Vulkan: Importing 3D scene with Static Lightmaps disables automatic LOD

[Calinou]

Godot version

4.0.dev (94ce83b)

System information

Fedora 34, GeForce GTX 1080 (NVIDIA 470.74)

Issue description

Importing a 3D scene with Static Lightmaps disables automatic LOD without warning the user, which can harm performance unexpectedly. This occurs even if LightmapGI isn't used in the scene and no lightmaps are baked.

Ideally, we should see if we can lift this limitation as it'll make lightmapping more usable in larger scenes. If we can't lift this limitation, we should document it somewhere. Adding descriptions to specific import settings is not supported yet, so I guess we'll need to add a note in the Importing 3D scenes and Baked lightmaps documentation pages.

Screenshot with wireframe mode:

• Left: Static Lightmaps (so detailed it looks like non-wireframe mode)
• Right: Static

Steps to reproduce

• Import mesh with the lightmap option set to Static Lightmaps.

Minimal reproduction project

test_auto_lod.zip

[Calinou]

This was confirmed by @JFonS on the Godot contributors chat. He said that UV2 transfer can be implemented in LOD generation, but it won't always look good in all situations (it may cause visible leaks). It's worth trying nonetheless 🙂