ARC INK

Recorded arcs draw as true circles evaluated per pixel on the GPU. These cases draw them on a transparent stage and grade every device pixel against a reference that knows nothing of the shader: the distance to each arc in double precision from its centre, radius and sweep, feathered the way the stroke is, composited. A dropped arc, a strip that stops short of a cap, a sub-pixel dot that never made it, or a radius the size of a continent that single precision misplaced all show as pixels one side inked and the other did not. Beneath each stage: the GPU alpha, the reference and their difference, magnified.

Holds

no dropped or invented pixels · worst pixel under 32/255 (an eighth of a pixel) · mean under 0.25/255 · total ink within 1%

Fixtures

Pennington County parcels and sales-tax jurisdictions with recorded curves (JSON-FG)

Drives

e2e/arc-ink.spec.ts, through window.__renderCase(id)