Fix Sobol sampler and D65 illuminant for Metal GPU backend#38
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jkrumbiegel wants to merge 3 commits intoJuliaGraphics:masterfrom
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Fix Sobol sampler and D65 illuminant for Metal GPU backend#38jkrumbiegel wants to merge 3 commits intoJuliaGraphics:masterfrom
jkrumbiegel wants to merge 3 commits intoJuliaGraphics:masterfrom
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Two issues fixed: 1. Runtime NTuple indexing returns 0 on Metal. Replace PERMUTATIONS_4WAY (nested NTuples indexed at runtime) with PACKED_PERMUTATIONS_4WAY (bit-packed UInt32 values appended to the Sobol matrices GPU array). lookup_permutation now takes the matrices array and uses bit shifts. 2. @nexprs unrolled loops cause Metal compiler crashes or miscompilation when the loop body references non-constant kernel arguments. Replace with regular for loops in sobol_sample. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
The D65 illuminant spectrum was stored as NTuple{107, Float32} and indexed
at runtime, which returns 0 on Metal (same root cause as the Sobol fix).
Add d65_values field to RGBToSpectrumTable as a GPU array, and add
GPU-compatible sample_d65/sample_d65_spectral overloads that read from
the array instead of the NTuple constant.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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great!
would you mind sharing the code for all these? It would be nice to test and show the output across all backends, so starting with a set of references as in Makie make sense. |
Author
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The 20 materials test scene is in RayMakie in |
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Summary
PERMUTATIONS_4WAY(nested NTuples) with bit-packedUInt32values appended to the Sobol matrices GPU array. Also replace@nexprsunrolled loops with regularforloops (the unrolled form causes Metal compiler crashes or miscompilation with non-constant kernel arguments).NTuple{107, Float32}indexed at runtime. Addd65_valuesfield toRGBToSpectrumTableas a GPU array, with GPU-compatiblesample_d65overloads.How these changes were tested
Created with the help of Claude Code