The default method for drawing an ellipse is to specify the endpoints of one axis of the ellipse and then specify a distance representing half the length of the second axis. The endpoints of the first axis determine the orientation of the ellipse. The longer axis of the ellipse is called the major axis, and the shorter one is the minor axis. The order in which you define the axes does not matter. The program determines the major and minor axes based on their relative lengths. Half the major axis is called the major radius, half the minor axis is the minor radius. The ratio (minor radius divided by the major radius) defines the eccentricity of the ellipse. A circle is an ellipse with an eccentricity of 1.
Other methods to draw ellipses can be found in the Ellipse submenu of the Draw menu and in the Ellipses toolbar.
The Polyline Ellipse (PELLIPSE) settings variable: controls whether real ellipses or a polyline representation is created.
If the variable is ON, the Ellipse tool creates a closed polyline, if the variable is OFF real ellipses are created.
The difference between a real ellipse and a polyline representation of an ellipse is visible when you select the ellipse. A real ellipse has five handles: center point and the endpoints of the axes. A polyline representation of an ellipse is a closed polyline composed of arc segments.
real ellipse (left) and the polyline representation of an ellipse (right)
Note: Since ellipses cannot be used as a clip boundary for external references or to create clipped paperspace viewports, you must use a polyline representation to do these jobs.
Setting the Polyline Ellipse (PELLIPSE) system variable
Do one of the following:
- In the command bar type pellipse, then press Enter.
- In the Settings dialog, go to Drawing > Drafting > Entity Creation > Other entities .
General procedure to draw an ellipse
- Do one of the following.
- Click the Ellipse tool button () on the Draw toolbar.
- Type ellipse in the command bar, then press Enter.
- Type EL in the command bar, then press Enter.
You are prompted: Arc/Center/<First end of ellipse axis>:
A prompt menu displays:
- Specify the the first end of the ellipse axis.
You are prompted: Second end of axis:
- Specify the second end of the ellipse axis.
You are prompted: Rotations/<Other axis>:
A prompt menu displays:
- Specify the length of half the other axis of the ellipse.
Note: If the Polyline Ellipse variable is off, the Arc option is not available.
Editing an ellipse
- Select the ellipse.
The properties of the ellipse display in the Properties bar.
- Type a new value in the Center, Major radius, Minor radius, Radius ratio, Start angle or End angle field, then press Enter.
- Press the Esc key to stop editing the ellipse.