And I believe they’re jittery because of how GPU particles do collision. Since GPU particles can only collide against the depth buffer, and TAA jitters the depth buffer, so does the collision for GPU particles.
Unreal’s default anti-aliasing technique, temporal anti-aliasing. They might call it Temporal Super Sampling, or Temporal Super Sampled Anti-Aliasing … I forget what people are calling it at this point.
It works by shifting the camera’s position slightly every frame then averaging the results. That’s greatly simplifying it, but the result is the depth buffer moves every frame in a kind of noisy jiggle.
I think they may have just recently implemented shadows for GPU particles, because when I turn on “Cast_Translucent_Shadow” for the light I see big blocky shadows appear.
The shadow map resolution is terrible but at least it appears they turned on.