FA-87570 / Collision detection broadphase / Member archive

Morton code puts x in the odd bits · case 05

Sort order becomes y-major, contradicting the contract and cached codes.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

solve(pts, bounds): LBVH ordering. Each centroid [id,x,y] is quantized per axis to min(1023, max(0, floor((c-lo)/(hi-lo)*1024))) (0 for a flat axis), and the 10-bit values are interleaved with x in even bits and y in odd bits. Return [[id, code]] sorted by (code, numeric id).

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 0	`[[21, 42], [11, 53312], [4, 266516], [29, 327696], [8, 349525], [19, 521559], [20, 699050], [26, 781035], [28, 804426], [24, 1043438], [3, 1046005]]`	`[[21, 21], [11, 57472], [20, 349525], [26, 513495], [4, 533032], [29, 655392], [8, 699050], [19, 785067], [28, 821637], [24, 1038301], [3, 1047290]]`	Failed

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