688 Part IV Drawing in Three Dimensions

STEPS: Shading a Drawing

1.Open ab22-b.dwg from the CD-ROM.

2.Save it as ab22-02.dwg in your AutoCAD Bible folder.

3.Choose Tools Options and choose the System tab.

4.In Current 3D Graphics Display, choose your graphics system (it’s probably already selected) and click Properties.

5.Check Render Options and then click Enable Materials. (If you’re not using the default Heidi graphics display system, your options may be different.)

6.Click Apply & Close. Click OK to close the Options dialog box.

7.Choose View Shade Flat Shaded. This model has a brass-like material attached to it.

8.Choose View Shade Gouraud Shaded.

9.Choose View Shade Gouraud Shaded, Edges On.

10.Save your drawing. It should look like Figure 22-20.

Figure 22-20: The model shaded with the Gouraud

Shaded, Edges On option.

Using 3D Orbit

Because you cannot use other commands while in 3D orbit, you access the 3D orbit options by right-clicking in the drawing area to display the 3D orbit shortcut menu. You might find the 3D orbit toolbar helpful when working with 3D orbit. The toolbar contains many of the options that are available on the 3D orbit shortcut menu. Right-click any toolbar and choose 3D orbit to display the toolbar.

3D orbit enables you to view a 3D model by freely changing your view in real-time. Using 3D orbit is like orbiting the earth to view any continent or ocean below. When you enter 3D orbit mode, you cannot use other commands. In this regard, 3D orbit is like Realtime Pan and Realtime Zoom. Similarly, you can press Esc or Enter to exit 3D orbit mode.

Chapter 22 Viewing 3D Drawings 689

Tip 3D orbit can be used as a substitute for DVIEW, which is covered later in this chapter.

690 Part IV Drawing in Three Dimensions

Figure 22-22: Using the circular arrow cursor to rotate your model around an axis.

Rotating freely with the sphere and lines cursor

As soon as you move your cursor within the arcball, it takes a shape called “a small sphere encircled by two lines.” As you click and drag within the arcball, your model

moves around the center of the arcball in the direction that you drag. Imagine that your model is encased in a transparent sphere, similar to a gerbil or hamster ball. As you drag the cursor, you’re rotating the sphere around its center point. If you drag from one edge of the arcball to its opposite edge, you can release the mouse, move back to your starting point, and then click and drag again in the same direction. When you do this a few times, you rotate your model 360 degrees. You achieve the best results by dragging in a line in any direction, rather than ’round and ’round. Figure 22-23 shows a model rotated using the sphere and lines cursor. For each pane of the figure, the cursor is dragged from just inside the right arcball circle to just inside the left arcball circle (that is, horizontally).

Chapter 22 Viewing 3D Drawings 691

Figure 22-23: Using the sphere and lines cursor to rotate your model around its center.

Rotating around the vertical axis with the horizontal ellipse cursor

When you move your cursor over either the left or right quadrant circle on the arcball, it becomes a horizontal ellipse. As you click and drag from either quadrant, your model rotates around the arcball’s vertical axis, which extends from the top quadrant to the bottom

quadrant. Although your cursor enters the arcball, it retains its horizontal ellipse form until you release the mouse button. You can drag from one quadrant to its opposite quadrant, release the mouse button, move back to your starting point, and then click and drag again in the same direction. When you do this a few times, you rotate your model 360 degrees. Figure 22-24 shows a model rotated using the horizontal ellipse cursor.

692 Part IV Drawing in Three Dimensions

Figure 22-24: Using the horizontal ellipse cursor to rotate your model around the arcball’s vertical axis.

Rotating around the horizontal axis with the vertical ellipse cursor

When you move your cursor over either the top or bottom quadrant circle on the arcball, it becomes a vertical ellipse. As you click and drag from either quadrant, your

model rotates around the arcball’s horizontal axis, which extends from the left quadrant to the right quadrant. You can drag from one quadrant to its opposite quadrant, release the mouse button, move back to your starting point, and then click and drag again in the same direction. When you do this a few times, you rotate your model 360 degrees. Figure 22-25 shows a model rotated using the vertical ellipse cursor.

Chapter 22 Viewing 3D Drawings 693

Figure 22-25: Using the vertical ellipse cursor to rotate your model around the arcball’s horizontal axis.

Using the 3D orbit visual aids

3D orbit includes three visual aids that can help you find your bearings:

Compass: Displays a sphere within the arcball that is made up of three dashed lines labeled as the X, Y, and Z axes. The lines make your arcball look like a baseball. To display the compass, right-click and choose Visual Aids Compass from the shortcut menu.

Grid: Displays a grid of lines representing the XY plane. The Z coordinate of the grid is equal to the value of the ELEVATION system variable, which is set to 0 (zero) by default. Up to ten horizontal and vertical lines are drawn between the major lines, whose distance from each other is equal to the value of the GRIDUNIT system variable. You can set this value by choosing Tools Drafting Settings before you use this visual aid.

