624 Part IV Drawing in Three Dimensions

NW isometric view

The NW isometric view shows your model from the corner between the left and the back views, as well as halfway between a side view and the top view. The VPOINT equiv-

alent is –1,1,1. Figure 22-12 shows the house from the NW isometric view.

Figure 22-12: The NW isometric view of the 3D house.

Using DDVPOINT

If the standard views aren’t sufficient for your needs, DDVPOINT can give you both flexibility and precision. To use this command, choose View 3D Views Viewpoint Presets to open the Viewpoint Presets dialog box, shown in Figure 22-13. This dialog box enables you to set the view to a great degree of accuracy.

Figure 22-13: The Viewpoint Presets dialog box.

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The left side of the dialog box determines the angle from the X axis in the XY plane. These angles work as follows:

270	Front view
0	Right view
90	Back view
180	Left view

	Other angles result in viewpoints between these views. For example, an angle of 315 degrees
	enables you to look at your drawing from a view between front and right. If you’re thinking
	that this is similar to the SE isometric view, you’re correct.
	The right side of the dialog box determines the angle from the XY plane, in the Z direction. A
	0-degree angle enables you to look at your drawing from the front, back, or one side (eleva-
	tion views) — depending on the setting on the left part of the dialog box. Often you want to
	look at your drawing from above. A 90-degree angle shows you the plan view. An angle between
	0 and 90 gives you a slanted view from the top — such as one of the isometric standard views.
	(Actually, the isometric views set the angle from the XY plane to 35.3 degrees.)
Tip	There’s an art to using the two dials to set the view angle that you want. If you click the
	inside border of either one, close to the indicator needle, you set the angle based on exactly
	where you clicked. This results in uneven degrees, such as 47.6. However, if you click the out-
	side border of either image, or the numbers themselves, the angle is rounded to the value in
	the segment.
	When you open the dialog box, the black needles indicate the angles for the current view. When
	you change the angles, the black (or white) needles move to the new angle but the original
	needle remains to indicate the current angle. This enables you to constantly see the current
	angles for reference.
	Beneath the dials are text boxes that reflect your choices. You can simply type the angles you
	want in the text boxes.
	A very handy Set to Plan View button is at the bottom of the dialog box. This enables you to
	quickly return to plan view when you get a little dizzy from flying around your model.
	You can set the viewing angles either based on the WCS or relative to a different UCS that
	you’re using. It can get confusing if you have several different UCSs and start viewing them
	from several different viewpoints. As a result, the default is to view the drawing based on the
	WCS. However, sometimes you need to see your drawing relative to a UCS you’ve created. To
	do so, click Relative to UCS.
Tip	Keep the number of UCSs to the minimum necessary and save them. When possible, use a
	new viewpoint instead of creating a new UCS.
	Click OK after you finish making your changes.

On the	The drawing used in the following Step-by-Step exercise on using standard viewpoints and
CD-ROM	DDVPOINT, ab22-a.dwg, is in the Drawings folder on the CD-ROM.

626 Part IV Drawing in Three Dimensions

STEP-BY-STEP: Using Standard Viewpoints and DDVPOINT

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

2.Save it as ab22-01.dwg in your AutoCAD Bible folder. It shows the same house used in the earlier figures in this chapter from the SE isometric view.

3.Type ucsortho 0 to turn off the UCSORTHO system variable. Turning off UCSORTHO prevents the UCS from changing whenever you switch to one of the six orthogonal viewpoints.

4.Right-click any toolbar and choose View to open the View toolbar. Choose Top View from the Viewpoint toolbar.

5.Choose Bottom View from the Viewpoint toolbar. Notice that the small circle at the intersection of the X and Y axes disappears.

6.Choose Front View from the Viewpoint toolbar. You see the front of the house with the two strange bushes.

7. Choose Right View from the Viewpoint toolbar. You see the text “North side.”

8.Choose NW Isometric View from the Viewpoint toolbar. You’re looking at the back of the house.

9.Choose SW Isometric View from the Viewpoint toolbar. You’re looking at the front of the house. If you want, try the rest of the standard viewpoints.

