irrlichtandClaude Opus 5
1d14076468
The 64-entry per-chunk palette was a wire-format artifact and capped a chunk at 64 distinct tiles. A Chunk is now Box<[u16; 1024]> with flags derived from the id on lookup — the same layout a binary on-disk format would use. Map path becomes the first CLI argument; assets/map_large is a generated 256×256 stress map (loads in ~0.5 ms release). The snapshot test takes SNAPSHOT_MAP. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
82 lines
3.4 KiB
Markdown
82 lines
3.4 KiB
Markdown
# Map Loader
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Loads level data from a Tiled CSV export, replacing the old hardcoded `build_world` wall loop.
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Implemented in `sim/src/map.rs`; wired into the world in `sim/src/lib.rs::load_world`.
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---
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## Format
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A bare comma-separated tile grid — Tiled's "CSV" layer export, stripped of the surrounding
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TMX/XML. No header, no dimensions. The loader derives them from the content:
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- **width** = number of fields in the first row
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- **height** = number of rows
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The current test map lives at `assets/map_test` (30×30, tile ids 25 / 74 / 75 / 146).
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A trailing comma per row is tolerated; ragged rows panic (they indicate a corrupt export).
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---
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## Tile flip flags — the "negative numbers"
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Tiled packs per-tile flip/rotation into the **top 3 bits** of each 32-bit GID. A flipped tile
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therefore shows up in the CSV as a large *negative* decimal when read as `i32`. Example:
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```
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-2147483574 as u32 = 0x8000004A
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│ └── 0x4A = 74 ← the real tile id
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└────────── 0x80000000 = horizontal flip
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```
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| Bit | Mask | Meaning |
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|-----|--------------|---------------------|
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| 31 | `0x80000000` | horizontal flip |
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| 30 | `0x40000000` | vertical flip |
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| 29 | `0x20000000` | diagonal flip (rot) |
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The loader parses each field as `i64`, reinterprets the low 32 bits as `u32`, and strips the
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flip flags with `& 0x1FFF_FFFF`, leaving the bare tile id. **Flip orientation is discarded for
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now** — flipped tiles render unflipped. Real flipping would need a flip-aware `blit_tile` plus
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a flip flag next to the tile id in the chunk; deferred to the camera/sprite pass (09).
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---
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## Tile id ↔ tileset
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Tile ids are used directly:
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- **Sim** — `tile_flags(id)` (in `map.rs`) maps an id to gameplay `TileFlags`
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(collidable / opaque) via the `sim::tile_collidable` vocabulary. Hand-maintained; test values only.
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- **Renderer** — the id indexes straight into `overworld.png` (`game.rs`). The tileset's tile
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order *is* the id space; keep the Tiled tileset and `overworld.png` in lockstep.
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No `firstgid` subtraction: the authored ids already line up with `overworld.png`.
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---
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## World assembly
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`load_world` slices the map into 32×32 chunks via `Chunk::generate`. A chunk is a plain
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`[u16; 1024]` of tile ids; flags are derived from the id on lookup (`map::tile_flags`). That
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array is also the natural on-disk layout should chunks ever be streamed from disk (RLE over
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the `u16`s would do) — the CSV stays the interchange format for external tooling. The map's
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top-left tile sits at world (0, 0). Loading a 256×256 map takes well under a millisecond in
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release; the map path is the game's first CLI argument (`game assets/map_large`).
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**Edge border:** a 30×30 map only fills part of chunk (0,0) (which spans tiles 0–31). Tiles
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inside a loaded chunk but outside the authored map are emitted as an *invisible solid border*
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(id 0, `COLLIDABLE`) so the walkable edge sits flush with the visible map rim rather than two
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tiles past it at the chunk boundary. Beyond any loaded chunk, movement is blocked anyway by
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`sim.rs`'s `map_or(true)` (no chunk = world edge).
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---
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## Not done yet
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- Multiple layers (only a single tile layer is read)
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- Tile properties from Tiled (collision comes from the hand-maintained `tile_flags`, not the file)
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- Object layers (spawns, triggers)
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- Tile flipping (orientation discarded — see above)
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</content>
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