Face Regions (Hatching support)

The HLM can be used to identify the visible and invisible regions of a face to support hatching or shading operations.

Local and Boundary

When two parts interpenetrate, it is possible to include their curves of intersection in the hidden line view.

Interpenetrating Parts

The animation opposite illustrates the hidden line views that are computed as a cylinder is lowered, interpenetrating first with a cylinder and then with a parametric surface.