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### #ActualCatmull Dog

Posted 03 August 2012 - 07:52 AM

Ideally, you will use Vertex normals (take a weighted average of the normals of all adjacent triangles sharing the vertex at that point). This is easier to calculate if the surface is on a regular grid. For polygon soup you may not know all of the triangles that share that vertex.

If it is as a parametric surface, the normal at u,v is (basically) the cross product of the vectors: (u,v)->(u+delta,v) and (u,v)->(u,v+delta) where delta is the tolerance, normally based on the surface sample resolution.

But for starters, just use the polygon normal (normalized cross product of two edges of the nearest triangle).

### #1Catmull Dog

Posted 03 August 2012 - 07:52 AM

Ideally, you will use Vertex normals (take a weighted average of the normals of all adjacent triangles). This is easier to calculate if the surface is on a regular grid. For polygon soup you may not know all of the triangles that share that vertex.

If it is as a parametric surface, the normal at u,v is (basically) the cross product of the vectors: (u,v)->(u+delta,v) and (u,v)->(u,v+delta) where delta is the tolerance, normally based on the surface sample resolution.

But for starters, just use the polygon normal (normalized cross product of two edges of the nearest triangle).

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