voxel_engine

The engine under a voxel game, in pure Dart: a chunk grid, meshing with light and ambient occlusion, streaming on worker isolates, physics, rays, world generation, blocks and items, circuits and a network layer. It draws nothing — a renderer (voxel_scene) takes the meshes, and voxel_game ties everything into a playable game.

Status: 0.4.0-dev, beta. The API can still change.

The five subjects

Each one is a library of its own. Import only what you use, or package:voxel_engine/voxel_engine.dart for all of it.

Library	What it does	Depends on
core.dart	chunk grid, mesher, streaming, physics, rays, liquids, pathfinding, the edit save format	—
worldgen.dart	biomes, terrain, caves, ores, trees, structures, as a declared spec	core
content.dart	blocks and items by string id, mining, inventory, crafting, loot, effects	core
signals.dart	wires, levers, lamps, doors, pistons, and rails that lay themselves	core
net.dart	a TCP host and its clients, exchanging JSON messages	—

Install

dependencies:
  voxel_engine: ^0.4.0-dev

Dart SDK ^3.13.0. No Flutter dependency: it runs in dart test, on a server and on worker isolates. Not on the web: streaming spawns isolates and net.dart is TCP sockets, through dart:isolate and dart:io, which a browser does not have.

Usage

core — a world you can walk in

1. Describe your blocks. Id 0 is air.

   final table = VoxelBlockTable(const [
     VoxelBlockDef(shape: BlockShape.cube, solid: false, opaque: false, r: 0, g: 0, b: 0, a: 0), // air
     VoxelBlockDef(shape: BlockShape.cube, solid: true, opaque: true, r: 0.4, g: 0.4, b: 0.45),  // stone
   ]);
   

2. Write a generator. It fills one chunk and must be pure in the position.

   class Flat implements ChunkGenerator {
     const Flat();
     @override
     Uint8List generateIn(int cx, int cz, int dimension) {
       final blocks = Uint8List(ChunkSize.volume);
       for (var z = 0; z < ChunkSize.sizeZ; z++) {
         for (var x = 0; x < ChunkSize.sizeX; x++) {
           for (var y = 0; y < 40; y++) {
             blocks[ChunkSize.index(x, y, z)] = 1;
           }
         }
       }
       return blocks;
     }
   }
   
   ChunkGenerator makeGenerator() => const Flat(); // top-level: sent to each isolate
   

3. Stream chunks around a point. The sink receives each finished mesh.

   final pool = ChunkWorkerPool(ChunkWorkerConfig(generator: makeGenerator, table: table));
   await pool.start();
   final streamer = ChunkStreamer(table: table, sink: mySink, loadRadius: 4)
     ..jobs = pool
     ..updateAround((x: 0, z: 0));
   // Once a frame:
   streamer.update();
   

4. Read and edit the world. streamer.getBlockXYZ, streamer.setBlock, VoxelRaycast.solid(...) for aiming, VoxelBody for anything that walks.

5. Save only the edits with EditDeltaCodec; the generator rebuilds the rest.

content — blocks, items and what the player carries

1. Declare blocks. Air first; the order numbers them for the engine, and blocks.table is the VoxelBlockTable step 1 above asked for. A row also says what the block does, for a game to act on: it falls, it needs a support (Support.below, Support.side; blocks.stands answers whether it would stay), it has an onWall form, it drops a rolled loot, it turns to face the placer (Facing.compass, Facing.axis), it is two cells tall, a use turns it into another (usedInto), it grows into its next stage (a Growth), a tool turns it into another (turnsWith), it stores things (a Storage of slots, and the loot a generated one holds).

   final blocks = BlockRegistry(const [
     BlockType('air', color: 0, solid: false, hardness: -1, drop: ''),
     BlockType('stone', color: 0x7F7F84, hardness: 1.5, tool: 'pickaxe', tier: 1, drop: 'cobblestone'),
     BlockType('cobblestone', color: 0x6E6E70, hardness: 2.0, tool: 'pickaxe'),
   ]);
   

2. Declare items. Every block you can hold is an item already (a block only the world makes says holdable: false). One that is eaten says what it does in food (a Food that cures ends the bad effects), one that is worn where in armor, one that carries a liquid in bucket (Bucket.empty, Bucket.full), one that shoots in launcher (Launcher(shot:, ammo:)), one that lights the way in hand in light, one that glides in glider. What it looks like is its shape, or one read off the rest of its row; ItemModel.of(item, blocks, items) builds its voxels.

   final items = ItemRegistry([
     ...ItemRegistry.forBlocks(blocks),
     const ItemType('wooden_pickaxe', color: 0xB08850, tool: 'pickaxe', tier: 1, stack: 1, durability: 60),
     const ItemType('apple', color: 0xD03A2A, food: Food(hunger: 4)),
     const ItemType('wool_tunic', color: 0xE8E8E8, stack: 1, armor: Armor('chest', 3)),
     const ItemType('wool_cap', color: 0xE8E8E8, stack: 1, armor: Armor('head', 1), shape: ItemShape.cap),
   ]);
   

3. Mine. const MiningRules().mineTime(block, tool) gives seconds, or -1 when that tool cannot break it; a tool whose kind cuts a block's tag takes it at once (shears through leaves).

