508 Part V: On a 3D Spree

Figure 22-11: Revolving a closed object around an axis.

Modifying 3D Objects

Many of the modification techniques and commands that you use in 2D drafting can be applied to 3D modeling. In addition, a specialized set of 3D editing commands is available. All these commands are located on the Modify panel of the Home tab when the 3D Modeling workspace is current.

Selecting subobjects

3D objects themselves are complex objects that can be made up of several hundred — even thousands — of objects. Although these objects never stray from their parent, you can access them individually or in groups through subobject selection. Subobject selection means selecting a vertex, edge, or face of a 3D object. After you select a subobject, you can use grip editing and the 3D gizmos to manipulate it. We discuss the 3D gizmos in the following section.

To make it easier to select subobjects, you can enable subobject filtering from the Ribbon. Vertex, edge, and face filters are located on the Subobject Selection Filter split button on the Selection panel of the Home and Solid tabs.

The CULLINGOBJ and CULLINGOBJSELECTION system variables help limit object selection to the faces that are visible in the current view by ignoring faces around the back of the objects being viewed. By default, both of these variables are turned off, so you can select objects in front and behind. If you have a complex model, turn culling on. To turn culling on, click Culling on the Selection panel of the Home tab. To turn it off, click the Culling button again. The button is shaded blue when the feature is enabled.

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If you just need to select a face on a 3D object, press and hold the Ctrl key and select the face you want to select. This can be faster than turning subobject filters on and off.

Working with gizmos

Although you can use the MOVE, ROTATE, and SCALE commands to modify 3D objects, they can sometimes give unexpected results in 3D. Enter the 3DMOVE, 3DROTATE, and 3DSCALE commands, which all use a gizmo or grip tool when a non-orthographic view is current (see Figure 22-12).

Figure 22-12: Using gizmos to modify objects in 3D.

The gizmos restrict or constrain movement along the X,Y plane and the Z axis. To use a gizmo, click one of the axes on the tool to restrict movement to that axis. You can access the three gizmos by using the following methods:

3DMOVE: Click 3D Move on the Home tab’s Modify panel, or type 3DMOVE at the command line.

3DROTATE: Click 3D Rotate on the Modify panel (Home tab), or type 3DROTATE at the command line.

3DSCALE: Click 3D Scale on the Modify panel, or type 3DSCALE at the command line.

You can also access the Move, Rotate, and Scale gizmos in 3D by selecting objects when no command is active. You can set the default gizmo that is displayed when you use grips in 3D by opening the Gizmo drop-down in the Home tab’s Selection panel and selecting the gizmo you want to be active. Right-clicking over a gizmo allows you to switch between different gizmos and constraints.

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510 Part V: On a 3D Spree

More 3D variants of 2D commands

Moving, rotating, and scaling objects are certainly the big-three operations of 3D editing, but a number of other 3D variations on 2D editing commands are hiding in the wings, awaiting their turn in the spotlight. For more about spotlights, see Chapter 23.

Getting your 3D ducks in a row

Getting objects to align with each other in 3D can be a challenge at times, especially if you need to not only move an object in 3D, but also rotate and scale it based on the specified alignment. AutoCAD has two commands that can be used to align objects:

ALIGN: Used to align 2D and 3D objects based on one, two, or three pairs of points. Based on the number of pairs of points specified and how they’re selected, the ALIGN command might move and rotate the selected objects into place. It can also be used to scale objects as well. On the Home tab, choose Align from the Modify panel slideout.

3DALIGN: An improved version of the ALIGN command that includes additional options, as well as the ability to move and rotate a copy of the selected objects and use Dynamic UCS with the command. Click 3D Align on the Modify panel of the Home tab.

Holding up a mirror

The MIRROR command is limited to working on the X, Y plane. If you want to mirror objects in 3D, you need to use the MIRROR3D command. Click 3D Mirror on the Modify panel of the Home tab. The MIRROR3D command is similar to the MIRROR command, but you can control the plane on which the mirroring is performed.

Associative arrays, which we discuss in Chapter 18, work in 3D as well as 2D. AutoCAD has long had a 3DARRAY command; it’s still there, and is similar to the old style ARRAY command (refer to Chapter 11 for that one) in that it doesn’t create an associative array object. For information on creating rectangular, polar, and path array objects, refer to the online help.

