Direct bits per idx for biomes depends on the size of the biome registry

src/chunk.rs

@@ -27,15 +27,18 @@ use crate::Ticks;
 /// A container for all [`Chunks`]s in a [`World`](crate::world::World).
 pub struct Chunks<C: Config> {
     chunks: HashMap<ChunkPos, Chunk<C>>,
-    server: SharedServer<C>,
+    shared: SharedServer<C>,
     dimension: DimensionId,
 }
 
 impl<C: Config> Chunks<C> {
-    pub(crate) fn new(server: SharedServer<C>, dimension: DimensionId) -> Self {
+    pub(crate) fn new(
+        shared: SharedServer<C>,
+        dimension: DimensionId,
+    ) -> Self {
         Self {
             chunks: HashMap::new(),
-            server,
+            shared,
             dimension,
         }
     }
@@ -51,8 +54,14 @@ impl<C: Config> Chunks<C> {
     /// are not spawned within unloaded chunks via
     /// [`spawn`](crate::client::Client::spawn).
     pub fn insert(&mut self, pos: impl Into<ChunkPos>, state: C::ChunkState) -> &mut Chunk<C> {
-        let section_count = (self.server.dimension(self.dimension).height / 16) as u32;
-        let chunk = Chunk::new(section_count, self.server.current_tick(), state);
+        let section_count = (self.shared.dimension(self.dimension).height / 16) as u32;
+        let biome_registry_len = self.shared.biomes().len();
+        let chunk = Chunk::new(
+            section_count,
+            self.shared.current_tick(),
+            biome_registry_len,
+            state,
+        );
 
         match self.chunks.entry(pos.into()) {
             Entry::Occupied(mut oe) => {
@@ -140,7 +149,7 @@ impl<C: Config> Chunks<C> {
 
         let chunk = self.get(chunk_pos)?;
 
-        let min_y = self.server.dimension(self.dimension).min_y;
+        let min_y = self.shared.dimension(self.dimension).min_y;
 
         let y = pos.y.checked_sub(min_y)?.try_into().ok()?;
 
@@ -168,7 +177,7 @@ impl<C: Config> Chunks<C> {
         let chunk_pos = ChunkPos::from(pos);
 
         if let Some(chunk) = self.chunks.get_mut(&chunk_pos) {
-            let min_y = self.server.dimension(self.dimension).min_y;
+            let min_y = self.shared.dimension(self.dimension).min_y;
 
             if let Some(y) = pos.y.checked_sub(min_y).and_then(|y| y.try_into().ok()) {
                 if y < chunk.height() {
@@ -203,7 +212,12 @@ pub struct Chunk<C: Config> {
 }
 
 impl<C: Config> Chunk<C> {
-    pub(crate) fn new(section_count: u32, current_tick: Ticks, data: C::ChunkState) -> Self {
+    pub(crate) fn new(
+        section_count: u32,
+        current_tick: Ticks,
+        biome_registry_len: usize,
+        data: C::ChunkState,
+    ) -> Self {
         let sect = ChunkSection {
             blocks: [BlockState::AIR.to_raw(); 4096],
             modified_count: 1, // Must be >0 so the chunk is initialized.
@@ -218,7 +232,7 @@ impl<C: Config> Chunk<C> {
             created_tick: current_tick,
         };
 
-        chunk.apply_modifications();
+        chunk.apply_modifications(biome_registry_len);
         chunk
     }
 
@@ -363,7 +377,7 @@ impl<C: Config> Chunk<C> {
         }
     }
 
-    pub(crate) fn apply_modifications(&mut self) {
+    pub(crate) fn apply_modifications(&mut self, biome_registry_len: usize) {
         let mut any_modified = false;
 
         for sect in self.sections.iter_mut() {
@@ -388,18 +402,16 @@ impl<C: Config> Chunk<C> {
                     sect.blocks.iter().cloned(),
                     4,
                     9,
-                    log2_ceil((BlockState::max_raw() + 1) as usize),
+                    log2_ceil(BlockState::max_raw() as usize),
                     &mut sect.compact_data,
                 )
                 .unwrap();
 
-                // TODO: The direct bits per idx changes depending on the number of biomes in
-                // the biome registry.
                 encode_paletted_container(
                     sect.biomes.iter().map(|b| b.0),
                     0,
                     4,
-                    6,
+                    log2_ceil(biome_registry_len),
                     &mut sect.compact_data,
                 )
                 .unwrap();
@@ -557,5 +569,6 @@ fn encode_paletted_container(
 
 /// Calculates the log base 2 rounded up.
 fn log2_ceil(n: usize) -> usize {
+    debug_assert_ne!(n, 0);
     n.next_power_of_two().trailing_zeros() as usize
 }

src/server.rs

@@ -441,7 +441,7 @@ fn do_update_loop<C: Config>(server: &mut Server<C>) -> ShutdownResult {
                     // Chunks created this tick can have their changes applied immediately because
                     // they have not been observed by clients yet. Clients will not have to be sent
                     // the block change packet in this case.
-                    chunk.apply_modifications();
+                    chunk.apply_modifications(server.shared.biomes().len());
                 }
             });
 
@@ -461,7 +461,7 @@ fn do_update_loop<C: Config>(server: &mut Server<C>) -> ShutdownResult {
 
         server.worlds.par_iter_mut().for_each(|(_, world)| {
             world.chunks.par_iter_mut().for_each(|(_, chunk)| {
-                chunk.apply_modifications();
+                chunk.apply_modifications(server.shared.biomes().len());
             });
         });
 

src/world.rs

@@ -14,7 +14,7 @@ use crate::spatial_index::SpatialIndex;
 /// A container for all [`World`]s on a [`Server`](crate::server::Server).
 pub struct Worlds<C: Config> {
     slab: VersionedSlab<World<C>>,
-    server: SharedServer<C>,
+    shared: SharedServer<C>,
 }
 
 /// An identifier for a [`World`] on the server.
@@ -35,10 +35,10 @@ impl WorldId {
 }
 
 impl<C: Config> Worlds<C> {
-    pub(crate) fn new(server: SharedServer<C>) -> Self {
+    pub(crate) fn new(shared: SharedServer<C>) -> Self {
         Self {
             slab: VersionedSlab::new(),
-            server,
+            shared,
         }
     }
 
@@ -48,7 +48,7 @@ impl<C: Config> Worlds<C> {
         let (id, world) = self.slab.insert(World {
             state,
             spatial_index: SpatialIndex::new(),
-            chunks: Chunks::new(self.server.clone(), dim),
+            chunks: Chunks::new(self.shared.clone(), dim),
             meta: WorldMeta { dimension: dim },
         });