Light Leaks

alexworx

I am in the process of working on my first UE project. Its going slow but I am learning a lot and love the program. Here is my latest build. I am using a skylight with a hdri map along with lightmass portals in the window wall.

I am getting weird light leaks in areas as you can see by the enclosed images. I also enclosed my light mass settings as well. I have not tweaked my BaseLightmass.ini file.

What should I be checking to get ride of those leaks?

Thanks

Alex

Obscura

First I would try playing with the static lighting level scale. Also, whats the lightmap resolution of those meshes? Are you building the lighting on production quality?

alexworx

Should I put it lower or higher for the static light level? The walls are at 512 and yes its on production quality.

Obscura

First I would try and see how does it look when its set to 1.

alexworx

will do. thanks

leleuxart

Are your meshes closed as well? Open faces in the back or top of the walls can cause light leaking too.

Daniel_Swing

I'm also investigating what creates light leaking in UE4 (I say investigate because I don't really have a clue).

leleuxart said:

Are your meshes closed as well? Open faces in the back or top of the walls can cause light leaking too.

This is what seems to be working for me. I'm just wondering: Is this necessary to making sure that no light leaks through? I'm just thinking that it eats up a lot of UV space and adds a bunch of "unnecessary" polygons.

Obscura

You can scale down those polygons on the uvmap so they don't take that much space. You won't see them anyways, so its not a problem if they are lowres.

leleuxart

Obscura said:

You can scale down those polygons on the uvmap so they don't take that much space. You won't see them anyways, so its not a problem if they are lowres.

This. You'll be adding additional polygons, but it shouldn't really be that much and you don't have to worry about triangulation or anything, as long as it doesn't effect the visible faces. One thing to keep in mind with adding these extra faces though, is when you do make the Lightmap for them, keep the faces that will never be seen disconnected from the visible faces in the Lightmap. This helps reduce shadow bleeding onto the visible faces.

Ootrick

If you're using a modular setup for the ceiling tiles you might need to merge/weld them as well, lighting an interior with the direct dominant can be difficult at times. Make sure your meshes are double sided too, if that's the case! good luck, looking great  

Daniel_Swing

Well, that scratches my itch and curiosity. Thank you!

Tzur_H

Obscura said:

You can scale down those polygons on the uvmap so they don't take that much space. You won't see them anyways, so its not a problem if they are lowres.

sorry, but does this also applies to lightmap UVs?

Obscura

Of course. You don't see those faces to their pixel density doesn't matter.

kelheor

You have to make a separate UV set for lightmaps in 3D modeling software.

All your UV borders should be snapped to the grid to prevent light bleeding. You have to setup your grid according to your lightmap resolution (try to start with 1/64 = 0.015625).

You have to get at least 2-4 px of padding between UV shells to remove seams and light bleeding.

Then you need to change lightmap size for your models in UE4. Start from 64 and try to increase values up to 1024. You can do it in mesh editor or by overriding lightmap resolution for certain models in your level. Use lightmap density viewmode to check if resolution is enough for your meshes. If you see green everywhere with a lowest possible values, then you set up everything correctly.

Also turn off "Compress lightmaps". In this case you will get much better result with a lower lightmap resolution. 

Mant1k0re

kelheor said:

Also turn off "Compress lightmaps". In this case you will get much better result with a lower lightmap resolution. 

Maybe Obscura can confirm. I've been strongly advised against doing that by my instructor in the past - it would result in severe cost increase. I cannot confirm this is the case because I've never turned this option off myself, but I thought it ought to be mentioned.

Obscura

Yes. By turning compression off, you would end up with much higher cost (~ 3 - 4x ). But depending on the project, it might be alright. You can always track the resource sizes by looking at the statistics, and tweak them until you balanced quality/performance.