RT sun shadows fuzzy and swimming under DLSS when sun and projector shadows are traced separately #1050

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opened 2026-10-25 05:07:04 +00:00 by sky_line · 1 comment

sky_line commented

2026-10-25 05:07:04 +00:00

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With "Trace sun and projector shadows together" off (the separate sun-shadow path), static RT shadows (tree shadows) look fuzzier and vibrate in place.

When it happens (owner's A/B):

DLSS Ultra Performance: strong.
DLAA: some movement.
Native, and FSR: none.
With merged tracing on, it doesn't happen.

Likely cause: how the separate sun-shadow mask feeds DLSS Ray Reconstruction. Under RR, some RT signals are routed raw (#870 raw signal routing, RenderVKDlssRawSignals). The merged path goes through our denoiser first, but the separate sun mask probably reaches RR raw and jittered, and at very low render scales RR can't stabilise it. FSR never takes raw signals, which fits FSR being clean.

Done when: separate-path sun shadows are as stable under DLSS / DLAA as with merged tracing or FSR.

With **"Trace sun and projector shadows together" off** (the separate sun-shadow path), static RT shadows (tree shadows) look fuzzier and vibrate in place. **When it happens (owner's A/B):** - **DLSS Ultra Performance:** strong. - **DLAA:** some movement. - **Native, and FSR:** none. - With merged tracing on, it doesn't happen. **Likely cause:** how the separate sun-shadow mask feeds DLSS Ray Reconstruction. Under RR, some RT signals are routed raw (#870 raw signal routing, RenderVKDlssRawSignals). The merged path goes through our denoiser first, but the separate sun mask probably reaches RR raw and jittered, and at very low render scales RR can't stabilise it. FSR never takes raw signals, which fits FSR being clean. **Done when:** separate-path sun shadows are as stable under DLSS / DLAA as with merged tracing or FSR.

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2026-10-25 05:07:04 +00:00

sky_line added this to the Slipstream project

2026-10-25 05:07:04 +00:00

sky_line referenced this issue from a commit

2026-10-25 06:21:59 +00:00

#1050: RT shadow mask stabilises its own sun under DLSS Ray Reconstruction

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