3D UCS icon: Displays a shaded, three-dimensional 3D UCS icon. The X axis is red, the Y axis is green, and the Z axis is blue.

694 Part IV Drawing in Three Dimensions

Figure 22-26 shows one model with the grid, and another with the compass. Both display the 3D UCS icon. You would rarely want to use all three. The compass and grid can both interfere with viewing your model and should be used temporarily when needed.

1.With 3D orbit mode active, right-click and choose More Continuous Orbit.

2.Click and drag in the direction of rotation that you want to create.

3.Release your mouse button. Your model continues to rotate in the same direction. All you do is watch.

Continuous orbit is an ideal way to view your model. As your model rotates, you can pick out any errors and then stop continuous orbit to fix them. You can change the direction of your continuous orbit at any time by clicking and dragging in a new direction and then releasing the mouse button.

To stop continuous orbit, choose Pan, Zoom, or Orbit from the shortcut menu. Zoom Previous exits 3D orbit and restores the view to the way it was before the orbit began.

Resetting the view

You can end up with some strange views of your model when using 3D orbit. With that in mind, AutoCAD provides a way to reset your view to the view that was current when you first started 3D orbit. With 3D orbit active, right-click and choose Reset View from the shortcut menu.

Chapter 22 Viewing 3D Drawings 695

Refining your 3D orbit view

3D orbit offers many options for refining your view so that you see just the view that you want. You can pan and zoom, adjust the camera distance, change the camera and target locations, create parallel and perspective views, set clipping planes, use a preset view, use shading options, and use materials that you’ve attached to objects. (See Chapter 25 for more about materials.)

Because you cannot use other commands while in 3D orbit mode, you must access most of these options by right-clicking in the drawing area to access the 3D orbit shortcut menu. You can also use the 3D orbit toolbar for some of these options.

Panning in 3D orbit

To pan in 3D orbit mode, right-click and choose Pan from the 3D orbit shortcut menu. You see the familiar hand cursor. Click and drag to pan, in the same way that you normally pan in realtime. To stop panning, right-click and choose Orbit or Zoom from the shortcut menu.

You can pan with visual aids, shading modes, and projection options active.

Zooming in 3D orbit

To zoom in 3D orbit, right-click and choose Zoom from the 3D orbit shortcut menu. You see the familiar magnifying glass cursor with a plus (+) and a minus (–) sign. Click and drag in the direction of the plus sign (toward the top of your screen) to zoom in; click and drag in the direction of the minus sign (toward the bottom of your screen) to zoom out, just as you do when you normally use zoom real-time. To stop zooming, right-click and choose Orbit or

Pan from the shortcut menu. You can zoom with visual aids, shading modes, and projection options active.

Zooming to a window and to extents in 3D orbit

To zoom to a window in 3D orbit, right-click and choose More Zoom Window from the shortcut menu. Your cursor displays a small rectangle. Click and drag, and then release the mouse button to define the two corners of the window.

To zoom to drawing extents in 3D orbit, right-click and choose More Zoom Extents from the shortcut menu.

Keeping the Z axis orientation steady

Controlling the orbiting with 3D orbit can be difficult. You may find that as you drag horizontally in the arcball, your model tumbles upside down. The Orbit Maintains Z option keeps the Z axis in its current direction when you drag horizontally within the arcball or horizontally from the left or right ellipse of the arcball. Use this option to prevent your object from rolling around. The idea is that you don’t want to see certain objects, such as houses, upside down.

To turn on this feature, right-click in 3D orbit and choose More Orbit Maintains Z. Repeat the process to toggle the feature off. AutoCAD saves this setting in your user profile so that it carries over to other drawings.

Adjusting the camera distance

You can adjust the distance between the viewer, called the camera, and the target, which by default is set to the center of the 3D view (this view may be different from the center of your model). Changing this camera distance is equivalent to zooming in and out.

696 Part IV Drawing in Three Dimensions

To adjust the camera distance in 3D orbit, right-click and choose More Adjust Distance from the shortcut menu. The cursor changes to a horizontal line with a double-headed arrow pointing up and down. Click and drag toward the top of your screen to move the camera closer to your objects — similar to zooming in. Click and drag toward the bottom of your screen to move the camera away from your objects — similar to zooming out.

Controlling view width and height

When you use 3D orbit, the Properties palette displays special properties that relate to 3D orbit features.

View Height is a way to specify the distance of the imaginary camera. In other words, you can use this property to zoom in and out on your model. A larger number makes your model look smaller because the distance (or height) of the camera from the model increases.

View Width is another way to zoom in and out. Here you specify the width of the view of the imaginary camera. A larger number makes your model look smaller because the view encompasses a larger area (and your model is a smaller part of that area).

To change these properties, click their row in the Properties palette. Type a new value and press Enter.

