> For the complete documentation index, see [llms.txt](https://docs.openbrim.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.openbrim.org/templates/cadd/ellipse-cadd.md).

# Ellipse

An **Ellipse** is defined by a center point and two radii (semi-major and semi-minor axes). In bridge drawings it's a less common primitive than Circle or Rectangle but useful for elliptical foundation outlines, eccentric pad layouts, drainage pickup boundaries, and aesthetically curved features.

## Geometry

**Name:** Identifier within the parent CAD document. Must be unique.

**Level:** The layer controlling color, line weight, and dash style.

**Center X / Center Y:** Coordinates of the ellipse's center.

**Radius 1:** Semi-major axis length — the longer of the two radii.

**Radius 2:** Semi-minor axis length — the shorter of the two radii.

**Rotation:** Rotation about the ellipse's center. By default, Radius 1 is horizontal; rotate to align the major axis with a different direction.

## Editing

**Move:** drag the center handle to translate.

**Resize:** drag the four axis-end handles to change Radius 1 or Radius 2 independently. The center stays fixed.

**Rotate:** drag the rotation handle to align the major axis with the desired direction.

## Notes

For a true circle (Radius 1 = Radius 2), use a Circle — circles take a single radius and have purpose-built quadrant snap points that ellipses don't expose in the same way.

When the parent CAD document is alignment-driven, the ellipse's center is placed onto the alignment, but the ellipse itself stays a true ellipse (it does not warp further over horizontal curves).


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