Canvas watercolor wet-paint lab
Generate three synchronized grid swatches: dry paper, wet-on-wet, and late-water backrun. This is an artistic approximation with bounded work, not physical watercolor or spectral pigment matching.
Model boundary
- Paper height, water, suspended pigment, and deposited pigment are separate bounded fields.
- Flow is double-buffered and capped by source water; every cell must remain finite and nonnegative.
- The numeric receipt hash excludes Canvas pixels because browser color and PNG bytes can vary.
- Maximum grid is 96 × 54, maximum 240 steps, three fixed pigment channels, no files, network, storage, or user code.