Docs

2026-06-18 14:59:21 -05:00
parent 6135d60ddc
commit 730a5b2b10
17 changed files with 2825 additions and 415 deletions
@@ -0,0 +1,114 @@
+# World
+
+Source: `src/dusk/rpg/overworld/`
+
+---
+
+## Coordinate system
+
+Three nested coordinate spaces, each defined in `worldpos.h`:
+
+| Type | Description | Unit |
+|---|---|---|
+| `worldpos_t` | Tile-level absolute position `{x, y, z}` | `worldunit_t` (int16) |
+| `chunkpos_t` | Chunk-grid position `{x, y, z}` | `chunkunit_t` (int16) |
+| `fixed_t[3]` | Smooth sub-tile position used by entities | Q24.8 fixed-point |
+
+One chunk = `CHUNK_WIDTH × CHUNK_HEIGHT × CHUNK_DEPTH` tiles (16 × 16 × 8).
+The loaded world window = `MAP_CHUNK_WIDTH × MAP_CHUNK_HEIGHT × MAP_CHUNK_DEPTH` chunks (5 × 5 × 3).
+
+Conversion helpers (all in `worldpos.c`):
+
+```c
+worldPosToChunkPos(&worldPos, &chunkPos);   // tile → chunk grid
+chunkPosToWorldPos(&chunkPos, &worldPos);   // chunk grid → tile origin
+worldPosToChunkTileIndex(&worldPos);        // tile → index within its chunk
+chunkPosToIndex(&chunkPos);                 // chunk grid → linear index in MAP.chunks[]
+worldPosToFixed(&worldPos, fixedOut);       // tile → entity fixed position
+fixedToWorldPos(fixedPos);                  // entity fixed → tile (truncates frac)
+```
+
+---
+
+## Tiles
+
+Defined in `tile.h` as a plain `tile_t` enum:
+
+```
+TILE_SHAPE_NULL    — empty / unloaded
+TILE_SHAPE_GROUND  — solid flat tile
+TILE_SHAPE_RAMP_*  — directional ramps (N/S/E/W + diagonals NE/NW/SE/SW)
+```
+
+Key predicates:
+- `tileIsWalkable(tile)` — true for GROUND and all ramp shapes.
+- `tileIsRamp(tile)` — true only for ramp shapes.
+
+Entity walk code (`entity.c`) checks both the current tile and the target tile to decide whether the entity steps forward flat, raises one Z level (walking up a ramp), or falls one Z level (stepping onto a downward ramp from above).
+
+---
+
+## Chunks
+
+`chunk_t` (`chunk.h`) holds:
+- `position` — its `chunkpos_t` in the world grid
+- `tiles[CHUNK_TILE_COUNT]` — flat array of `tile_t`, indexed by `chunkGetTileIndex()`
+- `vertices[CHUNK_VERTEX_COUNT]` / `mesh` — pre-baked mesh uploaded to GPU on load
+- `entities[CHUNK_ENTITY_COUNT_MAX]` — indices into `ENTITIES[]` currently in this chunk (sentinel `0xFF`)
+- `testColor` — temporary debug color (checkerboard), will be replaced by real tileset data
+
+Tile layout within a chunk is `z * W*H + y * W + x` (Z-major, row-major in XY).
+
+---
+
+## Map
+
+`map_t MAP` (`map.h`) is the single global map instance.
+
+```c
+chunk_t chunks[MAP_CHUNK_COUNT];         // flat storage — index is NOT world position
+chunk_t *chunkOrder[MAP_CHUNK_COUNT];    // draw-order sorted pointers into chunks[]
+chunkpos_t chunkPosition;               // world-grid origin of the loaded window
+bool_t loaded;
+```
+
+### Load / unload
+
+`mapInit()` allocates chunk meshes and performs the initial load of all chunks in the starting window.
+
+`mapPositionSet(newPos)` shifts the window:
+1. Determines which of the `MAP_CHUNK_COUNT` slots remain within the new window vs. fall outside it.
+2. Calls `mapChunkUnload()` on every chunk that falls outside (nulls its entity slots, zeroes `vertCount`).
+3. Reuses freed slots for newly-in-range chunks; calls `mapChunkLoad()` on each.
+4. Rebuilds `chunkOrder[]` in XYZ order for the new position.
+
+### Chunk load (current stub)
+
+`mapChunkLoad()` currently:
+- Fills all tiles with `TILE_SHAPE_GROUND`
+- Assigns a checkerboard debug color based on chunk XY parity
+- Bakes a flat sprite-batch quad mesh for the z=0 layer and uploads it via `meshFlush()`
+- Skips mesh generation for z > 0 chunks (they're empty)
+
+### Tile lookup
+
+```c
+tile_t mapGetTile(const worldpos_t position);
+```
+
+Converts `position` to its chunk, looks up the chunk in `chunkOrder`, then indexes into `chunk->tiles[]`. Returns `TILE_SHAPE_NULL` for any out-of-bounds position or when the map is not loaded.
+
+---
+
+## Camera
+
+`rpgcamera_t RPG_CAMERA` (`rpgcamera.h`) has two modes:
+
+```c
+RPG_CAMERA_MODE_FREE            // free worldpos; camera.free holds the position
+RPG_CAMERA_MODE_FOLLOW_ENTITY   // tracks ENTITIES[followEntityId]
+```
+
+`rpgCameraGetPosition()` returns the active world tile position in either mode.
+
+The scene renderer (`sceneoverworld.c`) uses `rpgCameraGetPosition()` to build the `glm_lookat` view matrix. When following an entity, it sub-tile interpolates between `entity->lastPosition` and `entity->position` using `entity->animTime / ENTITY_ANIM_WALK_DURATION` to smooth movement.