The source is uploaded once per view (kept with the GPU stages) and resampled on
the device: orientation as an integer pixel map, the Mitchell area prefilter
with the CPU's exact taps, then one bilinear resample through the
crop/straighten/flip affine or through the full warp (inverse perspective,
manual distortion, embedded DNG WarpRectilinear per plane, lateral CA, manual
and embedded vignetting gain, blank outside the source). `Frame::sample_plan`
(new) decides prefilter size and mode for both renderers; sources larger than
the device's buffer limit are still resampled on the CPU.
Equivalence: all 8 orientations with and without crop/straighten/flip, embedded
lens + perspective: max 1 LSB.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Linear and radial gradients, luminance and colour ranges and brush strokes are
evaluated by a WGSL kernel per component, combined (add/subtract/intersect,
component and mask invert, amount) into one device buffer of alpha planes that
the per-pixel stage reads directly. Brushes use the CPU's dabs
(`masks::brush_dabs`, shared with the rasterizer) and the closed form of the
flow accumulation (1 − Π(1 − a·flow), capped at density). Sky / Subject /
Background and other heuristic shapes, and brushes of more than 4096 dabs, are
evaluated on the CPU inside the same render and uploaded.
New equivalence case with CPU-evaluated shapes, subtract/intersect and amount;
all cases stay at max 1 LSB.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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>
Brandon Thomas