SashegDev
874b6f20c2
Основа — Horizon (MIT). История апстрима не переносится: этот репозиторий ведёт свою.
58 lines
3.2 KiB
Markdown
58 lines
3.2 KiB
Markdown
# Heightmaps
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Horizon implements the six heightmap types in the pinned Minecraft Java Edition
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**26.3**. Each map stores 256 relative column heights in padded 64-bit words.
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World-surface predicates use `isAir`; ocean-floor predicates use the version's
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`blocks_motion_in_heightmap` block tag. Motion-blocking maps also include nonempty
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fluid states, with the separate no-leaves tag for that variant.
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`HeightmapState` supplies block behavior and tag membership. `HeightmapChunk`
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supplies the vertical extent, highest occupied section and block reads. The map
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owns its packed data and checks that a supplied chunk has the same bounds. Its
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current constructor accepts positive, aligned ranges within the vanilla noise
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settings codec domain; zero-height and arbitrary runtime accessors are outside
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this bounded API.
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Updates retain the early return for blocks below the top two positions. Removing
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a qualifying surface scans downward until another qualifying block is found.
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Priming scans X, then Z, then descending Y, sharing each block read across the
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selected maps. It skips exact AIR blocks and stops a column when all selected
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maps have found a surface. If a column finds nothing, its existing value remains.
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This also applies to re-priming after a raw-data length mismatch.
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Raw imports preserve every bit when the word count matches, including padding,
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unused slots and values above the build height. Column addressing retains Java's
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wrapped `x + z * 16` calculation; invalid final indices return typed errors. The
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Rust API does not expose a mutable alias to its internal words.
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Run the differential suite with:
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```sh
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python3 tools/test_heightmap_parity.py
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```
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The [local metadata report](../benchmarks/rust-heightmap-2026-10-06/scoped-parity.json)
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records **1,671,668 matching output lines per reference JAR**, checked separately
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against the authenticated client and server. It covers all **35,723 block states**,
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all six predicate and persistence/client flags, and **100 chunk fixtures** with
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86,806 state writes, 54,306 column queries, 516 priming calls, 378 raw-data loads
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and additional update-only error cases. Selected fixtures compare exact ordered
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block reads. Cases include section and vertical bounds, leaves, fluid-bearing
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states, air variants, removal rescans, empty-column retention, packed padding,
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invalid raw lengths and wrapped column indices.
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Air/fluid facts and state identities are exported independently from each JAR and
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required to agree. These are private test inputs, not ports of block behavioral
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methods. Rust resolves heightmap tag membership using its tag loader and the
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300 bundled block-tag resources. The reference binds those resources to the
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actual vanilla block registry and invokes `Heightmap` on `ProtoChunk` instances.
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Only in-memory section storage is used; placeholder biome holders do not exercise
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biome properties or section codecs.
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Source and fixture changes during a run invalidate its report. Raw resources,
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state exports and comparison traces stay under ignored `.local`; the checked-in
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report contains metadata and hashes. CI runs this suite on its configured
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platforms; the local result does not establish those remote results. Chunk
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lifecycle integration, generated terrain, lighting and playable gameplay remain
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pending.
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