Lighmass bakes behave differently depending on camera position while baking.

[lukinu_u]

For my project, I’m baking with Lighmass on Unreal Engine 5.0.3 (non-negociable, as certain part of the project depend on said version), and I’m facing a very weird issue.

When the bake is completed, certains meshes will have incoherant lighting with small or big portion of much lighter area that don’t match the scene.

Here are a few examples :

On the following picture, you can clearly see that certain meshes take the correct light (the darker ones) while many other simply ignored the “correct” light and baked much lighter.

As mentioned earlier, the bake behave differently depending on if the mesh is within the camera during the bake or not. Here is a comparison of the same angle with “regular” bake (first picture) and a bake while the camera is facing at them (second picture).

For now the temporary fix has been to move around the entire level during the bake to ensure everything was visible on screen and prevent artifacts, but it’s realistically not a good workflow, and is not reliable at all.

[lukinu_u]

I fixed the issue.

For practial reason we did split multiple component of the game in different persistant sub-levels to work on them separately (hitboxes, lights, map visual, etc). We assumed it would be the exact same as one level if they are all persistant and loaded from the start but it caused some issue.

In this particular case, the meshes being in a different level than the lights broke the bake and caused the issue mentioned in the post.

TLDR : Keep the meshes in the same level (or sub-level) as the lights and you won’t have the baking errors.