New L3 crate `lightcraft-gpu`: a wgpu device (Metal/Vulkan/DX12; none on wasm32),
WGSL kernels compiled once, buffer/dispatch/readback helpers, and a renderer that
runs the per-pixel stage (tone map, highlights/shadows, clarity/texture/sharpen,
dehaze, local mask terms, OkLCh colour ops, grading, vignette, gamut map, sRGB
encode, curves, grain) on the device. Earlier stages still run on the CPU and are
uploaded (per-stage hybrid). Stage results are cached per view next to the CPU
StageCache (new `StageCache::extension`).
The CPU pipeline stays the oracle and shares its resolved parameters with the
kernels: `finish::FinishParams` / `mask_terms`, `pipeline::plan` (stage-cache keys),
`local::plane_sigmas` / `nr_params` / `wb_matrix_for`, exact LUTs and OkLab
matrices exported for the shader prelude. Equivalence tests (skip without an
adapter): mean |d| < 0.5 LSB, max <= 3 LSB; measured max 1 LSB on Apple M4 Pro.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
The guided base, clarity band, texture band and dark channel (and the paired blurs inside the
guided filter) are independent; each alone scales poorly (subsampled grids, short rows), so they now
run under raster::par_join. Same arithmetic, identical pixels. render_bench gains a per-feature
breakdown of the per-pixel stage (ONLY=finish).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
- finish: sRGB encode through an interpolated 4096-entry table (< 2e-5 from the exact curve,
tested), exp2 instead of powf(2, x).
- guided / guided_fast: coefficient and output passes run row-parallel (were serial loops);
Image::zip_map.
- blur_bench reports process CPU time next to wall-clock (meaningful on a loaded machine).
- RENDER_CACHE_VERSION 3 (exposure-after-filters and the table change pixels by <= 2 LSB).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
3–10x faster blurs on a 3000x2400 plane (min-of-9; machine under load, see blur_bench example).
LIGHTCRAFT_PROFILE=1 now also times log-lum, base, clarity, texture, dehaze, masks and NR.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Brandon Thomas