Why does my subdivision modifier appear to ignore some creases?

Question

I am applying the subdivision modifier to my low poly mesh, ready for baking. With every edge set to mean crease 1, I end up with this:

Almost everywhere the creasing is working properly, but the subdiv is clearly ignoring it for the largest front face and in a few other places.

Wherever this occurs, it looks as though the subdiv is resulting in 2 faces on top of each other with conflicting normals, as turning on face orientation looks like this:

Any ideas as to what could be causing this?

Answer 1 · 2021-01-07T22:54:46Z

d

replied January 7, 2021 10:54pm

After thinking some more I realised that subdiv really wants to work with quads so I have started to cut up the n-gons around the problem areas and this is fixing the problem. I'm adding a few vertices to the model but I think I will live with that.

Answer 2 · 2021-01-08T18:31:21Z

Jonathan Lampel replied January 8, 2021 6:31pm

That would do it! Tris or quads help hold the perimeter in place.

Answer 3 · 2021-01-08T18:55:18Z

d

replied January 8, 2021 6:55pm

Oh you've made me realise, I removed the triangulation modifier when I added the subdiv, if I had just applied it instead I would never have had this problem, and I wouldn't have needed to add any vertices. Well I feel silly but at least I'll know for the future, thanks Jonathan.