Get entity movement working

examples/chunk.rs

@@ -109,12 +109,6 @@ impl Config for Game {
                 }
             }
         }
-
-        let entity_id = world.entities.create();
-        let mut entity = world.entities.get_mut(entity_id).unwrap();
-
-        entity.set_type(EntityType::Cow);
-        entity.set_position([0.0, 50.0, 0.0]);
     }
 
     fn update(&self, server: &Server, mut worlds: WorldsMut) {

examples/cow_sphere.rs

@@ -0,0 +1,119 @@
+use std::net::SocketAddr;
+use std::sync::atomic::{AtomicUsize, Ordering};
+
+use log::LevelFilter;
+use valence::block::BlockState;
+use valence::client::GameMode;
+use valence::config::{Config, ServerListPing};
+use valence::text::Color;
+use valence::{
+    async_trait, ChunkPos, ClientMut, DimensionId, EntityType, Server, ShutdownResult, Text,
+    TextFormat, WorldId, WorldsMut,
+};
+
+pub fn main() -> ShutdownResult {
+    env_logger::Builder::new()
+        .filter_module("valence", LevelFilter::Trace)
+        .parse_default_env()
+        .init();
+
+    valence::start_server(Game {
+        player_count: AtomicUsize::new(0),
+    })
+}
+
+struct Game {
+    player_count: AtomicUsize,
+}
+
+const MAX_PLAYERS: usize = 10;
+
+#[async_trait]
+impl Config for Game {
+    fn max_connections(&self) -> usize {
+        // We want status pings to be successful even if the server is full.
+        MAX_PLAYERS + 64
+    }
+
+    fn online_mode(&self) -> bool {
+        // You'll want this to be true on real servers.
+        false
+    }
+
+    async fn server_list_ping(&self, _server: &Server, _remote_addr: SocketAddr) -> ServerListPing {
+        ServerListPing::Respond {
+            online_players: self.player_count.load(Ordering::SeqCst) as i32,
+            max_players: MAX_PLAYERS as i32,
+            description: "Hello Valence!".color(Color::AQUA),
+            favicon_png: Some(include_bytes!("favicon.png")),
+        }
+    }
+
+    fn join(
+        &self,
+        _server: &Server,
+        _client: ClientMut,
+        worlds: WorldsMut,
+    ) -> Result<WorldId, Text> {
+        if let Ok(_) = self
+            .player_count
+            .fetch_update(Ordering::SeqCst, Ordering::SeqCst, |count| {
+                (count < MAX_PLAYERS).then(|| count + 1)
+            })
+        {
+            Ok(worlds.iter().next().unwrap().0)
+        } else {
+            Err("The server is full!".into())
+        }
+    }
+
+    fn init(&self, _server: &Server, mut worlds: WorldsMut) {
+        let world_id = worlds.create(DimensionId::default());
+        let mut world = worlds.get_mut(world_id).unwrap();
+        world.meta.set_flat(true);
+
+        let size = 5;
+        for z in -size..size {
+            for x in -size..size {
+                world.chunks.create([x, z]);
+            }
+        }
+
+        let entity_id = world.entities.create();
+        let mut entity = world.entities.get_mut(entity_id).unwrap();
+
+        entity.set_type(EntityType::Cow);
+        entity.set_position([0.0, 100.0, 0.0]);
+        //entity.set_yaw(30.0);
+        //entity.set_pitch(0.0);
+    }
+
+    fn update(&self, server: &Server, mut worlds: WorldsMut) {
+        let mut world = worlds.iter_mut().next().unwrap().1;
+
+        world.clients.retain(|_, mut client| {
+            if client.created_tick() == server.current_tick() {
+                client.set_game_mode(GameMode::Creative);
+                client.teleport([0.0, 200.0, 0.0], 0.0, 0.0);
+            }
+
+            if client.is_disconnected() {
+                self.player_count.fetch_sub(1, Ordering::SeqCst);
+                false
+            } else {
+                true
+            }
+        });
+
+        for (_, mut e) in world.entities.iter_mut() {
+            let time = server.current_tick() as f64 / server.tick_rate() as f64;
+
+            if e.typ() == EntityType::Cow {
+                e.set_position(e.position() + [0.0, 0.0, 0.02]);
+                let yaw = (time % 1.0 * 360.0) as f32;
+                e.set_yaw(yaw);
+                e.set_head_yaw(yaw);
+            }
+        }
+    }
+}

