Question about lightmap seams

Hey so I pretty much asked this question in another question, but since I didn’t get any replies I thought I would try again with a clearer example.

Basically I want to know why I’m getting these seems once I bake the lighting of these two walls. I want to build some modular kits and I don’t want to run into this problem because in order to build the kit I would have to make pieces with seamlessly “snap” onto each other, and this is going to be a problem.

In the example I’m using the same mesh for all the walls. It’s just a 200 by 200 cm plane with UVs taking up the entire space.

Much appreciated for any insight you guys can give me!

Hi Johna,

You will likely notice these seams with any assets that have planar faces that are aligned together due to the way indirect lighting is calculated in UE4. It’s a known artifact that isn’t a simple 1, 2, 3, fix. And while this is a known issue, it’s not likely to be resolved in the near future.

However, you can have a look at this thread on the forums for some ways to get better results: Modular Asset Lighting Problem - Rendering - Unreal Engine Forums

So to go over some of the key points:

  • This is an issue withe static indirect lighting (GI).
  • Each asset is handled on a different thread when being calculated so this is why you get the seam

You can reduce these artifacts by doing the following:

  • Snap the Lightmap UV hard edges to a correctly scaled grid for your target texture resolution
  • Use larger wall piece rather than over using modular design
  • Use other geometry to mask the edge seams

Thank you!

Tim