An ellipse in AutoCAD is a geometric shape representing a closed, oval-shaped curve. It is a fundamental drawing entity used to depict elliptical forms in designs and technical drawings.
In AutoCAD, an ellipse is created using the ELLIPSE command, which can draw either a full ellipse or an elliptical arc. The creation process, as defined by the command's functionality, relies on specifying key points that determine the ellipse's size, shape, and orientation.
According to the command's definition:
- The first two points you specify define the location and the length of the first axis. This axis can be either the major or minor axis of the ellipse.
- The third point you specify determines the distance from the center of the ellipse to the end point of the second axis. This third point establishes the extent of the other axis perpendicular to the first one, thus defining the ellipse's overall shape (how "squashed" or "round" it is).
This method effectively allows users to control the orientation and dimensions of the ellipse precisely.
Creating an Ellipse in AutoCAD
The primary way to create an ellipse is through the ELLIPSE command (command alias EL). While the reference describes one method involving three points, the command offers different options:
Axis-End Method (Matches Reference Description)
This is the default method often used:
- First Point of Axis: Pick the start point of the first axis.
- Second Point of Axis: Pick the end point of the first axis. This defines its position and length.
- Distance to Other Axis Endpoint: Pick a point that defines the distance from the midpoint of the first axis (which is the ellipse's center) to the end of the second axis.
This process is concisely described in the command reference: "The first two points of the ellipse determine the location and length of the first axis. The third point determines the distance between the center of the ellipse and the end point of the second axis."
Center Method
This method involves first defining the center of the ellipse:
- Center Point: Pick the center of the ellipse.
- Endpoint of First Axis: Pick the end point of the first axis. This defines the direction and half-length of the first axis.
- Distance to Other Axis Endpoint: Pick a point that defines the distance from the center to the end of the second axis.
Elliptical Arc
The ELLIPSE command also includes an Arc option, allowing you to create only a portion of an ellipse. After defining the full ellipse using either the Axis-End or Center method, you are prompted to specify start and end angles (or points) to trim the ellipse into an arc.
Key Properties of an Ellipse in AutoCAD
When you create an ellipse in AutoCAD, it possesses several key properties that you can view and modify:
| Property | Description |
|---|---|
| Center | The midpoint of both the major and minor axes. |
| Major Axis | The longer axis passing through the center. |
| Minor Axis | The shorter axis passing through the center. |
| Axis Endpoint | Coordinates of the endpoints of the axes. |
| Start Angle | Starting angle for elliptical arcs (if applicable). |
| End Angle | Ending angle for elliptical arcs (if applicable). |
Understanding how the ELLIPSE command uses the specified points to define these properties is crucial for accurately drawing elliptical shapes in AutoCAD.
Practical Use
Ellipses are commonly used in technical drawing for:
- Representing holes viewed at an angle.
- Drawing cylindrical or circular objects in isometric or oblique projections.
- Creating decorative shapes or architectural elements.
- Defining boundaries or outlines that are not perfectly circular.
Mastering the ELLIPSE command and its various creation methods is essential for drafting accurate and complex designs in AutoCAD.
