78 lines
3.0 KiB
Markdown
78 lines
3.0 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 `server/src/map.rs`; wired into the world in `server/src/main.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` on
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the client plus the flags carried through the protocol; 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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- **Server** — `tile_flags(id)` (in `map.rs`) maps an id to gameplay `TileFlags`
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(collidable / opaque). Hand-maintained vocabulary; currently everything is walkable floor.
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- **Client** — the id indexes straight into `overworld.tga` (`game.rs`). The tileset's tile
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order *is* the id space; keep the Tiled tileset and `overworld.tga` in lockstep.
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No `firstgid` subtraction: the authored ids already line up with `overworld.tga`.
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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`, which builds each chunk's
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6-bit palette automatically. The map's top-left tile sits at world (0, 0).
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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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