src/chunk.rs

@@ -418,7 +418,8 @@ fn encode_paletted_container(
                     let palette_idx = palette
                         .iter()
                         .position(|&e| e == entry)
-                        .expect("entry should be in the palette") as u64;
+                        .expect("entry should be in the palette")
+                        as u64;
 
                     val |= palette_idx << (i * bits_per_idx);
                 }

src/client.rs

@@ -8,25 +8,29 @@ use uuid::Uuid;
 use vek::Vec3;
 
 use crate::block_pos::BlockPos;
+use crate::byte_angle::ByteAngle;
 use crate::config::{
     Biome, BiomeGrassColorModifier, BiomePrecipitation, Dimension, DimensionEffects, DimensionId,
 };
-use crate::entity::EntityType;
+use crate::entity::{velocity_to_packet_units, EntityType};
 pub use crate::packets::play::GameMode;
 use crate::packets::play::{
     Biome as BiomeRegistryBiome, BiomeAdditionsSound, BiomeEffects, BiomeMoodSound, BiomeMusic,
     BiomeParticle, BiomeParticleOptions, BiomeProperty, BiomeRegistry, ChangeGameState,
     ChangeGameStateReason, ClientPlayPacket, DestroyEntities, DimensionCodec, DimensionType,
-    DimensionTypeRegistry, DimensionTypeRegistryEntry, Disconnect, JoinGame, KeepAliveClientbound,
+    DimensionTypeRegistry, DimensionTypeRegistryEntry, Disconnect, EntityHeadLook, EntityPosition,
-    PlayerPositionAndLook, PlayerPositionAndLookFlags, ServerPlayPacket, SpawnPosition,
+    EntityPositionAndRotation, EntityRotation, EntityTeleport, EntityVelocity, JoinGame,
-    UnloadChunk, UpdateViewDistance, UpdateViewPosition,
+    KeepAliveClientbound, PlayerPositionAndLook, PlayerPositionAndLookFlags, ServerPlayPacket,
+    SpawnPosition, UnloadChunk, UpdateViewDistance, UpdateViewPosition,
 };
 use crate::protocol::{BoundedInt, Nbt};
 use crate::server::ServerPacketChannels;
 use crate::slotmap::{Key, SlotMap};
 use crate::util::{chunks_in_view_distance, is_chunk_in_view_distance};
 use crate::var_int::VarInt;
-use crate::{ident, ChunkPos, Chunks, Entities, EntityId, Server, Text, Ticks, LIBRARY_NAMESPACE};
+use crate::{
+    ident, ChunkPos, Chunks, Entities, EntityId, Server, Text, Ticks, WorldMeta, LIBRARY_NAMESPACE,
+};
 
 pub struct Clients {
     sm: SlotMap<Client>,
@@ -328,7 +332,7 @@ impl<'a> ClientMut<'a> {
         server: &Server,
         entities: &Entities,
         chunks: &Chunks,
-        dimension_id: DimensionId,
+        meta: &WorldMeta,
     ) {
         self.0.events.clear();
 
@@ -347,11 +351,13 @@ impl<'a> ClientMut<'a> {
             return;
         }
 
-        let dimension = server.dimension(dimension_id);
+        let dimension = server.dimension(meta.dimension());
+
+        let current_tick = server.current_tick();
 