Editing solids

3D solids can be edited in a variety of different ways that other objects can’t be. You can use grip editing to change the shape of 3D solids, or Boolean operations on a 3D solid to create complex models. You can fillet and chamfer the edges of a 3D solid by using the FILLETEDGE and CHAMFEREDGE commands.

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Using grips to edit solids

Grip editing is one of the most direct ways to modify an object. To edit a 3D solid by using grips, select the 3D solid when no command is running, and then select the grip you want to use to edit the solid. Pay close attention to the grip you select; some grips give you control over changing the overall size of a solid; others might change only part of a solid, such as the face or top radius of a cone. Figure 22-13 shows a pyramid with its top radius (I’ll bet you didn’t know that pyramids had radii!) being edited with grips.

Figure 22-13: Grip editing a pyramid.

Boolean operations

As we mention in the “Drawing solid primitives” section, earlier in this chapter, you can join 3D solids by using the UNION command to create a new 3D solid. You can also subtract volume from a 3D solid by using another intersecting 3D solid to determine what should be removed with the SUBTRACT command. The INTERSECT command can be used to calculate a new 3D solid based on the intersecting of two or more 3D solids. See Figure 22-14 for examples. You can find these three commands on the Boolean panel of the Solid tab.

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512 Part V: On a 3D Spree

Figure 22-14: Solid primitives on the left, and the result from UNION,

SUBTRACT, and INTERSECT commands.

Filleting and chamfering

Because fillets and chamfers are common real-world features, it’s logical that tools for creating them are available. You can fillet or bevel the edges of a 3D solid by clicking the Fillet Edge (or Chamfer Edge) split button on the Solid tab’s Solid Editing panel.

Both commands allow you to select multiple edges to fillet or bevel. When you select an edge, AutoCAD gives you feedback on how the selected edge will be affected. Figure 22-15 shows an L-shaped 3D solid that’s been filleted and chamfered.

Figure 22-15: Before and after filleting and chamfering a 3D solid.

You can remove a fillet or chamfer by starting the ERASE command and, at the Select Objects prompt, holding down the Ctrl key and selecting the fillet or chamfer to be removed. For fillets, you may need to also remove nearby filleted corners that might have been created during the application of the fillet.

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The FILLETEDGE and CHAMFEREDGE commands were new in AutoCAD 2011. You can still use the FILLET and CHAMFER commands on 3D solids, but the new commands are much more efficient.

Slice

The SLICE command allows you to cut a 3D solid along a plane. You can slice a 3D solid by using a planar curve such as a circle, 2D polyline, or a surface, among many others. When you slice a 3D solid, you can choose which part of the 3D solid is kept — or you can keep both. Figure 22-16 shows a solid model that’s been sliced in half. To start the SLICE command, choose Slice from the Solid Editing panel of the Solid tab. After the command is started, specify a 3D solid to slice, an axis or object to define the cutting plane, and then finally which new 3D solids to keep.

Figure 22-16: Carving up a solid model with the SLICE command.

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23

On a Render Bender

In This Chapter

Creating 2D working drawings from 3D models

Visualizing a 3D model

Lighting your models

Applying materials

Assigning a background

Applying render presets to a 3D model

The word design has the same Latin origin as designate, meaning to point out to or to show to others. If you have an idea and produce it yourself,

you aren’t a designer: You’re an artist or a craftsman (not that there’s anything wrong with that). You aren’t a designer until you tell some-

one else about your idea so they can do all the dirty, heavy work of producing it.

2D orthographic drawings go back to Roman times, but only in the past few years have we seen a significant change in how things are designed and how the designers communicate that vision to others. No, we don’t mean 2D CAD on a computer because that’s just a more efficient way of producing Roman-style drawings. The world we live in is 3D, but paper is 2D. Orthographic engineering drawings were developed for the sole purpose of getting the designer’s 3D idea transferred to a 2D format. The recipient of the drawing then transfers the idea back into 3D, first as an image in the mind and then as the physical object.

The big change coming is that low-cost computers are getting power-

ful enough, and software is getting sophisticated enough, that designers can now work in 3D on a personal computer. At the same time, 3D printers exist

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