4. Carry things.

   final bag = Inventory(stackSize: (id) => items[id].stack, maxDurability: (id) => items[id].durability)
     ..add('cobblestone', 10);
   

5. Craft.

   final book = RecipeBook(const [Recipe('stone', 1, {'cobblestone': 1}, station: 'furnace')]);
   book.craft(book.available('furnace').first, bag);
   

6. Roll loot. A LootTable rolls each entry by its own chance (a chest, a mob's drops); a LootTable.oneOf gives one entry or nothing, each chance a slice of one roll (a fishing line's catch). check() throws for slices summing over 1.

   const catches = LootTable.oneOf([LootEntry('raw_fish', 1, 1, 0.7), LootEntry('stick', 1, 2, 0.15)]);
   final got = catches.roll(math.Random()); // raw_fish 70 %, sticks 15 %, nothing 15 %
   

worldgen — a world declared instead of coded

1. Give it your block ids. A BlockRegistry already has them: blocks.ids.

2. Declare the world.

   const world = WorldGenSpec(
     biomes: [
       Biome('forest', top: 'grass', under: 'dirt', climate: Climate.wet,
           trees: [TreeSpec.oak(log: 'log', leaves: 'leaves')], treeChance: 90),
       Biome('plains', top: 'grass', under: 'dirt'),
     ],
     beach: Biome('beach', top: 'sand'),
     ores: [Ore('coal_ore', share: 0.11)],
   );
   

3. Compile it with a seed and use it as the ChunkGenerator of step 2 above.

   ChunkGenerator makeGenerator() => world.compile(blocks.ids, 2024);
   

4. Ask it about the world without generating chunks: surfaceHeight(x, z), biomeAt(x, z), structuresNear(cx, cz).

5. Add structures: a stock one (Dungeon, Tower, Well, Camp, Ruins, Mine, Village, Temple) takes its blocks by name; your own is a build function. Structures keep apart: a site within reach of an earlier one's is dropped. A dungeon's and a mine's parts are where their plan says, so a game finds them without reading the world: DungeonPlan.of(dungeon, site, generator.rollOf(site)).spawners, MinePlan.of(...).chest.

   void tower(StructureSite s) {
     s.level(-2, -2, 2, 2, 'stone', clearTo: 10);
     s.fill(-2, 0, -2, 2, 8, 2, 'stone', hollow: true);
   }
   // structures: [
   //   StructureSpec('well', Well(rim: 'cobblestone', water: 'water', posts: 'fence', roof: 'planks')),
   //   StructureSpec('tower', CustomStructure(tower, radius: 3, blocks: {'stone'}), biomes: ['plains']),
   // ]
   

6. Dress the ground with rows: strata (dark stone in the deep), a biome's covers (snow above a height, patches of mud), pools (water over mud), trees by weight, and plants that grow taller (maxHeight), in patches (spread) or by water (byWater), low ground pressed toward the sea (flats, a swamp), and biomes of their own on the beach's columns (shores, a frozen one).

7. Other kinds of world. A cavern (CavernSpec) is one great cave between a bedrock floor and roof; a plaza (Plaza, or withPlaza) is a square of open ground pressed flat, a showroom's floor; a DimensionGenerator hands each dimension's chunks to its own spec, for the worker isolates.

signals — circuits and rails

1. Tell the network about every edit. It needs a VoxelEditor, and your world calls touch whenever a block changes:

   @override
   bool setBlock(IVec3 cell, int id) {
     final old = getBlockXYZ(cell.x, cell.y, cell.z);
     // ...write the block...
     signals.touch(cell, old, id);
     return true;
   }
   

2. Declare the circuit blocks.

   final signals = SignalNetwork(world, SignalRules(
     wireOff: wireOff,
     wireOn: wireOn,
     sources: const {leverOn},
     toggles: const {leverOff: leverOn, leverOn: leverOff},
     reactions: {
       lampOff: SignalReactions.swap(lampOff, lampOn),
       lampOn: SignalReactions.swap(lampOff, lampOn),
     },
   ));
   

3. Tick it every frame with signals.tick(dt), and call signals.use(cell) when the player clicks a lever.

4. Rails: name each rail shape once, then place rails through the graph.

   final rails = RailGraph({railNs: const RailVariant('rail', 'ns'), railEw: const RailVariant('rail', 'ew') /* ... */});
   rails.place(world, cell, railNs); // turns to meet its neighbours
   final next = rails.nextCell(world, cell, RailGraph.e);
   

net — two games in one world

1. Host.

   final host = await NetHost.bind(port: 7777);
   host
     ..onJoin = ((peer) => print('player ${peer.id} joined'))
     ..onMessage = ((peer, message) => host.broadcast(message, except: peer.id))
     ..onLeave = ((peer) => print('player ${peer.id} left'));
   

2. Join from another app or machine.

   final client = await connectToHost('192.168.0.10', port: 7777);
   

3. Talk. Messages are JSON objects; t says what they are.

   client.send({'t': 'pose', 'p': [12.5, 64.0, -3.0]});
   client.listen((message) => print(message['t']));
   

4. Leave. await client.close(); runs the host's onLeave, and await host.close(); drops everyone.

   On macOS, a Flutter app that hosts or joins needs the com.apple.security.network.server and com.apple.security.network.client entitlements.

Examples

Six files, each runnable on its own:

dart run example/voxel_engine_example.dart   # the subjects in one run
dart run example/core_example.dart           # streaming, rays, edits, a falling body
dart run example/worldgen_example.dart       # a text map of a four-biome world, then 25 chunks
dart run example/content_example.dart        # blocks, mining, a bag, crafting, loot, effects
dart run example/signals_example.dart        # a lever lights a lamp; a cart rides a rail line
dart run example/net_example.dart            # a host and a client over localhost

example/voxel_engine_example.dart is the one to read first: content declares the blocks, worldgen builds a world out of the same ids, core meshes a chunk and casts a ray into it, and content mines what the ray hit into a bag.