Commit 2c000cb72f changed the interpolation limits from (0.04, 1.0) to (0.04, 0.37). This is incorrect, as we want to have an F0 of 0.04 for dielectrics (materials with metalness of 0.0) and an F0 of 1.0 for metals.
The Schlick approximation uses an F0 of 0.04 for all dielectrics and it's good enough.
Having it lower than 1.0 leads to an incorrect application of the Fresnel effect for metals and leads to bugs like #79549
In a test scene with mixed rough and non-rough materials, this saves
upwards of 0.15 ms of GPU time with very little visual artifacting
(GTX 1080, 2560×1440).
- Fade reflection towards inner margin and clip it at screen edges
instead of external margin.
- Round edges of the fade margin if both are being cut off to prevent
sharp corners.
Co-authored-by: puchik <puchik@users.noreply.github.com>
