How do I get rid of these dark spots on my lightmap?

Hello helpful Unreal Experts!

I am having some issues baking lightmaps for some rocks in my scene. Whenever I bake the lighting, I get dark spots on the rock. The spots don’t appear at seams in the lightmap, just in places where small shadows should occur. Instead of small shadows, though, I get deep black splotches. I have some pictures to illustrate the issue.

Rock with no baked lighting:

Rock with baked lighting (example splotch in the middle):

Rock lightmap UVs:

I suppose that the polygons are just too small for the lightmap, but I’m not sure how to fix that. Should I cut my rock into several different shells to get nice lighting, or would it be better to have something more contiguous, like what I have already?

Have you tried increasing the lightmap resolution in the static mesh settings? This can be done in the content manager or you can override it in the view port on a per object basis.

If this does not help I would say it is to do with the way you have unwrapped the UV’s. Do you receive an overlapping UVs warning after you bake the lighting?

Have you tried to increase the “indirect Lighting” in a global post processing volume, its under the global illumination property tab?

You can also increase the Indirect Lighting intensity in the “Light” properties panel of the light you have in the scene.

Also if you do not have a light mass importance volume covering the area you are trying to bake the lighting at, creating one will help a lot.

From the look of it the UV’s seem to be the most likely problem, but try the things I have listed and let me know.

Hi Ategig, thanks for the response.

Increasing the lightmap resolution results in slightly different splotches, but it does not make them go away.

I don’t get any warnings about overlapping UVs when I bake the lighting, but the meshes are just decimated versions of the rock sculpts, so there are a few long, narrow triangles that I worry are causing the problems. It’s also possible that it’s a problem of only having one light in the scene (the sun) and small overhangs in the rocks. Perhaps I am getting an accurate lightmap, and it’s just ugly.

The idea behind the baking is that the bounce lights eliminate the need for fill lights, right? Should I just be patient and wait until I have more rocks together, along with a floor? Will the bounce light then lighten up the shadows? Is there some other way to get softer, more natural shading?

Hey Ategig,

Both of those changes increased the GI contribution of the light, leading to lighter shadows. I also tried creating a bit more of an environment around the rock, to actually give the light something to bounce from, and that had a great impact on the shadows as well. There are still a few dark splotches that show up here and there – I think you’re right that the UVs are responsible – but they are generally small, and probably (hopefully) won’t be noticed once I add some dappled light shadows from foliage.

Thanks a lot for your help, and for responding so quickly!