         // Send the join game packet and other initial packets. We defer this until now
         // so that the user can set the client's location, game mode, etc.
-        if self.created_tick == server.current_tick() {
+        if self.created_tick == current_tick {
             self.send_packet(JoinGame {
                 entity_id: 0,       // EntityId 0 is reserved for clients.
                 is_hardcore: false, // TODO
@@ -363,7 +369,7 @@ impl<'a> ClientMut<'a> {
                     .collect(),
                 dimension_codec: Nbt(make_dimension_codec(server)),
                 dimension: Nbt(to_dimension_registry_item(dimension)),
-                dimension_name: ident!("{LIBRARY_NAMESPACE}:dimension_{}", dimension_id.0),
+                dimension_name: ident!("{LIBRARY_NAMESPACE}:dimension_{}", meta.dimension().0),
                 hashed_seed: 0,
                 max_players: VarInt(0),
                 view_distance: BoundedInt(VarInt(self.new_max_view_distance as i32)),
@@ -396,7 +402,7 @@ impl<'a> ClientMut<'a> {
         // Update view distance fog on the client if necessary.
         if self.0.old_max_view_distance != self.0.new_max_view_distance {
             self.0.old_max_view_distance = self.0.new_max_view_distance;
-            if self.0.created_tick != server.current_tick() {
+            if self.0.created_tick != current_tick {
                 self.send_packet(UpdateViewDistance {
                     view_distance: BoundedInt(VarInt(self.0.new_max_view_distance as i32)),
                 })
@@ -404,7 +410,7 @@ impl<'a> ClientMut<'a> {
         }
 
         // Check if it's time to send another keepalive.
-        if server.current_tick() % (server.tick_rate() * 8) == 0 {
+        if current_tick % (server.tick_rate() * 8) == 0 {
             if self.0.got_keepalive {
                 let id = rand::random();
                 self.send_packet(KeepAliveClientbound { id });
@@ -451,7 +457,7 @@ impl<'a> ClientMut<'a> {
 
             if let Some(chunk) = chunks.get(pos) {
                 if is_chunk_in_view_distance(center, pos, view_dist + cache)
-                    && chunk.created_tick() != server.current_tick()
+                    && chunk.created_tick() != current_tick
                 {
                     if let Some(pkt) = chunk.block_change_packet(pos) {
                         send_packet(&mut self.0.send, pkt);
@@ -484,7 +490,6 @@ impl<'a> ClientMut<'a> {
 
         // This is done after the chunks are loaded so that the "downloading terrain"
         // screen is closed at the appropriate time.
-
         if self.0.teleported_this_tick {
             self.0.teleported_this_tick = false;
 
@@ -504,10 +509,90 @@ impl<'a> ClientMut<'a> {
         // longer visible.
         self.0.loaded_entities.retain(|&id| {
             if let Some(entity) = entities.get(id) {
-                if self.0.new_position.distance(entity.position()) <= view_dist as f64 * 16.0 {
+                debug_assert!(entity.typ() != EntityType::Marker);
+                if self.0.new_position.distance(entity.position()) <= view_dist as f64 * 16.0
+                    && !entity.flags().type_modified()
+                {
                     if let Some(meta) = entity.updated_metadata_packet(id) {
                         send_packet(&mut self.0.send, meta);
                     }
+
+                    let position_delta = entity.position() - entity.old_position();
+                    let needs_teleport = position_delta.map(f64::abs).reduce_partial_max() >= 8.0;
+                    let flags = entity.flags();
+
+                    if entity.position() != entity.old_position()
+                        && !needs_teleport
+                        && flags.yaw_or_pitch_modified()
+                    {
+                        send_packet(
+                            &mut self.0.send,
+                            EntityPositionAndRotation {
+                                entity_id: VarInt(id.to_network_id()),
+                                delta: (position_delta * 4096.0).as_(),
+                                yaw: ByteAngle::from_degrees(entity.yaw()),
+                                pitch: ByteAngle::from_degrees(entity.pitch()),
+                                on_ground: entity.on_ground(),
+                            },
+                        );
+                    } else {
+                        if entity.position() != entity.old_position() && !needs_teleport {
+                            send_packet(
+                                &mut self.0.send,
+                                EntityPosition {
+                                    entity_id: VarInt(id.to_network_id()),
+                                    delta: (position_delta * 4096.0).as_(),
+                                    on_ground: entity.on_ground(),
+                                },
+                            );
+                        }
+
+                        if flags.yaw_or_pitch_modified() {
+                            send_packet(
+                                &mut self.0.send,
+                                EntityRotation {
+                                    entity_id: VarInt(id.to_network_id()),
+                                    yaw: ByteAngle::from_degrees(entity.yaw()),
+                                    pitch: ByteAngle::from_degrees(entity.pitch()),
+                                    on_ground: entity.on_ground(),
+                                },
+                            );
+                        }
+                    }
+
+                    if needs_teleport {
+                        send_packet(
+                            &mut self.0.send,
+                            EntityTeleport {
+                                entity_id: VarInt(id.to_network_id()),
+                                position: entity.position(),
+                                yaw: ByteAngle::from_degrees(entity.yaw()),
+                                pitch: ByteAngle::from_degrees(entity.pitch()),
+                                on_ground: entity.on_ground(),
+                            },
+                        );
+                    }
+
+                    if flags.velocity_modified() {
+                        send_packet(
+                            &mut self.0.send,
+                            EntityVelocity {
+                                entity_id: VarInt(id.to_network_id()),
+                                velocity: velocity_to_packet_units(entity.velocity()),
+                            },
+                        );
+                    }
+
+                    if flags.head_yaw_modified() {
+                        send_packet(
+                            &mut self.0.send,
+                            EntityHeadLook {
+                                entity_id: VarInt(id.to_network_id()),
+                                head_yaw: ByteAngle::from_degrees(entity.head_yaw()),
+                            },
+                        )
+                    }
+
                     return true;
                 }
             }
@@ -523,6 +608,7 @@ impl<'a> ClientMut<'a> {
         }
 
         // Spawn new entities within the view distance.
+        // TODO: use BVH
         for (id, entity) in entities.iter() {
             if self.position().distance(entity.position()) <= view_dist as f64 * 16.0
                 && entity.typ() != EntityType::Marker

src/entity.rs

@@ -162,7 +162,10 @@ impl<'a> EntitiesMut<'a> {
         for (_, e) in self.iter_mut() {
             e.0.old_position = e.new_position;
             e.0.meta.clear_modifications();
+
+            let on_ground = e.0.flags.on_ground();
             e.0.flags = EntityFlags(0);
+            e.0.flags.set_on_ground(on_ground);
         }
     }
 }
@@ -204,11 +207,12 @@ impl<'a> Deref for EntityMut<'a> {
 /// modified.
 #[bitfield(u8)]
 pub(crate) struct EntityFlags {
-    meta_modified: bool,
+    /// When the type of this entity changes.
-    yaw_or_pitch_modified: bool,
+    pub type_modified: bool,
-    head_yaw_modified: bool,
+    pub yaw_or_pitch_modified: bool,
-    head_pitch_modified: bool,
+    pub head_yaw_modified: bool,
-    velocity_modified: bool,
+    pub velocity_modified: bool,
+    pub on_ground: bool,
     #[bits(3)]
     _pad: u8,
 }
@@ -254,16 +258,15 @@ impl Entity {
         self.head_yaw
     }
 
-    /// Gets the head pitch of this entity (in degrees).
-    pub fn head_pitch(&self) -> f32 {
-        self.head_pitch
-    }
-
     /// Gets the velocity of this entity in meters per second.
     pub fn velocity(&self) -> Vec3<f32> {
         self.velocity
     }
 
+    pub fn on_ground(&self) -> bool {
+        self.flags.on_ground()
+    }
+
     /// Gets the metadata packet to send to clients after this entity has been
     /// spawned.
     ///
@@ -361,7 +364,7 @@ impl Entity {
                     position: self.new_position,
                     yaw: ByteAngle::from_degrees(self.yaw),
                     pitch: ByteAngle::from_degrees(self.pitch),
-                    head_pitch: ByteAngle::from_degrees(self.head_pitch),
+                    head_yaw: ByteAngle::from_degrees(self.head_yaw),
                     velocity: velocity_to_packet_units(self.velocity),
                 }))
             }
@@ -507,7 +510,7 @@ impl Entity {
     }
 }
 
-fn velocity_to_packet_units(vel: Vec3<f32>) -> Vec3<i16> {
+pub(crate) fn velocity_to_packet_units(vel: Vec3<f32>) -> Vec3<i16> {
     // The saturating cast to i16 is desirable.
     (vel * 400.0).as_()
 }
@@ -528,8 +531,8 @@ impl<'a> EntityMut<'a> {
     /// All metadata of this entity is reset to the default values.
     pub fn set_type(&mut self, typ: EntityType) {
         self.0.meta = EntityMeta::new(typ);
-        // All metadata is lost, so we must mark it as modified unconditionally.
+        // All metadata is lost so we must mark it as modified unconditionally.
-        self.0.flags.set_meta_modified(true);
+        self.0.flags.set_type_modified(true);
     }
 
     /// Sets the position of this entity in the world it inhabits.
@@ -539,43 +542,40 @@ impl<'a> EntityMut<'a> {
 
     /// Sets the yaw of this entity (in degrees).
     pub fn set_yaw(&mut self, yaw: f32) {
-        self.0.yaw = yaw;
+        if self.0.yaw != yaw {
-        if ByteAngle::from_degrees(self.yaw) != ByteAngle::from_degrees(yaw) {
+            self.0.yaw = yaw;
             self.0.flags.set_yaw_or_pitch_modified(true);
         }
     }
 
     /// Sets the pitch of this entity (in degrees).
     pub fn set_pitch(&mut self, pitch: f32) {
-        self.0.pitch = pitch;
+        if self.0.pitch != pitch {
-        if ByteAngle::from_degrees(self.pitch) != ByteAngle::from_degrees(pitch) {
+            self.0.pitch = pitch;
             self.0.flags.set_yaw_or_pitch_modified(true);
         }
     }
 
     /// Sets the head yaw of this entity (in degrees).
     pub fn set_head_yaw(&mut self, head_yaw: f32) {
-        self.0.head_yaw = head_yaw;
+        if self.0.head_yaw != head_yaw {
-        if ByteAngle::from_degrees(self.head_yaw) != ByteAngle::from_degrees(head_yaw) {
+            self.0.head_yaw = head_yaw;
             self.0.flags.set_head_yaw_modified(true);
         }
     }
 
-    /// Sets the head pitch of this entity (in degrees).
-    pub fn set_head_pitch(&mut self, head_pitch: f32) {
-        self.0.head_pitch = head_pitch;
-        if ByteAngle::from_degrees(self.head_pitch) != ByteAngle::from_degrees(head_pitch) {
-            self.0.flags.set_head_pitch_modified(true);
-        }
-    }
-
     pub fn set_velocity(&mut self, velocity: impl Into<Vec3<f32>>) {
         let new_vel = velocity.into();
-        self.0.velocity = new_vel;
+
-        if velocity_to_packet_units(self.velocity) != velocity_to_packet_units(new_vel) {
+        if self.0.velocity != new_vel {
+            self.0.velocity = new_vel;
             self.0.flags.set_velocity_modified(true);
         }
     }
+
+    pub fn set_on_ground(&mut self, on_ground: bool) {
+        self.0.flags.set_on_ground(on_ground);
+    }
 }
 
 pub(crate) enum EntitySpawnPacket {

src/lib.rs

@@ -36,7 +36,7 @@ pub use identifier::Identifier;
 pub use server::{start_server, NewClientData, Server, ShutdownResult};
 pub use text::{Text, TextFormat};
 pub use uuid::Uuid;
-pub use world::{WorldId, WorldMut, WorldRef, Worlds, WorldsMut};
+pub use world::{WorldId, WorldMeta, WorldMetaMut, WorldMut, WorldRef, Worlds, WorldsMut};
 pub use {nbt, uuid, vek};
 
 /// The Minecraft protocol version that this library targets.

src/packets.rs

@@ -13,7 +13,7 @@ use num::{One, Zero};
 use paste::paste;
 use serde::{Deserialize, Serialize};
 use uuid::Uuid;
-use vek::{Vec2, Vec3};
+use vek::Vec3;
 
 use crate::block_pos::BlockPos;
 use crate::byte_angle::ByteAngle;
@@ -469,7 +469,7 @@ pub mod play {
             position: Vec3<f64>,
             yaw: ByteAngle,
             pitch: ByteAngle,
-            head_pitch: ByteAngle,
+            head_yaw: ByteAngle,
             velocity: Vec3<i16>,
         }
     }
@@ -964,6 +964,33 @@ pub mod play {
         }
     }
 
+    def_struct! {
+        EntityPosition 0x29 {
+            entity_id: VarInt,
+            delta: Vec3<i16>,
+            on_ground: bool,
+        }
+    }
+
+    def_struct! {
+        EntityPositionAndRotation 0x2a {
+            entity_id: VarInt,
+            delta: Vec3<i16>,
+            yaw: ByteAngle,
+            pitch: ByteAngle,
+            on_ground: bool,
+        }
+    }
+
+    def_struct! {
+        EntityRotation 0x2b {
+            entity_id: VarInt,
+            yaw: ByteAngle,
+            pitch: ByteAngle,
+            on_ground: bool,
+        }
+    }
+
     def_struct! {
         PlayerPositionAndLook 0x38 {
             position: Vec3<f64>,
@@ -991,6 +1018,13 @@ pub mod play {
         }
     }
 
+    def_struct! {
+        EntityHeadLook 0x3e {
+            entity_id: VarInt,
+            head_yaw: ByteAngle,
+        }
+    }
+
     def_struct! {
         MultiBlockChange 0x3f {
             chunk_section_position: u64,
@@ -1032,6 +1066,13 @@ pub mod play {
         }
     }
 
+    def_struct! {
+        EntityVelocity 0x4f {
+            entity_id: VarInt,
+            velocity: Vec3<i16>,
+        }
+    }
+
     def_struct! {
         TimeUpdate 0x59 {
             /// The age of the world in 1/20ths of a second.
@@ -1043,6 +1084,16 @@ pub mod play {
         }
     }
 
+    def_struct! {
+        EntityTeleport 0x62 {
+            entity_id: VarInt,
+            position: Vec3<f64>,
+            yaw: ByteAngle,
+            pitch: ByteAngle,
+            on_ground: bool,
+        }
+    }
+
     macro_rules! def_client_play_packet_enum {
         {
             $($packet:ident),* $(,)?
@@ -1115,14 +1166,20 @@ pub mod play {
         KeepAliveClientbound,
         ChunkDataAndUpdateLight,
         JoinGame,
+        EntityPosition,
+        EntityPositionAndRotation,
+        EntityRotation,
         PlayerPositionAndLook,
         DestroyEntities,
+        EntityHeadLook,
         MultiBlockChange,
         HeldItemChangeClientbound,
         UpdateViewPosition,
         UpdateViewDistance,
         SpawnPosition,
         EntityMetadata,
+        EntityVelocity,
+        EntityTeleport,
         TimeUpdate,
     }
 

src/server.rs

@@ -368,7 +368,12 @@ fn do_update_loop(server: Server, mut worlds: WorldsMut) -> ShutdownResult {
             });
 
             world.clients.par_iter_mut().for_each(|(_, mut client)| {
-                client.update(&server, &world.entities, &world.chunks, world.dimension);
+                client.update(
+                    &server,
+                    &world.entities,
+                    &world.chunks,
+                    &world.meta,
+                );
             });
 
             world.entities.update();

src/world.rs

@@ -1,15 +1,11 @@
-use std::collections::{HashMap, HashSet};
 use std::iter::FusedIterator;
 use std::ops::Deref;
 
