CGAL users discussion list

[Yajie Yan <>]

Dear CGAL,

I'm trying to use the fair() function in the polygon mesh processing package to fair the patch of a hole. I have the patch P, and I grabbed the N-rings of the vertices on the hole boundary to use as the constraint faces S. Denote the CGAL mesh M to be the union of P and S. I can then fair only the vertices of the patch using some pseudo-code like this:

fair_vtsRange <- vts(P) \ vts(S) // S is not changing at all

fair(M, fair_vtsRange, fairing_continuity(C)); // C = 0, 1, 2

When C == 0, and the result looks fine (wireframe is shown):

https://drive.google.com/open?id=0B6mEV-kzZjrbYVRPdWwtejdPd2dKem5RUGpkQXBkN3FfRDk4

https://drive.google.com/open?id=0B6mEV-kzZjrbY282dWZyODhJNWdTS2pZTjFJcHNJQkh2YThv

This shows the fair'ed patch and the constraint faces (used 10-rings, but even 1-ring would work).

https://drive.google.com/open?id=0B6mEV-kzZjrbWExYVjAtd05UcU5lazdlOUZEcGluNDJqNkFz

However I couldn't get fair() to produce any meaningful result when I set C = 1 or 2, no matter how big N-rings I have (below I also use 10-rings, which should be enough constraint).

https://drive.google.com/open?id=0B6mEV-kzZjrba1dWeV9QaW0xWXFVa1BQRllFZDhVaTBZc3k0

Meshlab gives me this error indicating the vertices of the patched region after fairing are invalid: "Warning mesh contains 92 vertices with NAN coords and 0 degenerate faces". Even though the hole appears to be not-patched, meshlab tells me there is 0 boundary. So the patch does exist, it's just the geometry is really bad.

I know the fair() might be not be using the best linear solver and cotangent computation can give bad values if the angles are close to 0, but in this test example numerics should be fine.

Any help is appreciated!

- Yajie