700 Part IV Drawing in Three Dimensions

5.Place the cursor inside the arcball so that you see the small sphere/two lines cursor. Click and drag the cursor around in several directions until you have a feel for how the movement of the cursor moves the chair. See if you can move the chair back to its original position.

6.Right-click and choose Shading Modes Hidden.

7.Right-click and choose More Continuous Orbit. Click and drag with the cursor, making a small movement from right to left, and then release the mouse button. You may need to try this a couple of times to find a continuous orbit that you like. Try clicking and dragging in a different direction to change the direction of the continuous orbit, and then release the mouse button.

8.Right-click and choose Orbit to stop the continuous orbit.

9.Right-click and choose Reset View to re-display the chair exactly in its original view.

10.Right-click and choose Pan. Pan the chair to the right a little.

11.Right-click and choose Zoom. Zoom the chair in slightly.

12.Right-click and choose Projection Perspective. You can see how the chair looks slightly distorted. Right-click and choose Projection Parallel.

13.Right-click and choose Preset Views NW Isometric.

14.Press Esc to exit 3D orbit mode.

Don’t save your drawing.

Using Tiled Viewports

As you learned in Chapter 8, you can create multiple viewports to view your drawing at different zooms and pans. Tiled viewports are very helpful in 3D drawings as well. Although you can, and should, save UCSs and views, if you find yourself switching back and forth between two to four viewpoints, try creating two to four viewports with the different viewpoints and UCSs in them. The only disadvantage is that you have less screen real estate for each viewpoint.

Defining a Perspective View

The original command for defining views with perspective from any angle and distance was DVIEW. The newer 3D orbit feature is easier to use than DVIEW, but you may still find DVIEW helpful for its precise ways of defining a view. (Also, 3D orbit is not available in AutoCAD LT, whereas DVIEW is.)

Like 3D orbit, DVIEW uses the metaphor of a camera. There is a camera point (where you are standing) and a target point (what you are looking at). By defining these two points, you can create either close-up or distance views, much as you would with the zoom or panoramic lens of a camera.

The DVIEW command creates both parallel and perspective views. Figure 22-29 shows a parallel view. Notice the side brackets. Figure 22-30 shows a perspective view of the same model. The side brackets appear to approach each other as they become more distant.

Chapter 22 Viewing 3D Drawings 701

Figure 22-29: A parallel view created with DVIEW.

Thanks to Robert Mack of the Dexter Company, Fairfield, Iowa, for this drawing, a base housing for an industrial washing machine.

Figure 22-30: A perspective view of the same model.

Using DVIEW

To create a perspective view, type dview on the command line. At the Select objects or <use DVIEWBLOCK>: prompt, select the objects that you want to include in the process of defining the perspective view.

You should select as few objects as you need to visualize the final result if you have a complex drawing. If you want to select the entire drawing, type all even if the current view doesn’t display the entire drawing.

Press Enter if you don’t want to choose any objects. The command substitutes a block called dviewblock, which is a simple house. You can use the house to set your perspective view.

702 Part IV Drawing in Three Dimensions

Understanding the DVIEW options

DVIEW comes with a bewildering array of options that you use to specify the angle and distance of the view. To use these options, start the DVIEW command and select the objects that you want to view, or press Enter. You see the following prompt:

Enter option [CAmera/TArget/Distance/POints/PAn/Zoom/TWist/CLip/Hide/Off/Undo]:

You use these options to define the perspective view, as explained in the following sections.

Camera

Use the Camera option to specify the angle of the camera, which represents where you’re standing. You need to specify the angle from the X axis in the XY plane and the angle from the XY plane. This is very similar to the way that you specify a view using the DDVPOINT command, explained earlier in this chapter.

When you choose this option, by right-clicking and choosing Camera, you see the following prompt:

Specify camera location, or enter angle from XY plane, or [Toggle (angle in)] <35.2644>:

The default angle is based on the current view when you start DVIEW. If you know the angle from the XY plane, you can just type it in. You can also move the cursor vertically to dynamically see the results. The view constantly changes as you move the cursor, moving up over your objects as you move the cursor up, and down as you move the cursor down. Move the cursor in one direction and then keep it still for a second to see the full effect.

However, moving the cursor horizontally changes the angle from the X axis in the XY plane. It can be confusing to change both angles at once, and so you can limit the effect of your cursor movement to one angle. You can do this with the Toggle suboption.

Right-click and choose Toggle (angle in) to see the next prompt of the Camera option:

Chapter 22 Viewing 3D Drawings 703

Target

The Target option (right-click and choose Target) works exactly like the Camera option, except that it defines the angles for the target of your viewpoint (what you would see through the camera lens). However, the angles are relative to the camera position. If you’ve already set the camera angles, then the target angles default to those angles that you create by drawing a straight line from the camera angle through 0,0,0. As with the Camera option, use the Toggle suboption to switch between the two angles that you need to specify.

Distance

The Distance option is very important because you use it to turn on Perspective mode. Before you use this option, the views that you see are parallel views. When you use the Distance option, you see a slider bar at the top of the screen, as shown in Figure 22-31. After you choose a distance, the Perspective mode icon replaces the UCS icon if your UCS display is set to 2D. (Choose View Display UCS Icon Properties.)

Figure 22-31: Using the Distance option turns on Perspective mode and displays a slider bar.

The command line displays the Specify new camera-target distance <3.0000>: prompt. You can type a distance from the camera to the target or use the slider bar. Move the cursor to the right to zoom out. Moving the cursor to 4x is equivalent to using the ZOOM command and typing 4x . Move the cursor to the left of 1x to zoom in. The zoom factor is relative to the current display, and so 1x leaves the zoom unchanged.

