Bright scenes: sky blows out to white and PBR materials wash out to grey / white #1051

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opened 2026-10-25 05:09:26 +00:00 by sky_line · 2 comments

sky_line commented

2026-10-25 05:09:26 +00:00

Owner

In a bright daytime scene the sky blows out to solid white (with heavy bloom over it), and PBR materials lose their colour and go pale grey / white. Examples: a blue PBR shirt renders light grey, and tan PBR hooves render white-grey. Blinn-Phong (legacy) parts of the same avatar (body, mane, tail) keep their colours. The ground also looks over-saturated yellow-green.

Seen on dev 1.5 (b2761279e3), RTX 5090, DLSS RR. The owner found it while testing settings. It is not GI. The owner was turning reflection probes on and off to see whether they're involved.

Likely area: the sky / environment radiance that PBR shading reads for image-based lighting (sky env, reflection probes, or their fallback when probes are off or not ready) is far too bright, or reaches tonemapping unexposed. PBR relies on that environment term much more than legacy materials, which fits the colour loss on PBR only. Related: #872 (dark PBR materials tinted blue, also suspected to be sky / probe light leaking into PBR ambient and specular).

To narrow down:

reflection probes on vs off, and probe detail;
sky preset / time of day;
tonemapper and exposure settings;
DLSS vs native.

A screenshot is in the owner's report.

In a bright daytime scene the sky blows out to solid white (with heavy bloom over it), and **PBR materials lose their colour and go pale grey / white**. Examples: a blue PBR shirt renders light grey, and tan PBR hooves render white-grey. Blinn-Phong (legacy) parts of the same avatar (body, mane, tail) keep their colours. The ground also looks over-saturated yellow-green. Seen on dev 1.5 (b2761279e3), RTX 5090, DLSS RR. The owner found it while testing settings. It is **not GI**. The owner was turning reflection probes on and off to see whether they're involved. **Likely area:** the sky / environment radiance that PBR shading reads for image-based lighting (sky env, reflection probes, or their fallback when probes are off or not ready) is far too bright, or reaches tonemapping unexposed. PBR relies on that environment term much more than legacy materials, which fits the colour loss on PBR only. Related: #872 (dark PBR materials tinted blue, also suspected to be sky / probe light leaking into PBR ambient and specular). To narrow down: - reflection probes on vs off, and probe detail; - sky preset / time of day; - tonemapper and exposure settings; - DLSS vs native. A screenshot is in the owner's report.

sky_line added the

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2026-10-25 05:09:26 +00:00

sky_line added this to the Slipstream project

2026-10-25 05:09:26 +00:00

sky_line commented

2026-10-25 05:11:04 +00:00

Author

Owner

Narrowed down with probes off at the same spot:

The sky is still blown out to white, so probes are not the cause.
PBR changes character. With probes on, the shirt and hooves are evenly washed out grey: lit by probes that captured the over-bright sky. With probes off, the shirt is dark blue again but shows bright, view-dependent sky streaks: PBR reflecting the over-bright sky directly as its fallback environment.

Conclusion: the root problem is the sky radiance itself (rendered sky + the sky term fed to lighting / IBL). The PBR washout is a symptom. Next test: DLSS vs FSR / native at the same spot, since the RR chain has its own exposure / un-expose step; then the sky preset / time of day.

Narrowed down with probes off at the same spot: - **The sky is still blown out to white**, so probes are not the cause. - PBR changes character. With probes **on**, the shirt and hooves are evenly washed out grey: lit by probes that captured the over-bright sky. With probes **off**, the shirt is dark blue again but shows bright, view-dependent sky streaks: PBR reflecting the over-bright sky directly as its fallback environment. **Conclusion:** the root problem is the sky radiance itself (rendered sky + the sky term fed to lighting / IBL). The PBR washout is a symptom. Next test: DLSS vs FSR / native at the same spot, since the RR chain has its own exposure / un-expose step; then the sky preset / time of day.

sky_line commented

2026-10-25 05:25:34 +00:00

Author

Owner

Parked for now (owner). The sky code is identical between v1.4.0 and dev, and this parcel's environment is probably set very bright, so this is likely an old behaviour rather than a regression: an over-bright sky preset (no upper clamp after srgb_to_linear, uncapped scene-gamma HDR scale, and no exposure / tonemap for legacy skies with probe ambiance 0) with our HDR bloom on top. To revisit later: whether over-bright legacy skies should go through exposure / tonemapping or a capped bloom input, instead of clamping to white.

sky_line referenced this issue

2026-10-25 05:30:19 +00:00

Device lost: GPU hang in the RT reflection trace (async compute), seen while toggling reflection probes #1049

sky_line referenced this issue from a commit

2026-10-25 21:32:16 +00:00

#872: match PBR environment specular to its diffuse ambient; prefilter the sky fallback

sky_line referenced this issue from a commit

2026-10-26 00:30:04 +00:00

#872: match PBR environment specular to its diffuse ambient; prefilter the sky fallback