View Full Version : Odd refraction problem in Maya 8.5 MR

09 September 2007, 08:43 PM

I am having an odd problem with refractions and bump maps in Mental Ray for Maya 8.5. In the following image I have a NURBS plane which has a bump map on it using a procedural grid texture. Standing up on the plane I have some smaller planes that have transparency and a small bit of refraction (RI 1.2). When the bump map is behind the smaller planes, the bump is getting severely spread out as it gets further from the camera. Has anyone else seen this before? It is almost like the refraction is skewing the bump map before it is applied to the surface, so when the bump is calculated, it is all stretched out. Normally I would attribute it to the refraction, but these planes are perfectly flat, so there should be no distortion, just a slight shift in the image showing through the transparency.

If I turn off refraction, the problem goes away, but of course, there is no refraction :).


(click image for HD res version) (

09 September 2007, 12:12 AM
Anyone? I never have quite figured this out.

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09 September 2007, 12:12 AM
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