Thin Black Lines in AO bake

Trevor · Apr 2013

I am having a problem with thin black lines running across some of the UV islands in my AO bake. I am at a loss to what is causing this problem since the shading looks accurate in the problem areas and the normal map looks good. I did model low to high poly in this case (not sure if that matters) because im going for a simple non sculpted shape. I have attached images of the problem below along with my Xnormal settings used for the bake. This problem is small enough to just paint out in Photoshop but I would like to find a solution to this problem to minimize time spent on image doctoring. Any help would be wonderful!

Bartalon · Apr 2013

Are you using a cage? I found cages have resolved nearly every baking issue I've had in the past.

Trevor · Apr 2013

I am using a cage and the problem exists with or without the cage.

Edit: My cage has sharp edges (smoothing groups) because if i take all the sharp edges off Xnormal wont accept my cage because im exporting from Blender using .OBJ format. Could the sharp edges be the problem? Should i just export an unsmoothed cage into Xnormal, edit it using Xnormals editor and save as ,SBM?

Jet_Pilot · Apr 2013

you might want to check you don't have any extra verts or edges in those areas. Try selecting everything and wielding to a very low number like .01 so you don't see any noticeable difference, like it collapsing chamfer, and see if the vert count changes.

dtschultz · Apr 2013

It looks like the tris are showing up in your AO bake. I wonder if you turn your tris if that would fix it.

Trevor · Apr 2013

Checked verts, no extra verts, reversed tris, and the artifacts remain:poly127:.

J0NNYquid · Apr 2013

I know you said the normal bake looks good but just for the sake of trying another aproach what if you put your whole model on 1 smoothing group and just see what sort of result you get, I know when I've run into issues before that has worked. Not for every situation mind you, but it's worth a shot. I'm not versed in the Blender to XN workflow so that may be poor advice.

Trevor · Apr 2013

Im not too clear on how the smoothing group situation works when trying to do that in Blender. All I know is that Blender uses "sharp edges" which splits the whole geometry at the edge defined as sharp and I have heard that Max splits it at the vertex normal only (please dont quote me on that as I am really not sure).
I did try the bake with NO sharp edges on model and cage and it turned out the same.
With Blender it seems that my low poly and cage models have to match while keeping all sharp edges on my cage and low poly the same (since it splits the vertices) when I export in obj format. When I look at other tutorials I see smoothing groups on the low poly and NOT on the cage and the bake comes out clean. Am I just interpreting it that way or is that the way it works?? When doing this in Blender it seems there is an exception for everything.

cptSwing · Apr 2013

I have usually have this occur when I bake from lowpoly to lowpoly in xNormal - try upping your angle bias (is that what it's called?) in your AO settings maybe.

Trevor · Apr 2013

Upping the bias just made the artifacts worse in the problem areas. I tried subdividing my high poly 4 times, exported, rebaked, and got the attached results.
since the results actually changed, is the problem my high poly?

leleuxart · Apr 2013

You said you're using a custom cage from Blender? Have you tried the XNormal cage?

cptSwing · Apr 2013

Flipped normals possibly? And your LP Uv's? No overlaps, no flipped faces etc?

Trevor · Apr 2013

I recalculated the normals multiple times along with multiple visual checks, no duplicate verts, no overlapped uvs, no flipped uv faces.
Im not sure how to setup a cage in Xnormal. it doesnt save the cage when I save meshes out of the 3d viewer.

Thin Black Lines in AO bake

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