GI: glass and other alpha-blended surfaces show the radiance cache cell grid (squares on windows, polygons on tilted panes) #1171

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opened 2026-10-27 22:52:28 +00:00 by TheSlowly · 0 comments

TheSlowly commented

2026-10-27 22:52:28 +00:00

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Cause: a forward-lit surface has no GI pixel of its own. giForwardRefl (clean_surface_light.glsl) takes its ambient and its reflection occlusion (GI / probe irradiance) from the ONE cache cell at the fragment, unfiltered. Glass is mostly reflection, so each cell shows as its own flat tint.

Fix (in progress): read the 8 cells around the point trilinearly, and let the probes stand in for cells without an estimate. RenderVKGIForwardCacheFilter (live): 2 trilinear (default), 1 the 4 in-plane cells, 0 as before.

Related: #1052 (same look, a different cache: the ReSTIR DI occlusion cull; fixed).

With ray-traced GI on (RenderVKGI), glass and other alpha-blended surfaces show the GI radiance cache's cell grid: hard-edged blocks of different tint on a window facing a world axis, and triangles / polygons on tilted or curved panes (an observatory's dome glass). The blocks change size with RenderVKGICacheCellSize (owner A/B). **Cause:** a forward-lit surface has no GI pixel of its own. `giForwardRefl` (clean_surface_light.glsl) takes its ambient and its reflection occlusion (GI / probe irradiance) from the ONE cache cell at the fragment, unfiltered. Glass is mostly reflection, so each cell shows as its own flat tint. **Fix (in progress):** read the 8 cells around the point trilinearly, and let the probes stand in for cells without an estimate. `RenderVKGIForwardCacheFilter` (live): 2 trilinear (default), 1 the 4 in-plane cells, 0 as before. Related: #1052 (same look, a different cache: the ReSTIR DI occlusion cull; fixed).

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