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# How to find uv coordinates for a 3D triangle?

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### #1larspensjo  Members

Posted 04 January 2014 - 04:21 PM

I am using the uv coordinate as a seed for a 2D simplex noise to create surface effects. If the triangle has the normal pointing at z, then xy can be used as uv coordinates.

However, the triangles have more or less random orientations. I suppose I need a rotation so as to have the normal aligned with e.g. z, then I can again use xy as uv. I have difficulties to find out how to do this rotation.

It may be that the problem can have more than one solution, but I only need one. Is there an efficient algorithm for this?

Current project: Ephenation.
Sharing OpenGL experiences: http://ephenationopengl.blogspot.com/

### #2unbird  Members

Posted 05 January 2014 - 03:43 AM

You could play with tri-planar projection, like shown in this GPU Gems article. But I rather recommend using a 3D noise as source, so you can feed the positions directly.

### #3larspensjo  Members

Posted 07 January 2014 - 03:46 AM

There is an implementation of 3d Simplex noise at github/ashima/webgl-noise. I was mainly worried about higher performance costs as the 3D noise is more complex than the 2D noise. But it turned out this added a negligible time to the shader.

Current project: Ephenation.
Sharing OpenGL experiences: http://ephenationopengl.blogspot.com/

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