Ellipse

The ellipse command draws an ellipse using three clicks: a center point, the endpoint of the first (major) semi-axis at any angle, and the length of the second (minor) semi-axis. The two axes are always perpendicular to each other — the second axis direction is derived automatically from the first.

Drawing an ellipse

1. Type ellipse in the terminal or click the Ellipse toolbar button.
2. Click the center point, or type X,Y and press Enter for an exact coordinate.
3. Click the first axis endpoint — sets both the direction and the length of the first semi-axis. Coordinate entry works here too.
4. Set the second axis length — move the cursor perpendicular to the first axis, then click or type a length.

               ● ← first axis endpoint (step 3)
              /
  center ●  /  ← first axis (any angle)
            |
            ● ← cursor here sets second axis length (step 4)

The ellipse is placed after step 4 and the command exits.

Axis input — click, coordinate, or typed length

Center (step 2): click or type X,Y for an exact position.

First axis endpoint (step 3): click, or type X,Y for an exact coordinate. Angle locking also snaps to 45° increments — while locked, type a length and press Enter to place the endpoint at that exact distance.

Second axis (step 4): typed length is always available — no angle lock required. The direction is already fixed perpendicular to the first axis; typing sets only the length.

Key	Action
0–9, .	Append digit to the axis length (second axis phase)
Backspace	Delete the last typed character
Enter	Place the axis endpoint at the typed length

Coordinate entry (center and first axis endpoint)

1. Type the X value.
2. Press , — the terminal shows [X], [Y{cursor}].
3. Type the Y value.
4. Press Enter to confirm.

Keyboard reference

Key	Action
0–9, ., -	Start X coordinate entry (center/first-axis phases), or axis length when angle-locked
,	Lock X and move to Y entry
Backspace	Delete last typed character
Enter	Confirm typed coordinate or length
Escape	Cancel and reset

Grip editing — independent axis resizing

A selected ellipse exposes five grips:

Grip	Count	What it does
Center	1	Moves the whole ellipse; both axes unchanged
Major axis endpoints	2 (opposite ends of the longer axis)	Drag to resize the major semi-axis length; minor axis absolute size stays constant
Minor axis endpoints	2 (opposite ends of the shorter axis)	Drag to resize the minor semi-axis length; major axis unchanged

Major and minor axis grips are independent — you can reshape the ellipse without re-running the command.

Selecting ellipses

Method	Behaviour
Click	Selects if the click lands near the ellipse outline
Drag right (strict)	The axis-aligned bounding box of the ellipse must fit entirely inside the selection box
Drag left (crossing)	Any part of the ellipse outline that crosses the selection box boundary selects it

Supported edit commands

Command	What happens to the ellipse
Move	Translates the center; both axes unchanged
Copy	Creates an identical ellipse at a new center
Rotate	Rotates the center position and the major axis vector by the same angle
Mirror	Reflects the center and recalculates the major axis direction across the mirror axis
Scale	Scales the center position and multiplies both semi-axis lengths by the factor
Offset	Creates a concentric ellipse offset outward or inward by a fixed distance
Delete	Removes the ellipse

Properties

General

Property	Default	Meaning
Color	256 (ByLayer)	ACI color index
Layer	0	Layer assignment
Linetype	ByLayer	Named linetype pattern
Linetype Scale	1	Scale factor on the linetype pattern
Thickness	0	Extrusion thickness

Geometry

Property	Meaning
Center X / Center Y	Center of the ellipse
Major Axis X / Major Axis Y	Vector from center to the major axis endpoint (encodes both direction and length)
Axis Ratio	Ratio of minor semi-axis to major semi-axis (0 < ratio ≤ 1)
Start Angle / End Angle	Parametric angles in degrees; both are 0°/360° for a full ellipse

Ellipse vs Circle — when to use which

	Ellipse	Circle
Axes	Two independent semi-axes at any angle	One radius, symmetric
Rotation	Can be placed at any angle	No rotation
Typed input	Per-axis length	Radius only
Grip resize	Major and minor independently	All four cardinal points equally
Best for	Oblique views, oval features, perspective holes	Symmetric round features

DXF — ELLIPSE entity

Ellipses are saved as ELLIPSE entities in the DXF file. The format stores the center point, the full major axis vector (direction + length), and the axis ratio. Rotation, shape, and all style properties round-trip without loss. A circle is not stored as a degenerate ellipse — the two entity types remain distinct in the DXF model.