Another feature update for translucency in 5.1:
Translucency Compliance in GPULM 5.1
GPULM had limited support for translucency because of perfomance limits. The only translucency model it supports is Thin Translucent. Yet it seems like a lot of people do like CPULM behavior for translucent shadows. Thus in 5.1 GPULM supports translucency as follows.
When the shading model is Default Lit and blend mode is translucent, GPULM behaves like CPULM to cast colored shadows (from static lights). Internally this is actually emulated by a Thin Translucent model with parameters Opacity = 0, TransmittanceColor = lerp(1, BaseColor, OriginalOpacity). When the shading model is indeed Thin Translucent, GPULM behaves like the path tracer and uses the parameters the path tracer uses.
Note that GPULM does not support any open, single sided geometry. They are treated as invalid and GPULM uses them to remove invalid samples inside geometry (like, around the corners of two walls intersecting). Any single piece geometry should either be marked as two sided or with the front face facing the scene (like, you are baking an interior and the window glasses can be single sided with the front side facing the inside). When the requirement is not met expect certain features especially FBRG to break (grid patterns):
