On the left side of the fireplace firebox--what is causing this dark interference-type pattern?
I think I have eliminated the obvious suspects:
- coplanar faces
- mapping coordinates
The render is in Mental Ray using final gather; but changing the final gather settings does not change the strange pattern.  The brick material looks perfect in the viewport but renders strangely in a single frame, and the pattern moves like an interference pattern when rendered with a moving camera path. (see video:
http://www1.thelogconnection.com/animations/FP-problem3.avi

--3ds Max Design 2009 64bit, Direct3D 9, Win Vista Premium 64, 3ghz quadcore Xeon, Quadro FX1700--

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Is there glass on the fireplace? I’m wondering if this is causing some kind of refraction related artifact.

Oh for...I switched to perspective view and changed my view angle, and it rendered properly.  And now if I switch back to the camera view it renders properly.  Whaaa?

(EDIT--but now the #@$% forum software won’t let me attach a jpg.  They really need to fix this.)

--3ds Max Design 2009 64bit, Direct3D 9, Win Vista Premium 64, 3ghz quadcore Xeon, Quadro FX1700--

I’m not sure if this is the problem but it might be worth saying. In the past I’ve had loads of problems with final gather and glass. Seemingly final gather tries to ignore the glass, then gets confused when rendering nearby surfaces. I’ve found setting the glass transparency to 0.99 instead of 1.0 and its diffuse level to 0.01 (with the colour set to white) can sort this out. Could be worth a try…