Baking Ambient Occulsion in High Poly or Low Poly?

Amank679

Hi guys,

Ambient occlusion is something I don't have much experience with. In the past when I bake AO I usually do it to low poly objects. 

I want to know if it's best to bake AO after the high poly version of the said object has been modeled or if it makes more sense to bake it in low poly?

Thanks in advance!

Neox

i am not sure i understand the question

usually you have the lowpoly ready and bake the ao from the highpoly down to the lowpolies, like you would do with a normalmap.

Andreicus

I know 3 ways of generating AO in games:

- If you have only the low poly and you use a software like substance painter you can generate all your maps including AO just with the low poly ( you use the low poly as the high poly ).

- If you have an high poly mesh, you usually bake all the maps from the high poly to the low poly, including AO

- If you have an high poly mesh that you use only for materials ID, i don't know about what other people do in this case but i usually bake the ID maps from the high poly and then i bake the remaining maps from the low poly only.

Amank679

@Andreicus Thanks for the reply! That's kind of what I was thinking but wanted to clarify.

I'm not sure what you mean by ID maps, could you please elaborate on that?

Alex_J

Not meaning to be rude here, but if somebody types something and you don't know what it is, highlight the word, right click, and google search. 

You get an answer faster, and you'll not just one persons answer but like, a million. Also, then you can act like a know-it-all. "Me? Not know what a such and such is? No, of course I do!" I've been doing this for years. Nobody has any idea how big a dumbass I really am. Thanks google. 

Eric Chadwick

@EarthQuake outlined a nice combined method here a couple years back. Not sure if he still uses it.
http://wiki.polycount.com/wiki/Ambient_occlusion_map#EarthQuake.27s_Baking_Method

ZacD

If your engine has SSAO, there really isn't a point of having medium scale ambient occlusion detail in your textures. Let the SSAO do its job and don't double up on the AO.

PolyHertz

People used to bake an AO from the low and the high and then combine them, but these days I think most people just bake from the high since the lowpoly and highpoly shapes are generally much closer to each other then they were back then. Plus there's SSAO which helps in eliminating the need for a separate lowpoly AO bake, like ZacD mentioned.

EarthQuake

Eric Chadwick said:

@EarthQuake outlined a nice combined method here a couple years back. Not sure if he still uses it.
http://wiki.polycount.com/wiki/Ambient_occlusion_map#EarthQuake.27s_Baking_Method

I do not. These days I use Toolbag for all my bakes (shocking, I know). Toolbag has bake groups which prevents intersection errors, so there is no need to manually explode meshes for bakes anymore. There is a setting to ignore the groups for AO, which casts AO from group to group, so you can get fully correct AO without any extra steps. There's a setting in each Low object that allows you to flag certain meshes to be excluded from this behavior too, so if you have a part that needs to animate or be removed you can make sure it doesn't cast AO to/from other objects.

All of this is should be covered here: https://marmoset.co/posts/toolbag-baking-tutorial/

Generally speaking, calculating AO from the low poly can introduce shading errors, and of course the level of detail that you'll get will be much lower than if generated from a high poly mesh.

EarthQuake

ZacD said:

If your engine has SSAO, there really isn't a point of having medium scale ambient occlusion detail in your textures. Let the SSAO do its job and don't double up on the AO.

AO is used as a source to generate various effects in the texturing process, so whether you have AO plugged into a shader or not, it's still good to have a sensible workflow for baking a good map.