Expand description
Recognizing the elementary shapes a NURBS curve or surface can be — a straight line, a circular arc, a plane, a surface of revolution — for whatever needs to know what an entity is, not just where it is: a reference axis built along an edge, a sketch placed on a face.
Every test is a question about the control net, answered with the kernel’s three-valued comparisons: a shape is recognized when the net could be exactly that shape — rounding can’t rule it out — and never because it is merely close to it. A curve that bends by a micron is not a line, however short.
The shapes themselves (Axis, Circle, Arc, Plane) carry
the few constructions everything built on them needs: projecting onto
them, intersecting them.
Structs§
- Arc
- A circular arc: the part of
circlefromstartcounter-clockwise (seen withcircle.normaltowards the viewer) toend— all of it whenstartandendcoincide. - Axis
- A straight line: through
point, along the unit vectordirection. - Circle
- A circle: around
center, in the plane normal to the unit vectornormal, ofradius. - Plane
- A plane: through
point, normal to the unit vectornormal.