UE 5.8, Windows, DX12, TSR.
I have a sandstorm built as a VolumetricCloud layer on a small planet (radius 250 km). The layer floor sits 10 m above the sand, so the player walks inside the cloud during a storm — it is a haboob, the wall has to touch the ground.
Symptom. Anything that moves leaves a trail: the character, the vehicle, and also the whole scene when only the camera rotates. The trail is visible only against the lit dust, never against dark terrain, and only while the player is inside the storm’s dust. Outside the storm, even against a bright sky, there is no trail.
What I measured (each test from a freshly launched editor, one change at a time):
| test | result |
|---|---|
r.SSR.Quality 0 |
no change |
r.AntiAliasingMethod 0 |
trails gone (unusable — aliasing + black flicker around the character) |
r.TSR.Velocity.HoleFill 0 |
no change |
r.TSR.ShadingRejection.SampleCount 4 |
no change |
r.TSR.History.ScreenPercentage 200 |
no change (already 200 from Scalability) |
r.VolumetricFog.HistoryWeight 0.5 |
no change |
r.VolumetricFog.TemporalReprojection 0 |
no change |
r.VolumetricRenderTarget 1 (+ ini Mode=2) |
trails gone, but heavy square blocks of dust |
r.VolumetricRenderTarget 1 + Mode 0 |
worse |
r.VolumetricRenderTarget 1 + Mode 3 |
trails stay, concentric banding stays, GPU 15.2 ms |
r.VolumetricRenderTarget 0 (current) |
no blocks, but trails + concentric banding |
| Standalone Game instead of PIE | trails are there too |
r.TSR.Visualize 0 shows the dust area uniformly green with no red at all — TSR accepts the history there and rejects essentially nothing.
Ghosting against the lit dust:
I also tried removing the cloud’s near-field “haze” term from my own material (a separate additive component, independent of the wall): no change. So it is the dense wall itself, right in front of the camera.
My reading. A VolumetricCloud writes neither depth nor velocity, so TSR has nothing to reject history on, and with r.VolumetricRenderTarget=0 the layer goes through TSR instead of being composited after it. With =1 it is composited after TSR (trails gone) but the reduced-resolution buffer shows as square blocks, because the player is inside the volume and dense matter sits in the near field — which is exactly where that reduction stops being invisible.
Questions:
- Is there a supported way to make TSR reject history over a VolumetricCloud (anything that gives it depth or velocity for the cloud)?
- With
r.VolumetricRenderTarget=1, is there a way to stop the reduced-resolution blocks when the camera is inside the cloud layer, other than full-resolution tracing? - Separately: the concentric banding centred on the camera gets denser when I raise
View Sample Count Scale(0.55 → 1.2), so it is the ray-march step boundaries. Is there a jitter/dither for the cloud march that works withr.VolumetricRenderTarget=0?
Any pointer appreciated — including “a cloud is not the right tool for a volume the player stands in”, if that is the answer.