marching algorithm for surface intersection
surfaces of revolution (lathed)
fix surface-line intersection
cylinder-line and plane-line special cases
exact boundaries when near pwl trim
step and repeat rotate/translate
short pwl edge avoidance
faces
take consistent pwl with coincident faces
exact curve export (at least for dxf)
hidden line removal from mesh
line styles (color, thickness)

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loop detection
incremental regen of entities?