Ambient Occlusion gaps between meshes

GitNick

I am trying to bake an AO map and I  get the result you can see in the following pictures. This only occurs on the border area between meshes. I am baking directly from a high mesh to my low poly.

ZacD

Make sure you are using a cage and it's not intersecting. These are projection issues where the baker is either not looking far enough, or it's looking at the wrong part of the model. 

Revel

Or assign a double-sided material on your highpoly mesh.

GitNick

ZacD said:

Make sure you are using a cage and it's not intersecting

So if the knob is a separate mesh from the handle, and each has it's own cage, technically those cages will intersect each other. Is that a problem? If so, how do I multi-mesh AO? I'm doing this in Marmoset using their cage generator. I've tried tweaking the cage offset distances around the knob without much success.

Revel said:

Or assign a double-sided material on your highpoly mesh.

Hmm, I've tried turning on 'Two-Sided' in Marmoset, I think that should do the same thing, but then the white areas just turn dark, as well as the whole knob.

musashidan

It's not a problem if they're separate meshes and Toolbag has an auto-expolde bake by mesh feature(just like S Painter) And if that is the case you could probably do a bake just for AO whth the meshes attached as 1.

Although for such low-poly meshes I would have modeled them as a contiguous mesh and avoid this problem altogether.

GitNick

So, I guess an iteration on my question, does the cage's intersecting cause an issue? Or is it just an issue when it intersects with the high poly of the the neighboring mesh? You are correct, I could be modeling this as one mesh, although there are some areas that would be difficult. Still want to figure out how to do this correctly

GitNick

Still hoping for some direction here. I've even gone as far as making a variety of test models. So far, the most promising is to either bake using groups, which totally removes any AO across objects or to combine and remodel the objects all into a single mesh. In the single mesh case though, it can be tricky. I think the only way to get it right would be to make a custom cage even then. I guess I'm trying to figure out what is the fundamental issue here. I my modeling approach totally off? I thought making a single object of multiple meshes was ok (might want to optimize by removing hidden polys, but still ok) Going to play with a few more ideas, but really running out of runway here.

GitNick

I have attached a simple example model to illustrate my issue:

GitNick

As I think about this issue more, I realized that if you imagined the high poly intersecting with the face, everything behind the high poly sphere is what is white. So I think I understand why it's happening. But this is not a rare occurrence in my models. Whenever the high poly differs a lot from the low, it seems like you'd get this kind of issue. I did try two sided, which at least make the white area dark. Maybe that's the best I can do?

musashidan

What are you baking in? Quick test to show you it's possible and straightforward. This is pretty much default S Painter bake settings. This is a single mesh. What you're seeing in your last image is similar to baking cylinders in that you get waviness due to too little geo on the low-poly(as you've discovered yourself) Can you post the meshes from your original post so we can take a look?

GitNick

Ok, I think I finally figured out my answer. The keys is to make sure that the low poly isn't smaller that the high where the geometries intersect.

musashidan

GitNick said:

Ok, I think I finally figured out my answer. The keys is to make sure that the low poly isn't smaller that the high where the geometries intersect.

Well, this is a fundamental rule in high/low baking. Both meshes should match as closely as possible for best results.

demigodssw

This might help
http://polycount.com/discussion/173259/ao-light-leaks-where-meshes-intersect-in-substance-painter

daniellooartist

musashidan said:

GitNick said:

Ok, I think I finally figured out my answer. The keys is to make sure that the low poly isn't smaller that the high where the geometries intersect.

Well, this is a fundamental rule in high/low baking. Both meshes should match as closely as possible for best results.

On acute angles like that, you always want to make sure the edges are flushed right into the corners. Also, make sure the cage expands past both the high poly AND the low poly.

m4dcow

I remember back in the day people would composite a low res AO bake with the high res AO bake, but this workflow isn't very automated and can compound when there are is alot of iteration. There are higher geo budgets now so this problem is less noticeable but in the above substance painter example the fix is basically to flood the occluded areas with black.

GitNick

Wow, don't know why I didn't see so many recent responses till just now! 

@demigodssw Thanks, I did try some of those Ideas. The Cosine vs uniform I'll have to try sometime. The backface option almost worked, but for some reason, seemed to occlude the whole spherical knob I had at the end of the handle.

@musashidan Ya, the rule was familiar with, what I didn't understand was how it wold affect AO at intersecting geo. Also, looks like we must have responded at the same time above. It shows my response after yours, but I didn't see it till just now. I'd be willing to share, although now that I have a workaround it's not urgent. The finished product is below (I might make one more tweak still though ;P ) I'd definitely be open to feedback.

 https://gitnick.artstation.com/projects/qwVVP