
Hidden line removal
Encyclopedia

This is not the same as hidden face removal since this involves depth and occlusion while the other involves normals.
Algorithms
A commonly used algorithm to implement it is Arthur Appel's algorithm. This algorithm works by propagating the visibility from a segment with a known visibility to a segment whose visibility is yet to be determined. Certain pathological cases exist that can make this algorithm difficult to implement. Those cases are:- Vertices on edges;
- Edges on vertices;
- Edges on edges.
This algorithm is unstable because an error in visibility will be propagated to subsequent nodes (although there are ways to compensate for this problem).
External links
- Patrick-Gilles Maillot's Thesis an extension of the Bresenham line drawing algorithm to perform 3D hidden lines removal; also published in MICAD '87 proceedings on CAD/CAM and Computer Graphics, page 591 - ISBN 2-86601-084-1.
- Vector Hidden Line Removal An article by Walter Heger with a further description (of the pathological cases) and more citations.