is it possible to have a button to overide all materials to just a flat grey? for lighting test rendering?
Chris
You can do this using a render layer override. Just create a new render layer with all objects in the scene. Then right click on the render layer in the render layer editor and choose Overrides → Create new material override.
Greetings,
Vladimir Nedev
Maya 2008 and 2009,
have a bug (maya related), so I’d recommend creating the layer, and selecting all objects in the layer, and just assigning the shader
instead of “global layer override”… 
Cheerio.