Sky-view lookup table for sky / haze #819

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opened 2026-10-17 18:10:01 +00:00 by sky_line · 1 comment

sky_line commented

2026-10-17 18:10:01 +00:00

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Context: measured on a GTX 1080 (Pascal) at 4K with the test-control channel and the shader clock (RenderVKShaderClockLighting) / pipeline stats (RenderVKPipelineStats). The frame is GPU-bound but not bandwidth-bound (memory controller ~36% busy on the 1080, ~14% on a 5090): it is latency / occupancy bound, so trading a little memory traffic for fewer registers and fewer dependent loads should help every GPU generation.

skyColor (~6 exp, a pow, 2 sqrt, sRGB conversion) depends on direction only; a per-frame sky-view table parameterised around the sun could serve the fade target, probe-miss sky, water reflection and the sky pass. Only pays if the atmosphere cost is ALU rather than load latency: decide after the atmosphere-constants ticket's measurement. Context: measured on a GTX 1080 (Pascal) at 4K with the test-control channel and the shader clock (RenderVKShaderClockLighting) / pipeline stats (RenderVKPipelineStats). The frame is GPU-bound but not bandwidth-bound (memory controller ~36% busy on the 1080, ~14% on a 5090): it is latency / occupancy bound, so trading a little memory traffic for fewer registers and fewer dependent loads should help every GPU generation.

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2026-10-17 18:10:01 +00:00

sky_line added this to the Slipstream project

2026-10-17 18:10:01 +00:00

sky_line referenced this issue from a commit

2026-10-22 19:32:55 +00:00

#819: sky-view lookup table for the haze sky (RenderVKSkyLUT, default off)