[chrisnvp]

Here is the issue:
My client doesn't like the material he chose for the front of his building.

My Question:
Is there a way to change this material and then re-render the scene with all the other objects in the scene hidden but still interacting and affecting the new material? (ie reflections and shadows, clipping ect...) I would like to end up with an image I can just place over the first rendering and it would fit like a puzzle piece over every part of image where the existing material was showing.

Reason:
I'm trying to avoid re-rendering the entire scene and wasting time rendering stuff that is already complete. (If there was glass in the project that had reflections of the old material, I would have to re-render that as well, but it would still be way faster than re-rendering the entire scene.)

If this already is possible.... feel free to call me an Idiot.

Thanks
C.

[Bubbaloo]

You can render an object id pass, and then do a region render of just the affected area and use the object id pass as a mask in PS to "switch" the materials. I've done it before.

[brodie_geers]

I believe you can just hide all of the other objects from camera. Just don't hide them from GI or Reflections and they should interact with your material as if they were being rendered in the scene. Only drawback is that if any of your hidden objects would normally be blocking a portion of your rendered object it won't block them any longer. Solution is simply to delete those sections post-process.

-Brodie