Creating parallel and perspective views

By default, 3D orbit (and all three-dimensional viewpoints) displays a parallel view. In a parallel view, parallel lines never converge. The value of a parallel view is that the shapes in your drawing do not appear distorted as you zoom in. In a perspective view, parallel lines converge. You may have had an assignment in art class (long ago) to draw railroad tracks that converge to give the impression of distance. Perspective view is more realistic because railroad tracks really do seem to converge in the distance. However, when you zoom in, these objects appear distorted. Use a perspective view when you want to convey a realistic sense of depth. In general, perspective view is most useful in architectural settings.

To create a perspective view in 3D orbit, right-click and choose Projection Perspective. To return to parallel view, choose Projection Parallel. For more information on perspective views, see the section “Defining a Perspective View” later in this chapter.

Chapter 22 Viewing 3D Drawings 697

Using a preset view

After you use 3D orbit a few times, your model may appear askew, with no indication of how to return it to a viewpoint that you can comprehend. You can switch to any of the preset views discussed at the beginning of this chapter. From 3D orbit, right-click and choose Preset Views from the shortcut menu. Then choose one of the standard viewpoints on the submenu list.

Setting clipping planes

You can create two invisible planes, a front clipping plane and a back clipping plane, that block your view of any objects outside the planes. Setting clipping planes is a good way to discard objects that you don’t want to see because they’re too close or too far away. For example, you might have a 3D house with trees in the background and a street sign in the foreground. Using clipping planes, you can block out the view of the trees and the street sign, and view only the house.

The Adjust Clipping Planes window enables you to visually move the front and back clipping planes in real-time and immediately see the results.

Because the clipping planes are parallel to your screen, you need to start by creating a view that is straight enough so that your clipping planes will cut across your model at the desired angle. I suggest using one of the preset views, as I just previously explained. For example, if you’re looking at a house and want to clip off the front and back porches, use the Front preset view to view your house from the front. You will then be able to create the desired front and back clipping planes. After you set your view, follow these steps:

1.From 3D orbit, right-click and choose More Adjust Clipping Planes. AutoCAD displays the Adjust Clipping Planes window, shown in Figure 22-27.

2.In the Adjust Clipping Planes window, you can do the following:

•Adjust Front Clipping: Click this button on the toolbar to move the front

clipping plane. Use the Adjust Clipping Planes cursor to click and drag the line that represents the front clipping plane.

•Adjust Back Clipping: Click this button on the toolbar to move the back clipping plane. Use the Adjust Clipping Planes cursor to click and drag the

line that represents the back clipping plane.

•Create Slice: After you adjust both the front and back clipping planes, use this button to move both clipping planes together, either up or down. Their

distance from each other remains constant.

• Pan: Click to pan the view inside the Adjust Clipping Planes window.

• Zoom: Click to zoom the view inside the Adjust Clipping Planes window.

•Front Clipping On/Off: Click this button to toggle the front clipping plane on or off.

•Back Clipping On/Off: Click this button to toggle the back clipping plane on or off.

698 Part IV Drawing in Three Dimensions

Back clipping plane

Adjust Clipping Planes toolbar Front clipping plane

Figure 22-27: The Adjust Clipping Planes window, shown with the model on the drawing area.

3.If you can’t see the back clipping plane, click Adjust Back Clipping and continue to drag down until the line representing the back clipping plane appears. If you can’t see the front clipping plane, click Adjust Front Clipping and continue to drag up until the line representing the front clipping plane appears.

4.After you set the clipping planes to your satisfaction, click the window’s Close box. You can now rotate you model in any direction; 3D orbit continually hides any portion of the model outside the clipping planes. However, as you rotate your model, the parts of the model outside the clipping planes change so that you see different portions of the model.

To turn off either or both clipping planes, right-click and choose More Front Clipping On or More Back Clipping On. Both of these items show a check mark when their clipping plane is on. Choosing the item again turns the clipping plane off.

Figure 22-28 shows how the house shown in Figure 22-27 looks after setting clipping planes and changing the rotation slightly. The front and back walls have been clipped off.

Chapter 22 Viewing 3D Drawings 699

Figure 22-28: A house after setting clipping planes and using the Hide shading option.

Using shading options

While in 3D orbit, you can use the shading options explained earlier in this chapter. To choose a shading option, right-click in 3D orbit, choose Shading Modes, and then choose one of the options from the shortcut submenu. These shading modes persist after you exit 3D orbit. To remove a shading mode from 3D orbit, right-click and choose Shading Modes Wireframe. You can also remove a shading mode after leaving 3D orbit mode by choosing View Shade, as explained earlier.

STEPS: Working in 3D Orbit

1.Open ab22-c.dwg from the CD-ROM. This is a 3D chair shown from a Northwest isometric view.

2.Choose View 3D Orbit. AutoCAD displays the arcball.

3.Place the mouse cursor outside the arcball so that you see the circular arrow cursor. Click and drag the cursor 360 degrees around the outside of the arcball so that the chair ends up in its original position.

4.Place the cursor inside the right small circle on the arcball so that you see the horizontal ellipse cursor. Click and drag the cursor to the left small circle. Release the mouse button. Again, click and drag the cursor from the right circle to the left circle so that the chair is approximately in its original position.