1: reflection
Create black floor and chrome ball in my scene.
but reflection is not correct I think.
How to fix it ?
2: skylight
How to rotate skylight(hdri) at runtime ?
Reflections capture surfaces with roughness at 1 to avoid directional artifacts. In cases like this it stands out but generally it solves more issues.
You could set speculate to 0 or just lower on the black floor.
Thank you RyanB.