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21.Start the ARC command. The start point should be at the left quadrant of the left circle you just drew. The second point is the intersection of the vertical centerline and the top horizontal centerline. (There is an Endpoint object snap there.) The endpoint is the right quadrant of the right circle.

22.Choose Tools New UCS World. Choose View 3D Views SE Isometric. Then type hide to see the final result.

23.Save your drawing. The chair should look like Figure 21-19.

Figure 21-19: The completed glass-bottomed chair.

Summary

This chapter introduced you to 3D drawing. You read about:

Understanding all the types of 3D coordinates and how to use them

Using editing commands in 3D

Using point filters, object snaps, and grips in 3D drawings

Utilizing elevation and thickness

Understanding the HIDE command and the system variables that affect the hidden display

Working with User Coordinate Systems in 3D

In the next chapter, I explain all the ways to view 3D drawings.

Viewing 3D

Drawings

As soon as you start to work in three dimensions, you need to be able to see the drawing from different angles. By combining vari-

ous User Coordinate Systems (UCSs) and different viewpoints, you can draw any object in 3D.

Your basic point of reference is plan view in the World Coordinate System (WCS). This is the way you draw in 2D, so it’s familiar. Plan view is the view from the top. For a building, the top is obvious. However, for a bushing, which view is the top? Figure 22-1 shows a 2D drawing of a bushing. Figure 22-2 shows the 3D version. The left view of Figure 22-1 is the plan view looking down from the top. (Although your drawing calls this the plan view, engineering practice might call this the front view.)

When working in 3D, you can use many of the familiar 2D techniques for viewing your drawing:

Use ZOOM Previous to display the previous viewpoint.

Save views so that you can easily return to them.

Use real-time zoom and pan as well as all the other zoom options.

Create tiled viewports to display more than one view at a time.

22C H A P T E R

In This Chapter

Using the standard viewpoints

Using the DDVPOINT and VPOINT commands

Getting a plan view with the PLAN command

Shading your drawing

Using 3D orbit

Creating a perspective view

Laying out a 3D drawing

618 Part IV Drawing in Three Dimensions

Figure 22-1: The left image is the plan view, looking down from the top.

Thanks to Robert Mack, the Dexter Company, Fairfield, Iowa, for this drawing.

Figure 22-2: A 3D view of the bushing after using the HIDE command.

Working with the Standard Viewpoints

The View toolbar offers ten standard viewpoints. (Right-click any toolbar and choose View to display the View toolbar.) These viewpoints are useful — and easy to use —

because they’re the most commonly used viewpoints. You can do a lot of your work just using these viewpoints. The standard viewpoints show viewpoints relative only to the WCS, not the current UCS. Therefore, they’re most useful when you’re using the WCS.

To use a preset viewpoint, you can choose it from the View toolbar. You can also choose View 3D Views and choose the viewpoint you want from the submenu. Each of the preset viewpoints automatically does a Zoom Extents.

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Using the VPOINT command

The VPOINT command was the original, command-line method of setting viewpoints. Now it’s generally used for scripts and AutoLISP routines when you need a way to set a viewpoint from the command line. (AutoCAD LT does not support AutoLISP routines.)

The VPOINT command defines a viewpoint using X, Y, and Z vectors. The vectors for the standard viewpoints are based on a maximum of 1 unit. Imagine a model of the three axes floating out in space. You’re Superman and can fly around the model from any angle. When you’re over the Z axis, you can define the Z vector from 0,0,0 to your position as 1. The other vectors are 0 (zero) because you’re right over them, so that 0,0,1 defines the top, or plan, view. The next section shows the vector equivalents for the standard viewpoints, to give you a feel for the vector system.

The VPOINT command also has a Rotate option that is the command-line equivalent of the DDVPOINT command’s Viewpoint Presets dialog box. Using this option, you define a viewpoint by the angle from the X axis in the XY plane and then the angle from the XY plane.

