FA-86522 / Procedural level generation constraints / Member archive

Chunk seed derivation: Large world seeds are not reduced · case 02

Seeds above 32 bits produce different chunk ids than the save format stores.

Member previewVariant 2 · 3 implementations · 8 checks per implementation

Case contract

Coordinates are zigzag encoded (v >= 0 -> 2v, v < 0 -> -2v-1). seed = (world_seed*1000003 mod 2^32) xor (zz(cx)*73856093 mod 2^32) xor (zz(cy)*19349663 mod 2^32). The generator state is seed, or 1 when seed is 0, advanced by three 32-bit xorshift rounds (<<13, >>17, <<5, each left shift masked to 32 bits). Returns [seed, state % 100].

Why this case matters

Procedural generators silently emit unplayable or unfair levels when a single constraint check uses the wrong boundary, axis, neighborhood or update order; the defect is visible in exact generated geometry.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
fault site world seed mask #1	`[1099514929939402134, 31]`	`[3628518806, 87]`	Failed

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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