Unity 5: Light Leaks at UV seams

Hi all,

after baking a couple of scenes in Unity 5 I noticed a persistent problem: At edges where the lightmap uvs are split there are notable light leaks. It looks light blank space of the lightmap (->black) bleeds into the texture space occupied by the uv2s. I tried to increase final gather but it didn't solve the issue.

Any ideas how I can prevent this, or is it possibly a bug and can be fixed by dilating lightmaps?

The top image shows the leeks I'm talking about, the second one visualizes the uvs.

 

The reason for that is most likely the lack of dilation.
In Unity 4 we were using a very quick push-pull dilation algorithm that was running as part of the import.
In Unity 5 we're not using it yet as we didn't have access to the mask of which pixels are the background and which are not. That functionality was added in Enlighten and we'll make the dilation work again soon.

Could you perhaps file a bug report with the repro above, so we can check on our side if that fixes the problem?

 

Oh I see, thanks for your detailed explanation! Now I understand the problem better, and glad you're working on a solution

I will gladly file a report to provide a working example for you and gonna write the case number here.

 

Ok, all done! Case number is 682143.
Thanks in advance!

 

I'm having a similar problem as well. Is there anything we can do in the meantime?

 

It's possible to dilate lightmaps manually in photoshop using some script/action. But that's not practical if you do it for all the levels in a game project. Guess we have to wait :/

 

Thanks for the repro, @essimoon2.
And yes, you can ofc dilate them in an external program, but it's fighting a losing battle. We'll try to get the fix into a patch release, so you can get it ASAP.

 

I am having this problem too.

I guess I will have to wait for the next patch!

 

Any update for this issue? I encounter this in Unity 5.0.1 too. Increasing resolution help but there is always visible leaking.

 

I too am seeing substantial light leaking, regardless of what precautions I take on my end. A fix to this would be most appreciated!

 

The main issue is that the spacing between UV charts of your object is too low. So charts are fetching lighting data from neighbouring charts.


This can be fixed by changing the Pack Margin on the model importer. This adjusts the padding between the charts. The value is measured in texels, but assuming the mesh will cover an entire 1024x1024 lightmap. Of course typically it will be covering only a small part of it, so to get a reasonable margin, you may need to increase that resolution.

For this object with the current resolution the value of 40 works well.

We are planning to adjust the padding between the charts per instance, which will mean that we'll simply use the padding property from the Lighting window both between the objects and between the charts. A lot of people are running into that issue and we finally have means to fix them (per instance UVs).

The other issue is that if one changes the mode from Non Directional to Directional or Directional Specular then it turns out that we were missing a one texel dilation margin in the directionality texture. This is fixed now in 5.1 and we'll backport the fix to 5.0.x.

Another issue, I initially though you're running into, is us not filling the background properly. Generally this only matters if you're seeing one of the smaller mip levels on your object. I didn't find that to be an issue in your case.
We will fix this as well though.

Hope this helps!

 

Thanks for your detailed reply, Kuba! That's great, gonna try it out as soon as possible.

 

Hi Kuba,

I have the same issue in my scene and we create our lightmap in external software.

It is a clear padding issue in the baking engine. You can add an option for this?

Thanks

Take a look to this reference:

 

Although the issue on my particular asset is fixed we still have problems due to missing dilation in Unity 5
Any updates on when it will be ready?

 

Baked lightmaps need some love. Dilation is obviously a must have, it's very hard to make things look correct without it, but also, final gather needs some much needed love.

I was one of those that weren't satisfied with "just" the upsampling of the realtime data for the bake. So you gave us Final Gather. Now every pixel has unique data. Cool! Awesome!

But...

Your final gather implementation is the brute-forciest implementation ever. There are a ton of techniques around (importance sampling, adaptive sampling, maybe combining it with irradiance caching etc etc), so that maybe, maybe we can find a way so that I don't need to crank the rays up to 20000 just because that little luminous poly over there is generating a TON of noise (but everything else looks cool with a fraction of the rays).

 

Bump

 

Any update on the dilation? It's been a while and after updating to Unity 5.2.2 the problems seem to have gone worse

 

Yeah, I'm having some issues with light bleeding through my object. Tried different values for the model but nothing works. Ticket raised: 741588.

 

Ok, managed to fix this. I've set the Cast Shadow property on my prefab to Two Sided and that fixed the issue. The Shadow Bias was 0.04 and Normal Bias 0.05.

 

I also have this problem. I filled a bug report with a simple scene that has the problem, bug report 785185

It seems I need something casting indirect light to make the seams appear, but in the project I am working, indirect light is the makority of the light and seams appear very easily


The seam exists even if there is two free pixels between islands on the lightmap (I am only using meshes from Unity here)

 

Has there been any word on lightmap dilation? Still broken :/

 

Will this ever be added?

This is a major issue. Engines from 1997 have no issues with black bleeding and they have much lower res lightmaps.

Is it really any harder than extending the colour of the pixels outward after baking?

 

Hi @Kuba,
Two years have passed since we were promised the dilation, but we still don't have it. We use unity 5.5 and have annoying seams on smaller mip levels. Could you give us any update on the issue or suggest any workarounds we can try?

 

Yes, please fix this! This is a constant issue for me.

 

Yeah, I just want to say as well that this is is something a lot of people would appreciate to be fixed.

 

Yup, would really like to see this fixed...

 

Is it not fixed in 2017.3 for you?

 

2017.3 is beta, haven't tried it. Did this fix it for you?

 

+1, is there anybody that tried out .3 that's able to verify that it's finally been fixed?

 

The progressive lightmapper has an option to stitch seams (the option is on the mesh renderer) that works quite well.

Other than that, having UV seams in your model, will almost always result in some discontinuity in lightmapping, so proper UV making and making sure you hide the seams is something everyone should do (even though the progressive lightmapper does a good job of hiding the issue).

 

Well of course, that's why I make my own uv2 channels . Still, a little bit of dilation goes a long way.

 

Sure, but I think that the latest examples of the issue are not an issue of dilation.

 

@AcidArrow considering the last comments on this thread were regarding dilation, what latest examples are you talking about? ( havent done much lightmapping in recent months, so I probably am out of the loop )

 

forestrf's last post is not an issue of dilation. Lack of dilation usually produces black (or white, or whatever the background color is) "bleeding" where the seams are (which is exactly what happened in the first post in this thread.

forestrf's issue is not lack of dilation. There's no bleeding happening there, there is just a discontinuity in the lightmapping because there is a discontinuity in the UVs.

 

It may not be lack of dilation, but while the discontinuity in the UVs doesn't affect direct lighting there, it does with indirect lighting. If there are no bounces, there are no seams :/

 

The progressive lightmapper does stitch seams quite effectively though.

 

I want to try it tbh. Problem is, right now I don't need lightmaps :/

 

And the post right above forestrf's was mine about dilation that I was seeing in the lightmapper.
However, just like forest, I'm not doing any baking at the moment, but it's definitely something I'll run tests on when I get a free hour or so.