Add distance-based LOD for voxel chunks

client/src/plugins/environment/environment_plugin.rs

@@ -4,7 +4,9 @@ use crate::plugins::environment::systems::voxels::culling::{despawn_distant_chun
 use crate::plugins::environment::systems::voxels::debug::{draw_grid, visualize_octree_system};
 use crate::plugins::environment::systems::voxels::queue_systems;
 use crate::plugins::environment::systems::voxels::queue_systems::{enqueue_visible_chunks, process_chunk_queue};
+                    update_chunk_lods.after(process_chunk_queue),
 use crate::plugins::environment::systems::voxels::render_chunks::rebuild_dirty_chunks;
+use crate::plugins::environment::systems::voxels::lod::update_chunk_lods;
 use crate::plugins::environment::systems::voxels::structure::{ChunkBudget, ChunkCullingCfg, ChunkQueue, SparseVoxelOctree, SpawnedChunks};
 
 pub struct EnvironmentPlugin;
@@ -40,6 +42,7 @@ impl Plugin for EnvironmentPlugin {
                     despawn_distant_chunks,                       // 1.  remove too-far chunks
                     enqueue_visible_chunks.after(despawn_distant_chunks),         // 2.  find new visible ones
                     process_chunk_queue .after(enqueue_visible_chunks),           // 3.  spawn ≤ budget per frame
+                    update_chunk_lods.after(process_chunk_queue),
                     rebuild_dirty_chunks .after(process_chunk_queue),             // 4.  (re)mesh dirty chunks
 
                     /* ---------- optional debug drawing ------- */

client/src/plugins/environment/systems/voxels/helper.rs

@@ -269,6 +269,16 @@ pub fn world_to_chunk(tree: &SparseVoxelOctree, p: Vec3) -> ChunkKey {
     )
 }
 
+pub fn chunk_center_world(tree: &SparseVoxelOctree, key: ChunkKey) -> Vec3 {
+    let half = tree.size * 0.5;
+    let step = tree.get_spacing_at_depth(tree.max_depth);
+    Vec3::new(
+        (key.0 as f32 + 0.5) * CHUNK_SIZE as f32 * step - half,
+        (key.1 as f32 + 0.5) * CHUNK_SIZE as f32 * step - half,
+        (key.2 as f32 + 0.5) * CHUNK_SIZE as f32 * step - half,
+    )
+}
+
 impl AABB {
     pub fn intersects_aabb(&self, other: &AABB) -> bool {
         self.min.x <= other.max.x &&

client/src/plugins/environment/systems/voxels/lod.rs

@@ -0,0 +1,42 @@
+use bevy::prelude::*;
+use crate::plugins::environment::systems::voxels::helper::chunk_center_world;
+use crate::plugins::environment::systems::voxels::structure::{Chunk, ChunkLod, ChunkCullingCfg, SparseVoxelOctree};
+
+/// Update each chunk's LOD level based on its distance from the camera.
+/// Chunks farther away get a higher LOD value (coarser mesh).
+pub fn update_chunk_lods(
+    cam_q: Query<&GlobalTransform, With<Camera>>,
+    mut chunks: Query<(&Chunk, &mut ChunkLod)>,
+    mut tree_q: Query<&mut SparseVoxelOctree>,
+    cfg: Res<ChunkCullingCfg>,
+) {
+    let cam_pos = cam_q.single().translation();
+    let max_depth;
+    let range_step;
+    {
+        let tree = tree_q.single();
+        max_depth = tree.max_depth;
+        range_step = cfg.view_distance_chunks as f32 / max_depth as f32;
+    }
+
+    let mut changed = Vec::new();
+    for (chunk, mut lod) in chunks.iter_mut() {
+        let tree = tree_q.single();
+        let center = chunk_center_world(&tree, chunk.key);
+        let dist_chunks = cam_pos.distance(center)
+            / (cfg.view_distance_chunks as f32);
+        let mut level = (dist_chunks / range_step).floor() as u32;
+        if level > max_depth { level = max_depth; }
+        if lod.0 != level {
+            lod.0 = level;
+            changed.push(chunk.key);
+        }
+    }
+
+    if !changed.is_empty() {
+        let mut tree = tree_q.single_mut();
+        for key in changed {
+            tree.dirty_chunks.insert(key);
+        }
+    }
+}

client/src/plugins/environment/systems/voxels/mod.rs

@@ -8,3 +8,4 @@ mod meshing;
 pub mod render_chunks;
 pub mod culling;
 pub mod queue_systems;
+pub mod lod;

