Draft: Refraction fog based on water depth (!2922) · Merge requests · OpenMW / openmw

Qlonever requested to merge qlonvirniriy/depth-refraction:master into master Apr 12, 2023

Similar to a merge request made by wareya !672 (merged) two years ago, but using different math to mitigate the issues people had with it.

The way the water shader currently handles refraction fog isn't very realistic. How visible an object is through water should be based on the amount of water between it and the camera, not just its distance from the camera. With the current refraction fog calculation, water turns completely opaque if the player moves too far away from it. This looks bad, and it's especially jarring if the player clears the visibility threshold quickly, as they might when falling or using jump spells. This MR changes the shader to calculate refraction fog based on water depth, using a curve instead of a linear fade to keep it from looking too transparent.

Changes:

water.frag

depthSampleDistorted and waterDepthDistorted are calculated after screenCoordsOffset is modified, fixing an issue where refraction fog would be misaligned when there was a sharp change in depth
screenCoordsOffset is modified twice to further reduce shore artifacts
waterDepthDistorted is interpolated with realWaterDepth to prevent splotchy coloring at shores
Refraction fog is calculated using waterDepthDistorted instead of depthSampleDistorted

water.cpp

To prevent shore artifacts at greater distances, the offset of reflection/refraction cull planes scales based on the camera's distance from the water plane and the current FOV setting

Notes:

This MR lessens the problem in #7036, but doesn't fix it completely. To fix that issue, something else needs to be done with the way reflection/refraction textures are culled, since they don't perfectly align with the actual edge of the water.

Screenshots:

Before: