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ellipses
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Draw exact ellipses and elliptical arcs from a center and two axis points.
Ellipses are first-class construction objects in Locus, right alongside circles and arcs. You build them from three points, they render exactly, and they stay fully live - retarget any of the defining points and the ellipse reshapes.
An ellipse is defined by three points: a center, a point on the major axis (which sets the long radius and the tilt), and a minor-axis point (whose distance from the major axis sets the short radius). Click those three in turn and Locus draws the filled ellipse.
All three points remain editable and retargetable, so the ellipse is never "baked" - drag the center to move it, drag the major-axis point to lengthen or rotate it, drag the minor point to fatten or flatten it.
An elliptical arc is an open slice of an ellipse. It starts from the same three shape points - center, major, minor - and then takes a start point and an end point on the ellipse. Click the three shape points, then a start point, then wind the cursor to sweep the arc the short or long way around, and click to commit. It mirrors the circular Arc tool exactly.
A closed ellipse is a first-class fillable object, just like a circle: select it and use the Region tool, or click inside it with the Fill tool, and Locus fills the curve in place - no region loop required. The fill shows in the Layers style strip and exports to SVG. See Filling a circle or ellipse.
Ellipses draw as true ellipses on screen, not as chains of tiny straight edges. Crossings are exact too: where a line, ray, or segment meets an ellipse or elliptical arc, Locus computes the precise intersection points, and the arc's sweep is respected - a crossing outside the drawn arc correctly doesn't bind.
Caution
Confirm against the build A couple of boundaries to keep in mind. Where an ellipse meets a circle, arc, or another ellipse, the crossing is solved to very high precision but by a numerical method rather than a closed form. And ellipses aren't yet part of the flood-fill arrangement, so you can't flood-fill a region against an ellipse boundary. Confirm these against your version if a design leans on them.
< Previous: Circles & arcs | Next: Compass & straightedge >
- In the node graph: Ellipse | Elliptical Arc - build the same ellipses as nodes.