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>
Brandon ThomasandClaude Opus 5.5
2dfd65b39a