beezm
a7e6c17422
Byte-accurate v2 contract (magic/version, tagged sections, registered FourCC table, validation rules, re-encode sentinels, extension path) plus the v1 legacy summary — v1 stays live per the safety-net plan. READMEs updated additively: parser dispatch, dual-write outputs, harness usage, server params cross-check, wire-format hazard rewording (u8 on v2 path, range-checked; append-only rule unchanged). Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
65 lines
4.3 KiB
Markdown
65 lines
4.3 KiB
Markdown
# Core Module
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Shared, stateless logic used by both the server and client paths: the `.dat` parser, the mesher, the
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voxel data containers, and the material lookups. **No Godot nodes, no scene state.** These scripts
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define what things are and how to calculate them; they never remember what is currently happening.
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## Components
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### `MapDataParser.cs` — the data bridge
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Deserializes the binary `.dat` blueprint written by `/Tools` into a `WorldBlueprint` held in RAM:
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map size, the float heightmap, the biome map, town locations, **all four tiers** of A\* road
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vectors (Highways, Branch Roads, Rugged Roads, Trails), and — from v2 files — the embedded
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generation params (seed, sizes, impact centre, provenance) and each town's highway-node flag.
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**Two formats are live** (byte-accurate contract: `Core/Scripts/BLUEPRINT_FORMAT.md`). The parser
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dispatches on the file's first byte:
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- **v2 (primary)** — raw `ISLA` magic, u32 version gate, then tagged sections
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`[u32 tag][u64 length][payload]`. Unknown tags are skipped by length, so future sections are
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invisible to older readers. Validated on read: version, MapSize bounds, section lengths against
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the file, biome/tier ordinal ranges.
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- **v1 (legacy)** — the positional `"ISLA_V1"` format, still written beside v2 as `_v1.dat` and
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still loadable (with a deprecation warning) until a future removal task.
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⚠ **Wire-format hazard.** Biome and town-tier enums are serialized as their **ordinal values**
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(u8 in v2, i32 in v1). **Never reorder or insert members** in `Enums.cs` — append only, at the end.
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v2's range checks make drift fail loudly at parse time; legacy v1 has no validation and silently
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reinterprets every pixel. (`RoadTier` is exempt: road tiers are stored in separate file sections —
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tagged in v2, positional in v1 — so that enum never hits disk.)
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### `ChunkData.cs` + `Constants.cs` — voxel containers and tuning
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- **Chunk dimensions:** `24 × 24` horizontal, `256` vertical (`Constants.cs`).
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- **The `+1` padding is structural.** `Densities` and `BlockIDs` are one cell larger on every axis —
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`[25, 257, 25]` — so the mesher can evaluate the boundary cells shared with the neighbouring chunk
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and the meshes meet without gaps.
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- **Per-column data for rendering:** `SurfaceHeights` (the true, unrounded surface), `ColumnBiomes`,
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and `ColumnRoadMaterial` (0 = not a road). These let the mesher colour by real height rather than a
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rounded integer.
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- **Tunables in `Constants.cs`:** `BLEND_BAND_METERS` (how far one surface material fades into the
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next) and the per-tier road block — width, shoulder, grade-smoothing and surface material for each
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of the four road tiers, plus the derived cull padding.
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### `MarchingCubes.cs` — the mesher
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Turns a chunk's density field into a Godot `ArrayMesh`.
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- **Analytical normals:** exact density gradients at each cell corner, interpolated along the edge by
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the same fraction used for the vertex position — smooth lighting without Godot's normal pass.
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- **Deterministic vertex welding:** shared vertices are keyed by an integer `EdgeKey` ordered
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lowest-to-highest, so neighbouring chunks compute identical keys and no float drift creeps in.
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- **Vertex colouring:** each vertex is coloured from its true float depth below the surface, fading
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between the two materials either side of a boundary rather than switching at an integer depth.
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**Density sign convention (load-bearing):** density is **positive above** the surface and **negative
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below** it. A corner counts as inside the terrain when `density < ISO_LEVEL`.
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### `BiomePalette.cs` + `BlockRegistry.cs` + `BlockData.cs` — materials
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- **`BlockRegistry`:** byte-ID lookup for every block (`AIR`, `BEDROCK`, `STONE`, `DIRT`, `SAND`, the
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three grasses, `SNOW`, `WASTELAND_DIRT`, `ASPHALT`).
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- **`BiomePalette`** answers "what material is here?" twice, deliberately:
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- `GetVoxelID(...)` — the authoritative **integer** classification by whole-block depth. Decides
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what is actually stored in each voxel; used for everything non-visual.
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- `GetBlendedVoxelIDs(...)` — the **rendering** version. Same question by *float* depth, returning
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the two materials either side of the nearest boundary plus how far between them the point is, so
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the renderer fades instead of snapping.
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Both take a road-surface byte, so a trail is surfaced in dirt where a highway is surfaced in
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asphalt.
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