ambient occlusion bake with multiple amterial instances

Ok, there’s lots of tutorials on baking ambient occlusion and I can do it - though it seems to take aaaages for me. What I am worried about is I have a relatively complex model that I am trying to bake and it has several material instances and UV unwrapped areas. Think of it as a character whose arms have a different material to its torso. When I try to bake just the selection (say one arm) it bakes the entire object.

I haven’t got to the texture creation part yet but I’m worried that the bake isn’t going to work as the UV’s needed to wrap around the entire object are different to the UVs for each material instance. Sorry if this sounds confusing but an AO bake (even on approximate>default settings) maxes out my quad core for over an hour with this model, so trial and error is a bit annoying. The mesh is about 10,000 verts without subsurf - I’ve not baked before but looking at video tutorials I swear there’s something wrong. :frowning:

I also find it confusing that if you load an image in the UV/Image editor it wraps it to an object and seems to override the material setting (at least in the 3d viewport).

So…

  • Has anyone had experience with baking to an object that has multiple materials and unwrapped UV areas?
  • When baking does it always bake the entire mesh not the selected area?
  • If so then how do you incorporate the bakes in a situation where you have overlapping UV unwraps (the multiple materials thing)?

Cheers.

Oh and typo in the title (not sleeping much atm): “ambient occlusion bake with multiple material instances”.

Aha! Logical work around is make a duplicate of the model (or duplicate file) and for each material index selection (the faces assigned the separate material) isolate them by deleting the rest of the model. Then bake that - which finally produces results, doesn’t take 20 hours, and doesn’t crash Vista desktop!

A bit cubersome as I have 11 materials so I’ll have to select/delete a lot of areas. But I don’t care cause it looks like it will work!!