Graphics Programs Reference
In-Depth Information
it in perspective. You can switch from perspective to parallel projection by chan-
ging the PERSPECTIVE system variable's value from 1 to 0. Be very careful if you
do this, because you can't change it back again! You could use UNDO to reverse
the change, but if you save and close the drawing, you're sunk.
The six orthographic and four isometric views work well for showing 3D models of com-
mon objects such as mechanical components and buildings. (You can also change to
plan view,
which is a top-down view of either the world coordinate system or a user co-
ordinate system.)
AutoCAD LT has limited 3D viewing capabilities. The same preset views are in
both AutoCAD and AutoCAD LT, and there's also a Viewpoint Presets dialog box
(DDVPOINT command) in which you set a viewing position by specifying angles in
and from the XY plane. Finally, there's the really ugly command-line only VPOINT
command (Man, that one's soooo ugly it's not even on the Ribbon!).
Orbit à go-go
Preset views are fine for many 3D modeling tasks, but if you really want to have
fun, 3DOrbit (not in AutoCAD LT) is your ticket to it. (Orbiting a 3D model in AutoCAD is
similar in concept to orbiting around the Earth in a satellite — only a lot cheaper.) There
are two
orbiter
modes: Constrained and Free. Constrained mode is pretty much like the
Free mode with training wheels.
Free Orbit displays an
arcball
on the screen — a circle representing a sphere
around your object. You click various places inside, outside, and on the arcball and then
drag to change the 3D view. The idea is that you're spinning an imaginary sphere con-
taining your model. As you drag the cursor, AutoCAD updates the screen dynamically.
You can start Constrained orbiting, the 3DOrbit command, by holding the
SHIFT key down and then holding the middle mouse button while dragging the
mouse.
