How to Use the ELlipse Command in AutoCAD
The AutoCAD ELlipse command is easy to use. In case you’ve forgotten your ninth grade math, an ellipse is sort of a squished circle although it may be more accurate to say that a circle is an unsquished ellipse. Please excuse the technical jargon. Mathematically, an ellipse is defined by a major (long) axis and a minor (short) axis. These axes determine the ellipse’s length, width, and degree of curvature. An elliptical arc is an arc cut from an ellipse.
The AutoCAD ELlipse command provides a straightforward way to draw an ellipse: You specify the two endpoints of one of its axes and then specify an endpoint on the other axis. Like the Arc command, however, the ELlipse command offers several other options:
- Arc: Generates an elliptical arc, not a full ellipse. You define an elliptical arc just as you define a full ellipse.
- Center: Requires that you define the center of the ellipse and then the endpoint of an axis. You can then either enter the length of the other axis or specify that a rotation around the major axis defines the ellipse. If you choose the latter option, you can enter (or drag the ellipse to) a specific rotation angle for the second axis that, in turn, completely defines the ellipse.
- Rotation: Specifies an angle that defines the curvature of the ellipse — small angles create wide ellipses (0 degrees creates a circle, in fact), and large angles make thin ellipses. After dinner, when your plate is empty, hold it vertically to look at it straight on. It looks like a circle. Slowly rotate the plate about its vertical axis until you’re looking at it edge-on. Between these two views, you will see every possible ellipse as defined by the rotation angle — and your dinner guests will begin to wonder about you.
The following command line example creates an ellipse by using the default endpoints of the axes method. Enter ELlipse and press Enter or click the Ellipse button on the Ribbon:
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 endpoint of the other axis.
Here is an ellipse and an elliptical arc.
You can create elliptical arcs (as opposed to the circular arcs that the Arc command draws) by using the Arc option of the ELlipse command; it can draw a respectable representation of a snowball trajectory, neglecting air resistance. Alternatively, you can draw a full ellipse and use the TRim and BReak commands to cut a piece from it.