- handle heightFalloff=0 (i.e. fog doesn't depend on height) correctly,
previously, a divide-by-zero on the cpu side would get in the way.
The fix is to clamp heightFalloff to a small-enough value, and to
make sure that this is handled correctly in the shader.
- default fog distance is 0 instead of 1m
- inScatteringSize parameter should be allowed to be large in samples
cb356606d9