FA-51784 / Raster clipping / Member archive

Guard band triangle clip: bbox left unclamped · case 04

Guard-band triangles report bounding boxes starting left of the viewport.

Member previewVariant 4 · 3 implementations · 13 checks per implementation

Case contract

Each command is a triangle of three exact vertices in continuous raster coordinates. The viewport is [0,size]x[0,size] and the guard band extends one viewport size beyond each side. A triangle is rejected when all vertices lie strictly beyond the same viewport edge; accepted when all vertices are inside the closed viewport; guard-banded when all vertices are inside the closed guard band; otherwise it requires geometric clipping. Accepted and guard-banded triangles report the pixel bounding box [floor(min x),floor(min y),ceil(max x),ceil(max y)) clamped to the viewport, or None if empty.

Why this case matters

Raster clipping decides which pixels a primitive may touch; a single wrong clip decision writes outside the target or scissor, or silently drops visible coverage.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
explicit case 7	`[["guard", [-8, 1, 2, 3]]]`	`[["guard", [0, 1, 2, 3]]]`	Failed

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