handmadehero/handmade_tile.cpp

#include "handmade_tile.h"

static tile_chunk *GetTileChunk(tile_map *TileMap,
                                U32 TileChunkX,
                                U32 TileChunkY,
                                U32 TileChunkZ)
{
    tile_chunk *TileChunk = NULL;

    if((TileChunkX >= 0) && (TileChunkX < TileMap->TileChunkCountX) &&
       (TileChunkY >= 0) && (TileChunkY < TileMap->TileChunkCountY) &&
       (TileChunkZ >= 0) && (TileChunkZ < TileMap->TileChunkCountZ))
    {
        TileChunk =
            &TileMap->TileChunks[
            (TileChunkZ*TileMap->TileChunkCountY*TileMap->TileChunkCountX) +
            (TileChunkY*TileMap->TileChunkCountX) +
            TileChunkX];
    }

    return TileChunk;
}

static void CannonicalizeCoord(tile_map *TileMap, U32 *Tile, F32 *TileRel)
{
    /* NOTE: The world is assumed to be toroidal topology. If you step off
             one end, you come back on the other. */
    S32 Offset = RoundF32toS32(*TileRel / TileMap->TileSideInMeters);
    *Tile += Offset;
    *TileRel -= (F32)Offset * TileMap->TileSideInMeters;

    ASSERT(*TileRel >= -0.5f*TileMap->TileSideInMeters);
    ASSERT(*TileRel <= 0.5f*TileMap->TileSideInMeters);
}

static tile_map_position RecannonicalizePosition(tile_map *TileMap,
                                                 tile_map_position Pos)
{
    tile_map_position Result = Pos;

    CannonicalizeCoord(TileMap, &Result.AbsTileX, &Result.TileRelX);
    CannonicalizeCoord(TileMap, &Result.AbsTileY, &Result.TileRelY);

    return Result;
}

static tile_chunk_position GetChunkPositionFor(tile_map *TileMap,
                                               U32 AbsTileX,
                                               U32 AbsTileY,
                                               U32 AbsTileZ)
{
    tile_chunk_position Result;

    Result.TileChunkX = AbsTileX >> TileMap->ChunkShift;
    Result.TileChunkY = AbsTileY >> TileMap->ChunkShift;
    Result.TileChunkZ = AbsTileZ;
    Result.RelTileX   = AbsTileX & TileMap->ChunkMask;
    Result.RelTileY   = AbsTileY & TileMap->ChunkMask;

    return Result;
}

static U32 GetTileValueUnchecked(tile_map *TileMap, tile_chunk *TileChunk,
                                  U32 TileX, U32 TileY)
{
    U32 TileChunkValue;

    ASSERT(TileChunk);
    ASSERT(TileX < TileMap->ChunkDim);
    ASSERT(TileY < TileMap->ChunkDim);

    TileChunkValue = TileChunk->Tiles[TileY * TileMap->ChunkDim + TileX];
    return TileChunkValue;
}

static void SetTileValueUnchecked(tile_map *TileMap, tile_chunk *TileChunk,
                                 U32 TileX, U32 TileY, U32 TileValue)
{
    ASSERT(TileChunk);
    ASSERT(TileX < TileMap->ChunkDim);
    ASSERT(TileY < TileMap->ChunkDim);

    TileChunk->Tiles[TileY * TileMap->ChunkDim + TileX] = TileValue;
}

static U32 GetTileChunkValue(tile_map *TileMap, tile_chunk *TileChunk,
                             U32 TestTileX, U32 TestTileY)
{
    U32 TileChunkValue = 0;

    if(TileChunk && TileChunk->Tiles) {
        TileChunkValue = GetTileValueUnchecked(TileMap,
                                               TileChunk,
                                               TestTileX,
                                               TestTileY);
    }

    return TileChunkValue;
}

static void SetTileChunkValue(tile_map *TileMap, tile_chunk *TileChunk,
                             U32 TestTileX, U32 TestTileY,
                             U32 TileValue)
{
    if(TileChunk && TileChunk->Tiles) {
        SetTileValueUnchecked(TileMap,
                              TileChunk,
                              TestTileX, TestTileY,
                              TileValue);
    }
}

static U32 GetTileValue(tile_map *TileMap,
                        U32 AbsTileX, U32 AbsTileY, U32 AbsTileZ)
{
    tile_chunk_position ChunkPos = GetChunkPositionFor(TileMap,
                                                       AbsTileX,
                                                       AbsTileY,
                                                       AbsTileZ);
    tile_chunk *TileChunk = GetTileChunk(TileMap,
                                         ChunkPos.TileChunkX,
                                         ChunkPos.TileChunkY,
                                         ChunkPos.TileChunkZ);
    U32 TileChunkValue = GetTileChunkValue(TileMap, TileChunk,
                                           ChunkPos.RelTileX,
                                           ChunkPos.RelTileY);
    return TileChunkValue;
}

static B32 IsTileMapPointEmpty(tile_map *TileMap, tile_map_position CanPos)
{
    B32 Empty;

    U32 TileChunkValue = GetTileValue(TileMap,
                                      CanPos.AbsTileX,
                                      CanPos.AbsTileY,
                                      CanPos.AbsTileZ);
    Empty = (TileChunkValue == 1);
    return Empty;
}

static void SetTileValue(memory_arena *Arena,
                         tile_map *TileMap,
                         U32 AbsTileX, U32 AbsTileY, U32 AbsTileZ,
                         U32 TileValue)
{
    tile_chunk_position ChunkPos;
    tile_chunk *TileChunk;

    ChunkPos = GetChunkPositionFor(TileMap, AbsTileX, AbsTileY, AbsTileZ);
    TileChunk = GetTileChunk(TileMap,
                             ChunkPos.TileChunkX,
                             ChunkPos.TileChunkY,
                             ChunkPos.TileChunkZ);

    ASSERT(TileChunk);
    if(!TileChunk->Tiles) {
        U32 TileCount = TileMap->ChunkDim*TileMap->ChunkDim;
        U32 TileIndex;

        TileChunk->Tiles = PUSH_ARRAY(Arena, TileCount, U32);
        for(TileIndex = 0; TileIndex < TileCount; TileIndex++) {
            TileChunk->Tiles[TileIndex] = 1;
        }

    }

    SetTileChunkValue(TileMap, TileChunk,
                     ChunkPos.RelTileX,
                     ChunkPos.RelTileY,
                     TileValue);
}