GI hits: diffuse-only probe lookup (the probe walk runs at 68% of hits) #982

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opened 2026-10-23 18:07:42 +00:00 by sky_line · 0 comments

sky_line commented

2026-10-23 18:07:42 +00:00

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The radiance cache finds only about 32% of GI hit lookups, so the probe walk runs at the other ~68%. sampleProbesEx fetches irradiance plus two radiance samples along R, which a diffuse bounce barely needs. The cache-hit path already uses rad = irr; applying the same rule on the probe path would save about 0.3-0.8 ms.

Visual: metals and gloss at GI hits lose their reflection in bounced light. Small effort.

From the 2026-10-23 GI performance pass. Baseline: RTX 5090, 4K, DLSS Ultra Performance (1280x720 render), GI at full render resolution, GI 3 + cache, ReSTIR DI 3, emissive on: GPU 30.9 ms/frame (GPU-bound), async deferred lighting 20.1 ms, `c_gi_trace` 12.7 ms (883k rays/frame). The radiance cache finds only about 32% of GI hit lookups, so the probe walk runs at the other ~68%. `sampleProbesEx` fetches irradiance plus two radiance samples along R, which a diffuse bounce barely needs. The cache-hit path already uses rad = irr; applying the same rule on the probe path would save about 0.3-0.8 ms. Visual: metals and gloss at GI hits lose their reflection in bounced light. Small effort.

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sky_line added this to the Slipstream project

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sky_line self-assigned this

2026-10-26 02:58:24 +00:00