Since upgrading to 5.6 with VSM, blocky artifacts have become extremely noticeable (see attached image).
Often, spotlights are used to fake pools of sunlight, requiring them to be placed at a far distance, with large attenuation radius’ and narrow cone angles. This includes Source Radius also causing artefacts, with soft penumbra (soft) shadows being completely gone. Unreal 5.4 appeared to be ok from memory.
Work-around hack (not good for performance)
Rect. Lights with barn doors, or Directional Lights with material function mask (faking a spot cone), both seem to retain their correct penumbras (relative to source angles) with good visual results, without blocky artifacts, but without the spotlight’s cone angle culling, these light types are more expensive with light overlap and complexities.
Is there a fix, cvar change, or a better work-around to fake optimized pools of soft light in a game?
thanks for the repro steps. I have checked the public issue tracker and it seems that this is a [known issue in 5.4, 5.5 and [Content removed] with a target fix coming up in 5.7: https://issues.unrealengine.com/issue/UE-290280
If you need to work around it on 5.6, in addition to the other workarounds you’ve already mentioned, you can try enabling Distance Field Shadows or Cast Ray Traced Shadows in the spotlight settings, although the latter may have a significant performance impact.
There’s still the obvious issue of blocky shadows for extremely wide Outter Cone Angle values, but that’s always been a known issue that artists have worked around. See below for Outter Cone angle at ~73 FOV: