package d2mapengine import ( "github.com/OpenDiablo2/OpenDiablo2/d2common/d2enum" "github.com/OpenDiablo2/OpenDiablo2/d2common/d2fileformats/d2ds1" "github.com/OpenDiablo2/OpenDiablo2/d2common/d2fileformats/d2dt1" ) // MapTile is a tile placed on the map type MapTile struct { Components d2ds1.TileRecord RegionType d2enum.RegionIdType SubTiles [25]d2dt1.SubTileFlags } // GetSubTileFlags returns the tile flags for the given subtile func (t *MapTile) GetSubTileFlags(x, y int) *d2dt1.SubTileFlags { var subtileLookup = [5][5]int{ {20, 21, 22, 23, 24}, {15, 16, 17, 18, 19}, {10, 11, 12, 13, 14}, {5, 6, 7, 8, 9}, {0, 1, 2, 3, 4}, } return &t.SubTiles[subtileLookup[y][x]] } // PrepareTile selects which graphic to use and updates the tiles subtileflags func (t *MapTile) PrepareTile(x, y int, me *MapEngine) { for wIdx := range t.Components.Walls { wall := &t.Components.Walls[wIdx] options := me.GetTiles(int(wall.Style), int(wall.Sequence), wall.Type) if options == nil { break } wall.RandomIndex = getRandomTile(options, x, y, me.seed) for i := range t.SubTiles { t.SubTiles[i].Combine(options[wall.RandomIndex].SubTileFlags[i]) } } for fIdx := range t.Components.Floors { floor := &t.Components.Floors[fIdx] options := me.GetTiles(int(floor.Style), int(floor.Sequence), 0) if options == nil { break } if options[0].MaterialFlags.Lava { floor.Animated = true floor.RandomIndex = 0 } else { floor.RandomIndex = getRandomTile(options, x, y, me.seed) } for i := range t.SubTiles { t.SubTiles[i].Combine(options[floor.RandomIndex].SubTileFlags[i]) } } for sIdx := range t.Components.Shadows { shadow := &t.Components.Shadows[sIdx] options := me.GetTiles(int(shadow.Style), int(shadow.Sequence), 13) if options == nil { break } shadow.RandomIndex = getRandomTile(options, x, y, me.seed) for i := range t.SubTiles { t.SubTiles[i].Combine(options[shadow.RandomIndex].SubTileFlags[i]) } } } // Walker's Alias Method for weighted random selection with xorshifting for random numbers // Selects a random tile from the slice, rest of args just used for seeding func getRandomTile(tiles []d2dt1.Tile, x, y int, seed int64) byte { var tileSeed uint64 tileSeed = uint64(seed) + uint64(x) tileSeed *= uint64(y) const ( xorshiftA = 13 xorshiftB = 17 xorshiftC = 5 ) tileSeed ^= tileSeed << xorshiftA tileSeed ^= tileSeed >> xorshiftB tileSeed ^= tileSeed << xorshiftC weightSum := 0 for i := range tiles { weightSum += int(tiles[i].RarityFrameIndex) } if weightSum == 0 { return 0 } random := tileSeed % uint64(weightSum) sum := 0 for i := range tiles { sum += int(tiles[i].RarityFrameIndex) if sum >= int(random) { return byte(i) } } // This return shouldn't be hit return 0 }