Graphics Programs Reference
In-Depth Information
The AutoCAD ELLIPSE command provides a straightforward way of drawing an ellipse:
You specify the two endpoints of one of its axes and then specify an endpoint on the
other axis. But like the ARC command, the ELLIPSE command offers a bunch of other op-
tions:
Arc:
Generates an elliptical arc, not a full ellipse. You define an elliptical arc just as
you do a full ellipse. The methods that I discuss in this section for creating an el-
lipse apply to either.
Center:
This option requires that you define the center of the ellipse and then the
endpoint of an axis. You can then either enter the distance of the other axis or spe-
cify that a rotation around the major axis defines the ellipse. If you choose the lat-
ter, you can enter (or drag the ellipse to) a specific rotation for the second axis
that, in turn, completely defines the ellipse.
Rotation:
With this option, you specify an angle which defines the curvature of the
ellipse — small angles make fat ellipses (0 degrees creates a circle, in fact), and
large angles make skinny ellipses. The name of the option, Rotation, has
something to do with rotating an imaginary circle around the first axis. If you can
figure out the imaginary circle business, you have a better imagination than I do.
The following command line example creates an ellipse by using the default end-
points of the axes method. Figure 9-3 shows an ellipse and an elliptical arc.
Command:
ELLIPSE
Specify axis endpoint of ellipse or [Arc/Center]:
pick or type the
first endpoint of one axis
Specify other endpoint of axis:
pick or type the other endpoint of
one axis
Specify distance to other axis or [Rotation]:
pick or type the end-
point of the other axis
You can create elliptical arcs (as opposed to the circular arcs that the
AutoCAD ARC command draws) by using the Arc option of the ELLIPSE command;
it's perfect for drawing those cannonball trajectories! Alternatively, you can draw
a full ellipse and use the TRIM or BREAK command to cut a piece out of it.