client/src/plugins/environment/systems/voxels/render_chunks.rs

@@ -18,15 +18,16 @@ pub fn rebuild_dirty_chunks(
     chunk_q      : Query<(Entity,
                           &Chunk,
                           &Mesh3d,
-                          &MeshMaterial3d<StandardMaterial>)>,
+                          &MeshMaterial3d<StandardMaterial>,
+                          &ChunkLod)>,
     mut spawned  : ResMut<SpawnedChunks>,
     root         : Res<RootGrid>,
 ) {
     // map ChunkKey → (entity, mesh-handle, material-handle)
-    let existing: HashMap<ChunkKey, (Entity, Handle<Mesh>, Handle<StandardMaterial>)> =
+    let existing: HashMap<ChunkKey, (Entity, Handle<Mesh>, Handle<StandardMaterial>, u32)> =
         chunk_q
             .iter()
-            .map(|(e, c, m, mat)| (c.key, (e, m.0.clone(), mat.0.clone())))
+            .map(|(e, c, m, mat, lod)| (c.key, (e, m.0.clone(), mat.0.clone(), lod.0)))
             .collect();
 
     for mut tree in &mut octrees {
@@ -37,6 +38,7 @@ pub fn rebuild_dirty_chunks(
         //------------------------------------------------ collect voxel data
         let mut bufs = Vec::new();
         for key in tree.dirty_chunks.iter().copied() {
+            let lod = existing.get(&key).map(|v| v.3).unwrap_or(0);
             let mut buf =
                 [[[None; CHUNK_SIZE as usize]; CHUNK_SIZE as usize]; CHUNK_SIZE as usize];
 
@@ -48,24 +50,40 @@ pub fn rebuild_dirty_chunks(
                 key.2 as f32 * CHUNK_SIZE as f32 * step - half,
             );
 
-            for lx in 0..CHUNK_SIZE {
-                for ly in 0..CHUNK_SIZE {
-                    for lz in 0..CHUNK_SIZE {
-                        let world = origin
-                            + Vec3::new(lx as f32 * step, ly as f32 * step, lz as f32 * step);
-                        if let Some(v) = tree.get_voxel_at_world_coords(world) {
-                            buf[lx as usize][ly as usize][lz as usize] = Some(*v);
+            let mult = 1 << lod;
+            for gx in (0..CHUNK_SIZE).step_by(mult as usize) {
+                for gy in (0..CHUNK_SIZE).step_by(mult as usize) {
+                    for gz in (0..CHUNK_SIZE).step_by(mult as usize) {
+                        let center = origin
+                            + Vec3::new(
+                                (gx + mult / 2) as f32 * step,
+                                (gy + mult / 2) as f32 * step,
+                                (gz + mult / 2) as f32 * step,
+                            );
+                        if let Some(v) = tree.get_voxel_at_world_coords(center) {
+                            for lx in 0..mult {
+                                for ly in 0..mult {
+                                    for lz in 0..mult {
+                                        let ix = gx + lx;
+                                        let iy = gy + ly;
+                                        let iz = gz + lz;
+                                        if ix < CHUNK_SIZE && iy < CHUNK_SIZE && iz < CHUNK_SIZE {
+                                            buf[ix as usize][iy as usize][iz as usize] = Some(*v);
+                                        }
+                                    }
+                                }
+                            }
                         }
                     }
                 }
             }
 
-            bufs.push((key, buf, origin, step));
+            bufs.push((key, buf, origin, step, lod));
         }
 
         //------------------------------------------------ create / update
-        for (key, buf, origin, step) in bufs {
-            if let Some((ent, mesh_h, _mat_h)) = existing.get(&key).cloned() {
+        for (key, buf, origin, step, lod) in bufs {
+            if let Some((ent, mesh_h, _mat_h, _)) = existing.get(&key).cloned() {
                 // update mesh in-place; keeps old asset id
                 if let Some(mesh) = meshes.get_mut(&mesh_h) {
                     *mesh = mesh_chunk(&buf, origin, step, &tree);
@@ -84,6 +102,7 @@ pub fn rebuild_dirty_chunks(
                             Transform::default(),
                             GridCell::<i64>::ZERO,
                             Chunk { key, voxels: Vec::new(), dirty: false },
+                            ChunkLod(lod),
                             /*Wireframe,*/
                         ))
                         .id();

client/src/plugins/environment/systems/voxels/structure.rs

@@ -96,6 +96,9 @@ pub struct Chunk {
 
 }
 
+#[derive(Component, Debug, Clone, Copy)]
+pub struct ChunkLod(pub u32);
+
 
 #[derive(Debug, Clone, Copy, Hash, PartialEq, Eq)]
 pub struct ChunkKey(pub i32, pub i32, pub i32);