View Full Version : Vertex normals

09 September 2011, 08:17 AM
Hi there, I have the following problem, I need to make a tool that generates collada files with cylinders in it. Now I am a bit puzzeled by vertex normals.
For example in maya if you create a cylinder, the vertices on the circles have 3 normals each, while the vertices in the middle (top and bottom) only have 1 vertex normal.
How is decided how much normals each vertex has?

If you export it to a collada file, the normals are just exported as a list of vectors, and there is no information about which vertex has how many normals, or which normal belongs to which vertex... so any idea how this works?

09 September 2011, 11:59 PM
Hey sttrife, in Maya, a vertex that has several normals is considered a "hard edge" and has no smooth interpolation in between the faces. To accomplish this, you end up with a normal per vertex-face which points in different directions (basically a mesh discontinuity)

This is handles differently in many programs (IE Houdini cusps edges by splitting the vertices). My guess is that collada (without knowing too much about it) accounts for this by storing a normal per vertex-face, even if they are continuous

Hope this helps!

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09 September 2011, 11:59 PM
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