You can also type a distance in drawing units.

Points

You can use the Points option (right-click and choose Points) to define the camera and target. The command line displays the Specify target point <0.3776, -0.1618, 1.0088>: prompt. The default target point, which is different for each drawing, is the center of the current view. You see a rubber-band line from the target point, which you can use to find your bearings when choosing a new target point. You can also type a coordinate. At the Specify camera point <- 1.5628, 0.9420, 2.2787>: prompt, pick or type a point. You can use the rubber-band line stretching from the target so that you can visualize the camera and target points.

704 Part IV Drawing in Three Dimensions

Chapter 22 Viewing 3D Drawings 705

Figure 22-32: This model has a front clipping plane that hides the front of the model. Compare it to Figure 22-30.

When you choose the Clip option, you see the Enter clipping option [Back/Front/Off] <Off>: prompt. Specify Back or Front to set the back or front clipping planes. Specify Off to turn off all previously defined clipping planes.

Note When you use the Distance option to create a perspective view, the option automatically turns on a front clipping plane at the camera point.

When you specify the Front suboption, the command line responds with the Specify distance from target or [set to Eye(camera)/ON/OFF] <2.5682>: prompt. Specify Eye to set the clipping plane at the camera point. You can define the clipping plane by typing in a distance, or using the slider bar that appears at the top of your screen. As you move the cursor on the slider bar, stop to let the drawing redraw so that you can see the result.

When you specify the Back suboption, the command line displays the Specify distance from target or [ON/OFF] <-5.5826>: prompt. Specify On or Off to turn the clipping plane on or off, or specify the distance as for the front clipping plane.

Hide

The Hide option performs a hide, just like the HIDE command, thus letting you clearly see the results of the view that you’ve created.

Off

The Off option turns off Perspective mode and returns you to a parallel view. Otherwise, when you leave DVIEW after going into Perspective mode, your drawing retains the perspective view until you change the view — for example, with VPOINT. Until then, you cannot pick points on the screen or use object snaps, which can be very frustrating. This option enables you to exit from DVIEW in the normal viewing mode.

Undo

The Undo option undoes the effect of the last DVIEW option. You can undo through all of the changes that you have made in DVIEW.

706 Part IV Drawing in Three Dimensions

STEPS: Creating Perspective Views

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

2.Save it as ab22-03.dwg in your AutoCAD Bible folder. This is a portion of a 3D house in plan view, as shown in Figure 22-33. Make sure that OSNAP is on. Set a running object snap set for endpoint, and turn off any other object snaps.

3.You want to create a perspective view from approximately 1 to 2 in Figure 22-33. You can see right away that the wall near 1 will need clipping. To find the distance of the clipping plane from the target, choose Tools Inquiry Distance, and pick 3 and 4. The pertinent information is Distance = 12'-5 9/16". You may have a slightly different distance. To see the distance information, press F2 to open the Text window.

4.Choose View 3D Views NE Isometric. The result is as shown in Figure 22-34. This is a quick approximation and helps you to plan your camera and target points. To test for endpoints, start the LINE command. Place the cursor at 1 in Figure 22-34. The Endpoint SnapTip and marker appear. Place the cursor at 2, the top of the table leg. You should see the Endpoint SnapTip and marker. Press Esc to cancel the LINE command without drawing a line.

1

3

4

2

Figure 22-33: A 3D house in plan view.

Thanks to Andrew Wilcox of Virtual Homes, Inc., Hammonds Plains,

Nova Scotia, Canada, for this drawing.

5.Type dview . At the Select objects or <use DVIEWBLOCK>: prompt, type all . Press Enter to end object selection.

6.At the main DVIEW prompt, right-click and choose Points. At the Specify target point <14'-5 15/16", 21'-9 3/8", 6'-1 1/4">: prompt, pick the endpoint at 2 in Figure 22-34. At the Specify camera point <14'-6 15/16", 21'-10 3/8", 6'-2 1/4">: prompt, pick the endpoint at 1.

Chapter 22 Viewing 3D Drawings 707

2

1

3

4 5

Figure 22-34: The NE isometric view of the house.

7.Right-click and choose Distance. At the Specify new camera-target distance <20'- 10 15/16">: prompt, move the cursor to 4x on the slider bar. Take your hand off the mouse to let the drawing redraw until you can see the result. Pick at the 4x mark. Notice the perspective view icon.

8.To move the camera point, right-click and choose Camera. At the Specify camera

location, or enter angle from XY plane, or [Toggle (angle in)] <11.7252>: prompt, type 8 to lower the camera point slightly. At the Specify camera location, or enter angle in XY plane from X axis, or [Toggle (angle from)] <11.72523>: prompt, move the cursor close to 3 in Figure 22-34, relative to the screen, not the model, and click.

9.Right-click and choose Zoom. At the Specify lens length <35.000mm>: prompt, type 60 to zoom in slightly.

10.Right-click and choose Clip. Right-click and choose Front to set the front clipping plane.

At the Specify distance from target or [set to Eye(camera)] <83'-7 1/2">: prompt, type 13' . The front walls that are blocking the view disappear.

11.Right-click and choose Pan. At the Specify displacement base point: prompt, pick 4 in Figure 22-34, relative to the screen, not the drawing. At the Specify second point: prompt, pick 5 relative to the screen. The display moves down.

12.Right-click and choose Hide to hide the drawing. Your drawing should look approximately like Figure 22-35.

13.Press Enter to end the DVIEW command.

14.After all that work, you should save the view. Choose View Named Views. On

the Named Views tab, click New. In the New View dialog box, type Perspective 1 in the View Name text box. Click OK. Click OK to return to your drawing.

15.Save your drawing.