Self-reflection is visible in metallic materials with VoxelGI due to bias being too low

[jcostello]

Godot version

v4.0.dev.calinou [b4cea10]

System information

Mx Linux (Debian Based)

Issue description

When baking VoxelGI in a metalic sphere there is self reflect

Steps to reproduce

Use the main.tscn in the Minimal reproduction project

Minimal reproduction project

Voxel.zip

[Calinou]

Related to #50842.

This is because the Bias/Normal Bias properties are set to values that are too low for this particular scene. Try playing around with those values.

For the record, this also happens with GIProbe in 3.x.

[jcostello]

@Calinou yeah playing with it helps but distorts the rest of the lighting in a complex scene. I could't find a good setup that does't messed up the rest of the lighting. Maybe creating the voxel a bit smaller than the object?

[Calinou]

If avoiding self-reflections entirely in master is your priority, I've found that using a Bias of 0 and Normal Bias of 1.75 works decently: #52115 (comment)

In 3.x, keeping the default Bias but setting Normal Bias to 0.1 or greater seems to work better.

It will result in flatter-looking indirect lighting in some areas, but it's not something that can be prevented without the use of expensive anisotropy.