Strange Shadow problem

Hello there!
I’m building a huge tank from japan, made to contain floods. I made a very low res catwalk and instanced a light tube over it. I added a few decals on the wall. Now, when I bake the lightmaps, I get strange shadows on a few spots, on both the right side of the room and the left side, as there is a catwalk on both. In the beginning, I thought It came from the decals, as the size of the decal bounding box could have occluded the light on those problematic areas. But after removing the decals and re-baked the lights several times, the problem is still here.
Of course the light tubes don’t cast shadows and the lights I’m using (other that the emissive geometry of the tube light) are 2 rectangular lights, pointing in opposite directions.

Any idea?
Thank you

Are the lights positioned correctly? The pivot point needs to be inside the corridor.

You mean the rectangular lights? Yes, they are, and all of them in the exact same location. Same goes for the “object” tube light. I moved the ones in the problematic area slightly more inside the corridor but, same thing. Is It possible that the decals created that shadow artifact and that, for any reason (bug?) Even though I deleted them, baking the lightmap still takes them into account in the original position?

Once you’ve removed them and baked again, it should be ok. I’m not sure why you’re getting these artifacts. You might try repositiong the mesh, or in the worst case, copy paste everything into a new map.

So, I replaced the whole catwalk with new geometry, (1 piece instanced all along the walls) , still the shadows are in the same place. It only appears after baking, if I turn all those light to movable, shadows are gone.

I’m running out of ideas here. Have you tried it with a different mesh?

Are the lightmap channels setup correctly?

Thank you for your help, much appreciated. I spent the last day replacing the rectangle lights by omnis, inspecting the geo, replacing parts that could be involved (close to the shadows) turning cast shadows off for all lights… no change. I come to wonder if there is a way to open and edit the lightmaps say in photoshop and copy - paste an “healthy” part of the catwalk onto the faulty ones. Not sure where to find those lightmaps and how to open them with PS.
I’m far from being a expert with unreal but I have 20 years of experience in the 3d field and I became rather methodical when It comes to diagnose and find a solution. Here, except some kind of a bug, I don’t have any clue on what’s left to search for.

You stand a much better change of editing the lightmaps in Blender.

You can also see the lightmaps in UE, of course. And it will probably be immediately apparent if there’s a problem.

If you can condense if to a very small scene and make small project, I could take a look.

BTW: It really helps to quote, otherwise there is no notification :slight_smile:

I’m struggling a lot during these days about lighting in UnrealEngine. Basically I think it is a problem about baked lights. Check your LPV and rebuild the light.
Otherwise it could be about geometry

Since UE4.25 has an improvement in direct GI I prefer to use this method that of course in CGi in the defnitve one. But it cost in terms of performance.

Ok, I’m rebuilding the whole project in unreal 4.25, which has already It’s own problems, like not accessing my server and making me work from a local disk. Anyway, I found a few things and I will post later today or tomorrow, maybe a short video to be more specific in my explanations.
Thank you for the tip on quoting, i wasn’t aware of It.

Ok, cool :slight_smile: