Bake AO using Self Occlusion?

DustyShinigami

Hi

This might be more of a feature request than anything, or I simply haven't used the right settings, but, is it possible to bake an individual element, or everything together, using Self Occlusion? Or to adjust the AO, so it better captures inside crevices?

With a test bake I did, I keep getting these white patches inbetween a chair's cushions, like so:

I tried adjusting the sliders for the AO's preset, but nothing seemed to fix it. However, in Substance Painter - and I'm guessing this is due to the Self Occlusion option...? - it does a much better job. It's normally set to Always, but can be set to Only Same Mesh Name, which can be useful if something else's occlusion is being problematic and bleeds onto something else.

Before:

After:

By Same Mesh Name:

Thanks

EarthQuake

Try enabling the Two-Sided option

DustyShinigami

Oh, okay. Hang on - will give it a quick check now. Thanks.

DustyShinigami

Awesome! Thank you so much! That worked perfectly.

EarthQuake

Cool - yeah so the issue here is if there are intersecting meshes, some of the rays can end up inside the mesh at the borders. If double-sided isn't on, the rays will shoot through the surface.

Creating water-tight low poly meshes without intersections may help to avoid it too. This will also tend to reduce the triangle count and make it easier to optimize UVs (as you're not spending resources on areas that are hidden inside other objects). If an object doesn't need to animate or otherwise break apart this is generally a good idea.

DustyShinigami

Okay. Food for thought. Although, my way of thinking, which was hammered into me back in 2019/20 was to model things like they would be constructed in real-life...? In this case, the cushions/parts of a chair...? Although, I guess that rule doesn't have to apply here because of baking...? And it would apply more to modelling a low poly asset with no baking required...?

EarthQuake

I would say that applies more to the high poly. The low poly should be a shell around the high - unless the object needs to split apart for some reason, in that case, the internal areas should be modeled. 

Here's a simple example of an object made up of intersecting spheres. The version on the left uses 30% more triangles and would have a significant area of wasted (unseen) triangles in the UVs.

DustyShinigami

Hmm. So if I were to have them separate, like I have done with these chair cushions, is it fine to intersect the UV shells like that without getting any baking problems? And the AO would bake correctly in similar crevices?

But I'll certainly keep that in mind when making something similar in future. Thanks.

EarthQuake

I would say no and no. The AO artifacts are due to the intersecting objects - so the way to solve that is to merge the objects or enable the Two-Sided setting. I wouldn't recommend overlapping UVs - this might cause other problems as the faces are unlikely to line up perfectly. You could isolate the UVs that are completely hidden and make them small in the UV layout. But if you're going to take extra steps to handle this the effort is better spent removing the unnecessary geometry, which will solve the UV problem and improve the bakes.

Here's a more practical example - a tufted cushion on a wooden base. The button, cushion, and base are all separate objects in the high.

The low is a single shell that covers the high. The large planes where the pillow and base intersect get deleted and the objects are merged along the border. The button isn't modeled because it can be represented with the normal map. 

DustyShinigami

I see, I see. The process you describe has come to mind with a previous project before. It's really a case of thinking and deciding what and where things should be just baked onto the Normal map rather than manually retopped.

EarthQuake

One other benefit you'll see from merging objects in the low poly mesh is reducing aliased geometric edges. Anywhere that you have objects intersecting like this you'll see this kind of aliasing. But if you merge the objects, the seam between them will be anti-aliased in the bake and look cleaner.

DustyShinigami

Ahh, cool. Thanks for the tip. Yeah, that has been a frequent issue in my bakes. Definitely something I'll need to keep in mind for future projects.