-use rayon::iter::{IntoParallelRefIterator, ParallelIterator};
+use rayon::iter::ParallelIterator;
 
-use crate::chunk::ChunkPos;
 use crate::config::DimensionId;
 use crate::slotmap::{Key, SlotMap};
-use crate::{
+use crate::{Chunks, ChunksMut, Clients, ClientsMut, Entities, EntitiesMut, Server};
-    Chunks, ChunksMut, Clients, ClientsMut, Entities, EntitiesMut, Entity, EntityId, Server,
-};
 
 pub struct Worlds {
     sm: SlotMap<World>,
@@ -67,7 +63,10 @@ impl<'a> WorldsMut<'a> {
                 self.server.clone(),
                 (self.server.dimension(dim).height / 16) as u32,
             ),
-            dimension: dim,
+            meta: WorldMeta {
+                dimension: dim,
+                is_flat: false,
+            },
         }))
     }
 
@@ -123,7 +122,7 @@ pub(crate) struct World {
     clients: Clients,
     entities: Entities,
     chunks: Chunks,
-    dimension: DimensionId,
+    meta: WorldMeta,
 }
 
 /// A bag of immutable references to the components of a world.
@@ -131,7 +130,7 @@ pub struct WorldRef<'a> {
     pub clients: &'a Clients,
     pub entities: &'a Entities,
     pub chunks: &'a Chunks,
-    pub dimension: DimensionId,
+    pub meta: &'a WorldMeta,
 }
 
 impl<'a> WorldRef<'a> {
@@ -140,7 +139,7 @@ impl<'a> WorldRef<'a> {
             clients: &w.clients,
             entities: &w.entities,
             chunks: &w.chunks,
-            dimension: w.dimension,
+            meta: &w.meta,
         }
     }
 }
@@ -150,7 +149,7 @@ pub struct WorldMut<'a> {
     pub clients: ClientsMut<'a>,
     pub entities: EntitiesMut<'a>,
     pub chunks: ChunksMut<'a>,
-    pub dimension: DimensionId,
+    pub meta: WorldMetaMut<'a>,
 }
 
 impl<'a> WorldMut<'a> {
@@ -159,7 +158,7 @@ impl<'a> WorldMut<'a> {
             clients: ClientsMut::new(&mut w.clients),
             entities: EntitiesMut::new(&mut w.entities),
             chunks: ChunksMut::new(&mut w.chunks),
-            dimension: w.dimension,
+            meta: WorldMetaMut(&mut w.meta),
         }
     }
 
@@ -168,7 +167,38 @@ impl<'a> WorldMut<'a> {
             clients: &self.clients,
             entities: &self.entities,
             chunks: &self.chunks,
-            dimension: self.dimension,
+            meta: &self.meta,
         }
     }
 }
+
+pub struct WorldMeta {
+    dimension: DimensionId,
+    is_flat: bool,
+}
+
+impl WorldMeta {
+    pub fn dimension(&self) -> DimensionId {
+        self.dimension
+    }
+
+    pub fn is_flat(&self) -> bool {
+        self.is_flat
+    }
+}
+
+pub struct WorldMetaMut<'a>(&'a mut WorldMeta);
+
+impl<'a> Deref for WorldMetaMut<'a> {
+    type Target = WorldMeta;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl<'a> WorldMetaMut<'a> {
+    pub fn set_flat(&mut self, flat: bool) {
+        self.0.is_flat = flat;
+    }
+}