Hi! I'm playing with https://developer.nvidia.com/orca/amazon-lumberyard-bistro dataset and meshoptimizer and I've noticed this particular failcase related to the way the corners were authored.

For example, here is the original chair mesh:

Notice the rounded corners with shared vertices. They survive the first pass of meshopt_simplify to half the number of triangles fine:

However, once the triangles between two sides facing at 90deg get folded and the sides start sharing the vertices, the vertex normals can no longer be correct:

What would be a solution to (automatically) preventing this?

I was thinking of adding additional custom skip code in the 'pickEdgeCollapses' loop if angle between vertex normals is above certain threshold but I'm sure there's a better/simpler solution, perhaps already there? :)

(instead of preventing collapse, could also allow it but duplicate verts so normals aren't shared?)

Thanks for the great library!!