	Looking at a drawing from the standard viewpoints
	Showing the viewpoints is easier than describing them. Here I show a simple 3D house from
	all ten standard viewpoints.
Note	A system variable, UCSORTHO, automatically changes the UCS to match the viewpoint when
	you switch to one of the orthographic (top, bottom, left, right, front, and back) viewpoints. In
	order to distinguish between the viewpoints and UCSs, I’ve turned UCSORTHO off for the fol-
	lowing section.
	Top view
	The top view is the plan view. You’re looking at the model from a bird’s-eye perspective,
	suspended over the model. The VPOINT equivalent is 0,0,1. Figure 22-3 shows a house
	from the top.

Figure 22-3: The top viewpoint of a 3D house.

620 Part IV Drawing in Three Dimensions

You can also get this view by typing PLAN on the command line. Note that the PLAN command does not change the UCS even though you choose to see the plan view of a different UCS. This actually makes it very flexible — you can see what your drawing looks like from a different UCS without actually changing the UCS. The PLAN command is explained later in this chapter.

Bottom view

The bottom view is the plan view for groundhogs. It’s not very useful for buildings, but it may be useful for 3D mechanical drawings. The VPOINT equivalent is 0,0,–1. Fig-

ure 22-4 shows the house from the bottom. Notice the direction of the UCS icon. Also, the square is missing on the icon, indicating you’re viewing from the negative Z direction, or from “underneath.”

Figure 22-4: The bottom viewpoint of the 3D house.

Left view

The left view shows you your model from the side — the left side, of course. In architecture it would be one of the elevation views. The VPOINT equivalent is –1,0,0. Figure 22-5

shows the house from the left view. Notice the backward text. The text was drawn from the right view.

Right view

The right view shows you your model from the right side. Like left view, right view is an elevation view. The VPOINT equivalent is 1,0,0. Figure 22-6 shows the house from the

right view. Notice that the text now appears correctly because it was drawn from this view.

Front view

The front view, another elevation view, shows your model from the front. The VPOINT equivalent is 0,–1,0. Figure 22-7 shows the house from the front. The text, stating that

the front faces the east, doesn’t represent any rule in AutoCAD or AutoCAD LT. It simply helps you see the differences in the sides of the house.

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Figure 22-5: The left view of the 3D house.

Figure 22-6: The right view of the 3D house.

Back view

The back view, another elevation view, shows your model from the back, as shown in Figure 22-8. Here you see the text of the front of the house, shown backward. The

VPOINT equivalent is 0,1,0.

SW isometric view

The SW (southwest) isometric view shows you your model from a diagonal viewpoint in all three dimensions (see Figure 22-9). Notice how one corner of the house is closest to you (the corner between the left and front views), and you’re also looking at the house from a

view halfway between a side view and the top view. The isometric views are excellent for viewing all the 3D objects in a drawing. As you can see, many more objects are visible than with the top view or any of the side views. The VPOINT equivalent is –1,–1,1.

622 Part IV Drawing in Three Dimensions

Figure 22-7: The front view of the 3D house.

Figure 22-8: The back view of the 3D house.

Figure 22-9: The SW isometric view of the 3D house.

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Don’t get confused with the house’s direction — the is front facing east. From your drawing’s point of view, east is 0 degrees when looking from the top view, and 0 degrees faces to the right.

SE isometric view

The SE (southeast) isometric view also shows your model from a diagonal viewpoint in all three dimensions. Here you’re looking at the house at the corner between the right

and front views, as well as halfway between a side view and the top view. You see the same objects as you do in SW isometric view. However, in a drawing not as symmetrical as the house, one view may bring certain objects to the front so that you can select them. The VPOINT equivalent is 1,–1,1. Figure 22-10 shows the house from the SE isometric view.

Figure 22-10: The SE isometric view of the 3D house.

NE isometric view

The NE isometric view shows your model from the corner between the right 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 22-11 shows the house from the NE isometric view.

Figure 22-11: The NE isometric view of the 3D house.