I’m trying to create a shadow map for an architectural walk-through by baking the foors, walls, and ceilings of each room. However, what I’d really like to bake is just the shadow pattern, not the arbitrary textures I have assigned to these elements right now. I figured “hey, I can use the White pass I wrote about a few weeks ago”. I set my Render Material to a nice white color, but the baking uses the object’s assigned textures, not the texture override I specified in the Render Layers dialog. Is that a bug?
Baking occurs on an object basis. The material override is for rendering purposes and has nothing to do with the materials assigned to the objects themselves. Try creating a duplicate scene (full copy) and set the material override to a material set to shadow only. Put all objects on separate render layers. Render with each render layer having a separate and properly named image out put node. Save these images in a format that supports transparency. Then add an image texture to each object in this scene which corresponds the proper image that you just output as shadow only set it’s blending mode on the map to tab and bake. I haven’t tried this but I’m confident that it will work. I say use a new scene so that you don’t inadvertently destroy your original. You just may have to play with it for a while to achieve the desired result. I haven’t actually tried this but I am 100% confident that it can be done, it just may not happen exactly as described above.
Using a high sample rate for AO and outputting the image as an AO pass only would eliminate a lot of the work.