This shader processes the depth map of the jit.freenect.grab external and outputs
perspective-corrected x,y,z vertex coordinates for use with jit.gl.mesh and others. It expects
jit.freenect.grab to output in mode 0 (raw).
Based on the math at http://openkinect.org/wiki/Imaging_Information.
Shader by Dieter Vandoren (http://dietervandoren.net).
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