I am new to Unreal Engine and I have a couple of questions about Lightmass. There is some inconsistent light bleeding through and between flush objects that is unexpected. If I can understand what is behind these results, I can make allowances for this in the 3D art I hope to produce.
The following scene images show all the brushes in a test scene. I have added one small subtractive brush that produces the lighting I first expected to see before I added the subtractive brush.
I am new to Unreal Engine and I have a couple of questions about Lightmass. There is some inconsistent light bleeding through and between flush objects that is unexpected. If I can understand what is behind these results, I can make allowances for this in the 3D art I hope to produce.
Hi Alan,
I think your images got out of order for the With/Without subtractive brush. I was able to see what you’re seeing though and will provide a little context to hopefully help.
When you add the subtractive brush to the scene you will need to rebuild the lighting to get the results you need. When you add or move something it will break lighting and some objects will need to be rebuilt to look correctly.
For the light bleed if the objects are sitting flush you should get no shadow bleed. If you move any of the verts so that they are not flush you will allow that bleed to pass through. Again, you may need to rebuild the lighting here because it looks like it was not rebuilt in the images after adding the subtractive brush.
To further touch on light bleed. Make sure you build on Production lighting quality when testing light bleed issues. By default it is set to “Preview” and it’s just that; a preview. It will give you an idea but it will not be fully accurate with baked shadows. If you’re still noticing issues there, you’ll need to look further for troubleshooting that may be with the mesh placement or with the UVs for the mesh. Longer objects that stretch out will often bleed lighting because this is not conducive with a properly setup lightmap UV.
Try rebuilding light and let me know if that helps.
The images are in the correct order and rebuilt with production lighting every time. All meshes are your standard BSPs, so UVs should be fine.
What I note is that when I add a small subtractive or additive brush to the larger volume it prevents light bleed in allot of cases.
What I don’t know, is why. I have done several experiments.
Does it have something to do with photon casting density or vertex alignment?
Maybe there some constraints about intersecting BSPs resolving into a solid volume. At this point I’m speculating and need your help.
There was a comment you had the other day here that indicated you still had the issue. I see it’s been removed though. I wasn’t able to respond the other day and was going to look at the setup and see if I could help further, but it appears to be gone.
Sorry for the delay.
I had a look at your suggestion and wasn’t able to make it work for me.
I’m doing more tests to see if I can resolve.
One thing I thought maybe able to help me is ‘Show Shadow Traces’
When I enable, I don’t see any indications. How is this feature supposed to be used? Perhaps you could show me an example. I can’t find this in your docs.
Alan
I spoke with the Rendering team regarding these and that is a bunch of code brought over from UE3/UDK that is no longer relevant. It’ll be removed post GDC at some point.
