AutoCAD & AutoCAD LT All-In-One Desk Reference For Dummies (2006)

302 Navigating a 3D Model

While one of the 3D orbit commands (or any of the other 3D navigation commands that we mention in the next section) is running, you can right-click and access the Navigation Modes menu (see Figure 3-6). This menu allows you to switch between Parallel and Perspective view, between different visual styles, or even to other navigation commands without having to exit one command in order to start another. You can also switch to a different navigation command by pressing the number next to it under the Other Navigation Modes submenu.

Figure 3-6:

The Navigation Modes menu.

If you hold down the Shift key first and then press and hold down the middle mouse button, you can temporarily switch to 3DORBIT. Pressing and holding the middle mouse button and then pressing the Shift key temporarily places you in orthogonal pan mode.

If the drawing contains a lot of objects, you can select a small set of the objects before starting one of the 3D orbit commands. This can help with performance in larger drawings because only the selected objects appear while the 3D orbit command is in use.

Navigating a 3D Model

AutoCAD offers other 3D navigation commands besides just the 3D orbit commands. Both zoom and pan are offered in 3D versions, but you can still use other zoom options such as window and extents. However, a few additional commands are used specifically for 3D navigation. These commands

304 Adding Some Color and Style to a 3D Model

Figure 3-7:

The 3D Navigation control panel of the Dashboard palette.

Adding Some Color and Style to a 3D Model

Looking at drawings that are displayed in 2D and 3D wireframe can make it rather difficult to visualize what is actually in there. AutoCAD and AutoCAD LT offer a few options to help you see what all of those lines actually mean. AutoCAD uses visual styles to display geometry so you only see the objects that are in front of others. AutoCAD LT doesn’t support visual styles but instead has a feature called shade modes. Shade modes were available in previous releases of AutoCAD to hide faces that are not those closest to the current viewpoint.

Visual styles in AutoCAD

Visual styles allow you to see your drawing in a hidden, shaded, or semirendered state. Visual styles are available from the Visual Styles Manager palette or the Visual Style control panel on the Dashboard palette. To display the Visual Style Manager palette (see Figure 3-8) from the menu bar, choose Tools Palettes Visual Styles. Double-click one of the available visual styles to set it current. You can also make a custom visual style and make changes to it by changing its properties at the bottom of the palette. You can set a visual style current when drawing to give you a sense of what lines you might want to snap to.

Visual styles are new in AutoCAD 2007, and they make it much easier to get different looks to a 3D model for presentation purposes.

The Visual Style control panel (see Figure 3-9) on the Dashboard palette contains a variety of controls that allow you to change to a different visual style, enable x-ray mode to see through faces, control how faces and edges are displayed, and even the display of shadows in a scene.

Adding Some Color and Style to a 3D Model 305

308 Working with Regions

Creating regions

Because regions are created from existing objects in a drawing, you first must create the closed objects or loops and then use the REGION command to generate a region out of them. A region is created for each closed object or loop that is selected. To start the REGION command, you can select Region from either the Draw menu on the menu bar or the Draw toolbar. An example of the REGION command follows, along with the objects that were selected (see Figure 4-1):

Command: _region

Select objects: Select the closed objects or loops

Specify opposite corner: 8 found Select objects: Press Enter

6 loops extracted.

6 Regions created.

Figure 4-1:

Closed objects converted to regions.

When you use the REGION command (and some of the other commands that are covered in this chapter), the original objects that you select to create the region or 3D object from are deleted automatically. To keep the original objects from being deleted, set the system variable DELOBJ to a value of 0.

Modifying regions

Regions are interesting objects because they are no longer 2D objects, nor are they 3D objects, so you modify them in a slightly different way. Although regions are not 3D objects, some of the 3D modify commands can be used on them. If you want to remove a portion of a region with another region, you wouldn’t use the TRIM command; instead, you would use the SUBTRACT command. You can use the EXPLODE command to convert a region back to 2D objects.

Union

Union allows you to combine two or more regions into a single region. This allows you to create very complex 2D objects that can later be extruded to create a 3D object. A great example of this is a metal plate that is used to

310 3D Polylines and Helixes

I:68.9979 along [0.9864 0.1644]

J:199.8441 along [-0.1644 0.9864]

Write analysis to a file? [Yes/No] <N>: Press Enter

3D Polylines and Helixes

Although a line object is not in one sense a 3D object, lines can have a different starting and ending z coordinate value, which makes it a 3D command. The 3DPOLY command allows you to draw 3D polylines, and the HELIX command allows you to create 2D and 3D spirals. These are not in one sense the same as a solid or a surface, but they can be created with varying different z coordinate values without the need to change the current user coordinate system (UCS). For more information on the UCS, see Book V, Chapter 2.

3D polyline

3D polylines are very similar to the 2D polylines that you are already familiar with, with the exception that they support only straight segments, and a different z coordinate value can be specified for the start and end point of a segment. You use the 3DPOLY command to create a 3D polyline, which can be started by choosing Draw 3D Polyline, or entering 3DPOLY at the command line or dynamic input tooltip.

Helix

Helixes can be used to create 2D and 3D spirals, shown in Figure 4-2, that might be used to represent springs, coils, or even door stops. To create a 2D helix, use a height value of 0. Use the HELIX command to create a helix. The HELIX command is started by selecting Helix from the Draw menu on the menu bar, or entering HELIX at the command line or dynamic input tooltip.

The HELIX command is new in AutoCAD 2007and is not supported in AutoCAD LT.

Figure 4-2:

Helixes can be used to create springs.