Learn/Drafting/2D Sketch Editor
Entity Types
At a glance
- Line — straight segment defined by start and end points
- Arc — circular arc by center, radius, start angle, and end angle
- Circle — full circle by center and radius
- Polyline — multi-vertex entity with straight or bulge-encoded arc segments; native DXF format
- Spline — B-spline (degree 1–5) with control points and knot vector; supports interpolation through points
Everything in a sketch is one of a handful of primitive entity types. There are no compound "rectangle" or "slot" objects — those tools commit plain lines and arcs, so every edge of every shape is individually selectable, trimmable, and dimensionable. Sketches also carry two utility types: points for construction reference and canvas entities (embedded images for tracing).
The primitives
- Line — start and end point.
- Arc — center, radius, start angle, end angle.
- Circle — center and radius. Circles are real solver entities, so diameter, concentric, equal-radius, and tangent constraints drive them directly.
- Polyline — a chain of vertices where each segment is straight or an arc, encoded as a DXF bulge value. Imported DXF and SVG geometry usually arrives as polylines.
- Spline — a B-spline defined by control points, knots, and weights, read directly from DXF SPLINE entities (cubic if the file doesn't say otherwise).
Arcs stay arcs
Polyline arcs use the standard AutoCAD bulge convention — bulge = tan(sweep / 4), positive for
counterclockwise — and that arc data is preserved through the entire pipeline. Nothing linearizes
an arc into little line segments until the CAM post-processor absolutely has to, which is why
profiles cut from sketches keep true G2/G3 arc moves in G-code instead of faceted approximations.
Every entity also carries display metadata — color, line style, and a layer name — covered in Entity Styling.