Normal volume projection benchmark

Local CPU measurements for projectVolume, recorded 2026-10-08. These are synthetic Node timings, not browser frame rates or a comparison against the previous renderer.

• Hardware/runtime: Apple M3 Max, darwin arm64, Node v26.7.0.
• Workload: 256 × 256 × 256 Float32 volume (64 MiB), Fibonacci sphere of radius 80 mm, depths [-2, 2] mm, mean reduction, all samples valid, no mask.
• Each case: 2 warm-up calls, then 7 timed calls. Input construction and correctness checks are excluded; input validation, affine inversion and output allocations are included.
• The table reports median ± median absolute deviation in milliseconds. It is a local snapshot; system load and vertex ordering affect the results.
• The 164k-to-324k linear timings are noisy and consistent with cache-sensitive performance; these measurements do not establish linear time scaling. The archived bundle hash identifies the measured implementation, before later viewer fixes and legacy sampler caching.
• Correctness: every output is finite with the expected sample count; selected vertices are compared with an independent analytic field calculation. Unit tests separately cover nonlinear fields, masks, missing data and oblique transforms.
• Output arrays use 8 bytes per vertex (Float32 values and Uint32 counts). The volume buffer is borrowed.

Vertices	Samples	Nearest (ms)	Linear (ms)
32,492	5	14.5 ± 2.2	21.7 ± 2.5
32,492	16	26.9 ± 1.1	52.5 ± 3.7
163,842	5	58.5 ± 9.3	85.6 ± 2.9
163,842	16	109.6 ± 6.2	263.0 ± 33.5
324,002	5	94.0 ± 3.1	264.4 ± 42.9
324,002	16	325.9 ± 75.7	508.2 ± 4.2

Larger cases take hundreds of milliseconds synchronously. Project once and reuse the scalar values for display changes; applications needing uninterrupted interaction during repeated projection can run the function in a worker.

Reproduce

npm run build
node scripts/benchmark-volume-projection.mjs --output=/tmp/volume-projection.json

The repository retains full measurements, variability and the exact built ESM SHA-256 in benchmarks/volume-projection.json. No timing threshold is imposed on CI.

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