FA-87370 / Collision detection broadphase / Member archive

Grid cell index truncates toward zero for negative coordinates · case 05

Boxes straddling the origin share cell 0 with boxes one cell away.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

solve(boxes, cs): insert each box [id,minx,miny,maxx,maxy] into every grid cell floor(min/cs)..floor(max/cs) inclusive on both axes. Return [sorted unique canonical candidate pairs sharing a cell, total cell insertions, largest bucket size].

Why this case matters

Broadphase stages decide which object pairs ever reach narrowphase; a wrong boundary, ordering or bookkeeping rule silently drops real contacts or floods the solver with false candidates.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
case 1	`[[[5, 31], [5, 32], [5, 33], [31, 32], [31, 33], [32, 33]], 26, 4]`	`[[[5, 31], [5, 32], [5, 33], [31, 32], [31, 33], [32, 33]], 29, 4]`	Failed

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