r_FogDepthTest

Enables per-pixel culling for deferred volumetric fog pass.
Fog computations for all pixels closer than a given depth value will be skipped.
Usage: r_FogDepthTest z with...
  z = 0, culling disabled
  z > 0, fixed linear world space culling depth
  z < 0, optimal culling depth will be computed automatically based on camera direction and fog settings