fix(worldgen): shuffle which biomes a multi-biome world uses, not just how many - #697
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…t how many (#696) ResolveBiomes rolled only the biome COUNT (2..pool) and then always took the first N pool entries, so the tail entries of a type's biome pool in data/planets.json were missing from every world that rolled a smaller count, and the first entry appeared on every world of the type. A per-world Fisher-Yates shuffle (seeded from PlanetSeed, so server and client preview agree) now also picks WHICH entries make the cut. ResolveBiomes/BiomeResolved became internal (+InternalsVisibleTo for the test project); two new tests cover membership variety across seeds and determinism. Only newly generated chunks are affected. closes #696 Co-Authored-By: Claude Fable 5 <[email protected]>
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Summary
ResolveBiomesrandomised only the biome count (2..pool, seed-derived) and then always took the first N entries of the planet type''s biome pool indata/planets.jsonorder. The doc comment promised "so each multi-biome world differs", but worlds only differed in pool depth, never in selection: a 2-biomevariedworld was always sand+grass, and a tail entry could never appear without all the entries before it.This PR adds a per-world Fisher-Yates shuffle over the pool (seeded from
PlanetSeed, so it stays deterministic and server + client preview agree) before the firstcountentries are taken — which biomes a world gets now varies as well as how many.ResolveBiomesandBiomeResolvedbecameinternal, withInternalsVisibleTofor the test project, so the selection logic is testable without generating chunks.Compatibility
Only newly generated chunks are affected. On existing worlds, terrain generated after this change may use a different biome set than neighbouring already-persisted chunks — same class of change as the beaches/landforms releases.
Test plan
dotnet test -c Release --filter Category!=Slow— 1377 server + 147 client green locallycloses #696
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