Ambient Occlusion - Is it really necessary?
polycounter lvl 6
Didn't really want to create a new topic for this but couldn't find a quick question thread 
I've noticed that in Unreal 4 I have the option to enable post processing AO, which adds some nice contrast to my models. Since this feature exists, is there still a benefit to baking an ambient occlusion map in PBR materials? My AO maps never seem to do much... so I'm wondering if I'm doing something wrong here.
Also, when baking AO on an exploded model, it seems more logical to create a separate bake with the model fully intact - in order to get accurate occlusion. Is this something industry artists do?
Thank you ^_^
I've noticed that in Unreal 4 I have the option to enable post processing AO, which adds some nice contrast to my models. Since this feature exists, is there still a benefit to baking an ambient occlusion map in PBR materials? My AO maps never seem to do much... so I'm wondering if I'm doing something wrong here.
Also, when baking AO on an exploded model, it seems more logical to create a separate bake with the model fully intact - in order to get accurate occlusion. Is this something industry artists do?
Thank you ^_^
Replies
With that said, using AO as a map is up to you, if you don't feel it adds to the overall material, then don't waste the color channel. I do notice the impact a good modern AO does, so I use it.
And yes, if you want to bake the large scale AO then baking the full model together is your best bet for accuracy.
As an added benefit, baking the AO map also allows me to material blend in Unreal with more control.
And for baking, when you explode the meshes and bake AO I always find the best results by combining my high poly AO with an AO map generated from an unexploded low poly mesh. This gives you the detail of the high poly with the occlusion that would naturally result from the actual final model itself. The exception is any animated pieces like the bolt of a gun that must move back. You wouldn't include that in the unexploded low AO bake, since it moving positions would mean the AO map would then be wrong.
That's a great answer and workflow. I'm going to give it a shot.
Still, you may actually want the AO produced from your low to be blended in your final AO map as it still offers extra detail where the high and low are mismatched at all. So you could do it like you said AND bake a low AO map, then take the minimum value of both ("Darker Color" in Photoshop). Even in instances where I've baked high AO that self-occludes it looks better to me when both are combined.