Ambient occlusion for an entire scene

[A_GAME]

I want to show the ambient occlusion pass for a breakdown of my scenes in my demo reel. I was wondering what is the work flow for doing ambient occlusion for an entire 3d scene.
I have done it on single objects, but when ever I try to attach my shader to the scene and push render, it all comes out black. Anyone have any ideas?

[rburke]

there is a lot of things to consider here. First of all it will come out black if you have overlapping uvs. But this can be remedied by baking stuff in sets and also buy changing the bake options. The multiple objects thing and the bake to one map settings will both effect this. What works best for me is this. I break things down into groups, then i use the second uv set AO pass thing. Apply the surface shader to the whole scene, now choose the group the objects however you like trying to avoid overlapping uvs. If your using a second uv set you can combine all the objects in one group, and then auto map the second uv set and bake to that. If you are not then you will need to do more separate bakes. What is good to remember is that you need to have the surface shader on anything you want to affect the ao pass. So after you bake one set of objects it will automatically put them on a new lambert. well when you went to bake the second set that first set would not effect the bake so you would need to make sure after baking you reassigned the surface shader. Also it goes without saying but change the name of the file you are creating each time you move onto a new group otherwise you will be overwriting the file and you'll loose your first set. There is a little tutorial in the tutorial section about second uv sets and light mapping, read that should help you out some. IT will be easiest to learn this if you make a little practice scene to try it out. You technically can bake the entire scene at once but it tends to be really slow, and also makes resolving errors much harder.
im at school on wed's this summer but not this weds but i could explain it better in person.

[Amad]

Austin there's a rendering method to get AO without UVing at all. I don't remember how to do it, but I know that there are render settings to achieve it. I'll try and dig up my old files that I did it on and see what I did.

Check in your settings near where you'd find image based lighting and HDRI stuff. I'm fairly sure there's a setting for Ambient Occlusion. You couple that with a surface shader as you normally would.

I could be totally off-base with the 'how', but I'll find it and let you know.

[rburke]

yeah if you render with mental ray you can show AO, wont be the same as backing it but it will actually look nicer. IT just wont be an in veiwport thing. The last option in global illumination panel of the mental ray render settings you can turn AO on.

[A_GAME]

Thanks fellas. God I love this site.