry

Exercise 17.4: Extrude 2D Geometry into 3D

Edit Surface Models

Exercise 17.5: Trim Surfaces with Other Surfaces

Exercise 17.6: Project Edges on Surfaces

Exercise 17.7: Trim Surfaces with Edges

Create Solid Models

Exercise 17.8: Extrude Solid Objects

Exercise 17.9: Loft Solid Objects

Edit Solid Models

Exercise 17.10: Perform Boolean Operations

Exercise 17.11: Edit Solids

Smooth Mesh Models

Exercise 17.12: Create, Edit, and Smooth Mesh

Live-Section Models

Exercise 17.13: Create and Edit a Section Plane

AutoCAD 2016® and AutoCAD LT® 2016

CHAPTER 17
Modeling in 3D