10.Choose View 3D Viewpoint Viewpoint Presets to open the Viewpoint Presets dialog box. Set the left dial (angle from X axis) to 315 degrees by clicking the number 315. Set the right dial (angle from XY plane) to 60 degrees by clicking the second from the top segment pointed to by the number 60. Click OK. You see a view somewhat like the SE isometric view, but from much higher up.

11.Repeat the DDVPOINT command. In the X Axis text box, type 240. In the XY Plane text box, type 5. Click OK. You get a view from slightly off the ground, much as you might see it if you were walking up to the house.

12.Type hide . Notice that you can see the windows on the far side through the windows on your side of the house.

13.Choose View Named Views on the Named Views tab and click New. In the New View dialog box, type the name of the view, walk up. Click OK. Click OK again to return to your drawing. It should look like Figure 22-14.

14.If you’re working on someone else’s computer or want UCSORTHO on, type ucsortho 1 to turn it back on.

15.Save the drawing.

Note You cannot save the display that you see when you use the HIDE command. When you restore the view, you see it as a wireframe display. You can, however, make a slide of the view. Chapter 30 covers slides. You can also use SHADEMODE to continue working with the hidden view. Choose View Shade Hidden.

Chapter 22 Viewing 3D Drawings 627

Figure 22-14: The final view of the house.

Working with the Tripod and Compass

You can choose another method of defining views, using the VPOINT command. To start this command, choose View 3D Views Viewpoint. The tripod and compass appear, as shown in Figure 22-15.

Figure 22-15: The VPOINT tripod and compass are used to define viewpoints in 3D.

If you type the VPOINT command, or press Enter to repeat the command, press Enter at the

Current view direction: VIEWDIR=-1.0000,-1.0000,1.0000 Specify a view point or [Rotate] <display compass and tripod>: prompt to see the compass and tripod. (The numbers show the current viewpoint.)

628 Part IV Drawing in Three Dimensions

Move the cursor about, and two things happen. The cursor moves within the compass, and the axes dynamically shift position.

Imagine that you take a tangerine and make a large cross-shaped cut at the very bottom. Then you open out the bottom and remove the peel from the tangerine. Flatten the peel on the table. This is the concept of the compass, except that the outer edge is round. (The tangerine peel would have the shape of the cuts on its outer edge.) The very center of the compass — or the peel — is like the North Pole. When you’re over the North Pole, you’re looking straight down at your model — or the tangerine. This produces a plan view. The inner circle of the compass is where the middle of the tangerine was — at the equator. From the equator, you’re looking sideways (from the front, back, or side) at your model. The outer circle of the compass represents the South Pole. From over the South Pole, you’re looking at the bottom of your model — or the tangerine.

All of this is equivalent to the right image in the Viewpoint Presets dialog box that you use with the DDVPOINT command — it determines your view relative to the XY plane:

At the center of the compass, you’re right on top, looking down. This is a plan view.

At the inner circle, you’re on the side, looking at the XY plane on its edge.

At the outer circle, you’re beneath the XY plane, looking up.

The cross that goes through the compass represents the X and Y axes. If you place the cursor on the positive (right) side of the X axis, you’re looking at the tangerine from its right side — this is equivalent to a right view. The position of the cursor relative to the X and Y axes is equivalent to the left image in the Viewpoint Presets dialog box that you use with the DDVPOINT command — it determines your view relative to the X axis in the XY plane. To summarize, going clockwise:

The positive X axis gives you a right view.

The negative Y axis is equivalent to a front view.

The negative X axis gives you a left view.

The positive Y axis gives you a back view.

When you have the cursor at the desired location, simply click. Your drawing displays the viewpoint you specified.

You cannot get an exact viewpoint this way. However, some people find this method of defining a viewpoint more intuitive. You can also look at the tripod as the axes move about. But be careful — sometimes it’s difficult to see if an axis is coming toward you or going away from you.

Along with the tripod and compass, you see the current UCS icon based on the current UCS to help you get your bearings. Figure 22-16 shows a cursor location that results in the viewpoint shown in Figure 22-17. This is very close to the SE isometric view.