[Smtk-developers] Polygon question

[David Thompson]

Hi Bob,

I have a question about how many corner cases the polygon session should handle:

  should users be allowed to create non-manifold models?

The case I am worried about is if (see attached figure) a user creates
- face 1 with vertices A-B-C-D-F-G and then creates
- face 2 with vertices A-B-F-G and then creates
- face 3 with vertices B-C-D-F.

In that case, edge A-B (for example) is used twice in the same sense.
Vertices B and F are also troublesome.

The data structure I use for vertices and edges will be different depending on what you say. If I only have to track manifold models, then it is enough to store a list of edges in CCW order at each model vertex plus a list of face IDs between pairs of adjacent edges (and nothing at edges except model vertices). If I have to handle non-manifold models, then edges will have to store lists of loops and vertices will not store faces between adjacent edges (or will have to store a map between pairs of edges and faces).

Any opinions?

	Thanks,
	David
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