Strange mesh seam artifact

Hi, we use baked lightmaps in shadowmask mode

I have a new artifact that I havent gotten before I think its related to one of the newer 2019.3 releases



Its not classic lightmap bleed


Its also visible in runtime (SteamVR)

 

Its isolated to only that place

 

Its visible from flat angles like first post or from distance at a none flat angle

 

Hi thank for reply, it looks like this¨



My settings are like this


I have noticed I get alot less edge bleed with using these settings instead of the auto filter settings

 

I can bake that part of the scene only but its not certain the artifact shows then. will try. The entire scene takes 4-5 hours

 

@JenniferNordwall as I suspected, artifact does not appear when baking only this part. Can try to bake the entire lightmap for this baketag (I have carefully clustered my lightmaps using bake tags)

 

@JenniferNordwall I baked the entire lightmap, there is some artifact there, just not as strong as the other one, plus its not just on one floor mesh now it spreads over several



The overlap is same (thats related to how the UV2 is configured for the mesh)

 

This is not a bleed problem like in that other thread though.

 

@kristijonas_unity I'm not convinved its modular meshes at all. If it were we would have the problem literary everywhere which we dont

Please look here

 

It's possible that it's a mipmapping issue. Would you be able to post screenshots of the mesh's UVs as well as the main texture it's using? If the UVs are mapped right to the edge of the texture, it may be bleeding to white in higher mip levels around the edge of the asset.

EDIT: This could also be the case with lightmap UVs. It may be placed next to a brightly lit area on the lightmaps. Could you also post a screenshot of the lightmap UVs?

 

Hi Archer, Thanks for response. Its autogenerated UV2 becasue this asset does not come with custom UV2 sadly. The UV1 looks like this



The entire floor uses same mesh so shouldn't the artifact cover entire floor if it was a mipmap / UV problem?





Above lightmaps (look for the yellow highlight in both images)

are these two, the problem seam is between these two

 

From top down view I can easily see the seam problems

 

To see if the issue is what I think it is, try selecting the lightmaps in question and disabling mipmapping - that should stop the seams immediately. If not, it may be something else. If it is the lightmap mipmapping, increasing the padding and rebaking should do the trick if you don't have the performance overhead for full resolution lightmaps.

I suspect that at higher mipmap levels (further away from the camera), the lightmap is downsampling and picking up brighter colours from other lightmapped objects nearby on the lightmap UVs. It's hard to tell from the video but it looks like there's no seam when you're close to the objects.

 

As you can see I have some unused space so I have space for more padding, though I was saving that space for increasing resolution for direct shadows in selected places.

Mipmap off for all 3 maps



On, cant see a difference


Its completly removed when up close, so angle of viewing and distance are factors.

 

Actually the artifact is a bit emphasized by mipmaps, if I disable them the artifact line is a little thinner

 

OK, think I've got a fix. There seems to be some issues with the generated lightmap UVs on plane objects. No idea why this is happening, though. It's worth noting too, that this is likely happening everywhere, it's just that the seam is only noticeable in regions of high contrast within your lightmap - you can see seams in the below snip, too, they're just less noticeable.


I managed to recreate your issue - this is with generate mipmaps off in the lightmap - these are 5x10 2m planes, you can see the seams in certain areas where the uv2s are next to eachother in the lightmap.



The workaround is to disable the 'generate lightmap uvs' option on the mesh's import settings - looks like a bug with unity's uv generation. With that disabled unity uses the default UVs instead (which is fine as long as you don't have overlapping UVs). Once that was off (and lighting was rebaked) - here's the result (note that the grid is still on, those aren't seams):



You'll still want to disable mipmap generation or increase padding to avoid the seams in high contrast areas, though.

 

Interesting maybe something for @kristijonas_unity to investigate why it happens to autogenerated uv2s. This fbx has both overlapping and none overlapping uv meshes. Will export the floor mesh to a separate fbx and test your fix. Thanks!

 

btw, im pretty sure this is a regression because I havent seen it until recently

 

@MrArcher can yuo export that scene to a .untipackage and share here? want to test backtrack problem, dont think it will appear in a earlier version of unity

 

@MrArcher I'm working on a repro project so that I can report a bug, but for me there is no difference using auto generated or not



On the right is none autogenerated. I use bake tags so they end up on seperate lightmap

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