Vulkan: GIProbe Reflection does not take sky into account

[NHodgesVFX]

Godot version: Godot 3.2 Beta 5, Godot 4 Vulkan OS/device including version: Windows 10 64 bit Issue description: When using GIProbe the sky is not taken into account in reflections. This is most visible in metallic chrome surfaces.

Godot 3.2 Beta 5

Godot 4

Steps to reproduce: Add a plane to the scene, add a sphere with a chrome material, and add a GIProbe and bake. Minimal reproduction project: GIProbeSkyReflections.zip

[akien-mga]

That's by design AFAIK, GIProbes are meant for interior scenes, they only take into account what is included in their gizmo. The bigger the gizmo, the more computationally intensive the calculations will be.

I'm not an expert on GIProbes though, so might be worth getting a confirmation from @reduz.

[clayjohn]

@akien-mga when the interior flag is false sky contribution should be used.

[clayjohn]

I can confirm this behaviour. However, I am uncertain whether it is a bug or a limitation in the implementation of GI Probes. I will take a look into it, but I think chances are this is something that won't be fixed for 3.2. 4.0 comes with an entirely new implementation of GI Probes.

Edit: Currently, this is just a limitation of the implementation. Right now sky contribution is not baked into the GIProbe data. It is mixed in at draw time. This means we get accurate sky contributions on primary light bounces, but on secondary bounces, we get no sky contribution. The only way to improve this behaviour would be to rewrite both the baking of the GI Probes and reading from them. Because of how core these changes will be. I will mark it for 4.0.

[KoBeWi]

Was this fixed already in 4.0-dev?

[Calinou]

I can reproduce still this in 4.0.rc2 (the floor in the reflection should appear purple-ish, not gray):

Minimal reproduction project (4.0): VoxelGISkyReflections.zip