I have a very simple scene.
– A flat ground that uses dynamic material instance (for trying parameters in runtime) from a standard Material. The material base Color is set to the white color. The roughness and metallic are used.
– A “T” shape on the ground with default Material
– Two spotlights and one point light.
– Everything is in a closed room.
The image here is an overview of the scene
The problem happens when I decrease the roughness of the ground plane from 1.0 to 0.0.
When the roughness is high—such as 1.0, 0.5—there is no visual problem.
However, When the roughness becomes smaller, the artifacts start to appear. Some kind of white light below the horizontal bar of the “T” shape.
The problem becomes more severe when the roughness is lower.
Nonetheless, these artifacts disappeared when I changed my camera angle so that the background is the wall—not the ground anymore.
These problems only appear when Lumen GI is enabled. I’m not sure whether it should behave in this way or not (I think it should not). I feel that the Lumen GI is running a screen-space reflection algorithm, but it should not be. My question is how I can eliminate these white lights.