quilted chunk optimisations

src/world/tiles/rendering.rs

@@ -1,5 +1,5 @@
 use bevy::{asset::RenderAssetUsages, prelude::*, render::render_resource};
-use bevy_platform::collections::HashMap;
+use bevy_platform::collections::{HashMap, HashSet};
 use bevy_platform::sync::Mutex;
 use bevy_platform::time::Instant;
 use rayon::prelude::*;
@@ -9,6 +9,11 @@ use crate::{
     world::{tiles::FloorTile, TextureIDs, Textures, Z_BELOW, Z_TOTAL},
 };
 
+/// Side length of a spatial chunk in tiles.
+/// 32 tiles × TILE_PIXELS px = 512 px texture (GPU-friendly power-of-two).
+/// Tune this constant to balance draw calls vs. rebake granularity.
+pub const CHUNK_TILES: i32 = 32;
+
 #[derive(Debug, PartialEq)]
 pub enum TerrainSpriteState {
     Inactive,
@@ -24,20 +29,52 @@ pub struct CurrentWorldSpriteState {
 
 #[derive(Component)]
 pub struct TerrainSprite {
-    pub z_index: usize, // Store the z-index this sprite belongs to (as world_Z)
+    /// Chunk grid coordinate and z-level this sprite covers.
+    pub key: ChunkZKey,
+}
+
+/// Uniquely identifies one spatial chunk at one z-level.
+/// Used as a HashMap / HashSet key throughout the bake pipeline.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct ChunkZKey {
+    pub chunk_x: i32,
+    pub chunk_y: i32,
+    pub z_index: usize,
+}
+
+impl ChunkZKey {
+    #[inline]
+    fn from_world(world_x: f32, world_y: f32, z_index: usize) -> Self {
+        Self {
+            chunk_x: (world_x / (TILE_SIZE * CHUNK_TILES as f32)).floor() as i32,
+            chunk_y: (world_y / (TILE_SIZE * CHUNK_TILES as f32)).floor() as i32,
+            z_index,
+        }
+    }
 }
 
 #[derive(Resource)]
 pub struct QuiltCache {
-    pub dimensions: HashMap<usize, (u32, u32)>,
+    /// Pixel dimensions (w, h) of the last-baked texture for each chunk×z.
-    pub dirty_indices: Vec<usize>,
+    pub dimensions: HashMap<ChunkZKey, (u32, u32)>,
+
+    /// Which chunk×z combinations need to be rebaked on the next bake pass.
+    /// Insert here whenever a tile edit occurs.
+    /// Cleared after every full bake; ignored during partial (dirty-only) bakes.
+    pub dirty_keys: HashSet<ChunkZKey>,
+
+    /// Reusable pixel buffers keyed by ChunkZKey.
+    /// Zeroed and reused when dimensions are unchanged; reallocated on resize.
+    /// Buffers for chunks with no remaining tiles are dropped automatically.
+    pub pixel_buffers: HashMap<ChunkZKey, Vec<u8>>,
 }
 
 impl Default for QuiltCache {
     fn default() -> Self {
         Self {
             dimensions: HashMap::new(),
-            dirty_indices: Vec::new(),
+            dirty_keys: HashSet::new(),
+            pixel_buffers: HashMap::new(),
         }
     }
 }
@@ -49,7 +86,7 @@ pub fn build_quilted_terrain_sprites(
     mut cwss: ResMut<CurrentWorldSpriteState>,
     textures: Res<Textures>,
     texture_ids: Res<TextureIDs>,
-    query_terrain_sprites: Query<Entity, With<TerrainSprite>>,
+    query_terrain_sprites: Query<(Entity, &TerrainSprite)>,
     mut images: ResMut<Assets<Image>>,
     mut quilt_cache: ResMut<QuiltCache>,
 ) {
@@ -59,127 +96,196 @@ pub fn build_quilted_terrain_sprites(
     let now = Instant::now();
     cwss.state = TerrainSpriteState::InProgress;
 
-    // Despawn existing terrain sprites
+    // --- Determine whether this is a full or partial (dirty-only) bake ---
-    let despawn_entities: Vec<Entity> = query_terrain_sprites.iter().collect();
+    //
-    for entity in despawn_entities {
+    // A full bake (dirty_keys is empty) rebuilds every chunk×z from scratch —
+    // used on initial load or after a world reload.
+    // A partial bake only processes the chunk×z entries listed in dirty_keys,
+    // leaving all other sprites untouched. This makes incremental tile edits
+    // proportional to the number of changed chunks, not total world size.
+    let full_bake = quilt_cache.dirty_keys.is_empty();
+
+    // --- Pre-extract texture data on the main thread ---
+    //
+    // Reads Assets<Image> once here, safely, before the rayon parallel section.
+    // Deduplicates lookups (many tiles share textures) and produces an owned
+    // HashMap that is freely shareable across threads without any locking.
+    let mut tile_texture_data: HashMap<u32, (Vec<u8>, u32, u32)> = HashMap::new();
+    for (floortile, _) in query_tiles.iter() {
+        if tile_texture_data.contains_key(&floortile.id) {
+            continue;
+        }
+        let Some(texture_id) = texture_ids.refs.get(&floortile.id) else {
+            continue;
+        };
+        let Some(texture) = textures.handles.get(texture_id) else {
+            continue;
+        };
+        let Some(img) = images.get(texture) else {
+            continue;
+        };
+        let Some(data) = &img.data else {
+            continue;
+        };
+        tile_texture_data.insert(
+            floortile.id,
+            (data.clone(), img.size().x as u32, img.size().y as u32),
+        );
+    }
+
+    // --- Bucket tiles into (chunk_x, chunk_y, z_index) keys ---
+    //
+    // Set-bit iteration means each tile only touches as many buckets as z-levels
+    // it is actually visible at — not Z_TOTAL iterations every time.
+    let mut tiles_by_chunk_z: HashMap<ChunkZKey, Vec<(Vec2, &FloorTile)>> = HashMap::new();
+
+    for (floortile, transform) in query_tiles.iter() {
+        let position = Vec2::new(transform.translation.x, transform.translation.y);
+
+        for (word_idx, &word) in floortile.visible_range.iter().enumerate() {
+            let mut bits = word;
+            while bits != 0 {
+                let bit_pos = bits.trailing_zeros() as usize;
+                let z_index = word_idx * 32 + bit_pos;
+
+                if z_index <= Z_TOTAL as usize {
+                    let key = ChunkZKey::from_world(position.x, position.y, z_index);
+                    tiles_by_chunk_z
+                        .entry(key)
+                        .or_default()
+                        .push((position, floortile));
+                }
+
+                bits &= bits - 1;
+            }
+        }
+    }
+
+    // --- Decide which keys to actually bake this frame ---
+    //
+    // Full bake  → all keys that have tiles.
+    // Dirty bake → only the intersection of dirty_keys and keys that have tiles.
+    //              Keys in dirty_keys that have no tiles are stale deletions;
+    //              their sprites will be despawned below.
+    let keys_to_bake: Vec<ChunkZKey> = if full_bake {
+        tiles_by_chunk_z.keys().cloned().collect()
+    } else {
+        tiles_by_chunk_z
+            .keys()
+            .filter(|k| quilt_cache.dirty_keys.contains(*k))
+            .cloned()
+            .collect()
+    };
+
+    // --- Despawn sprites that need rebuilding ---
+    //
+    // On a full bake, despawn everything.
+    // On a partial bake, despawn only the sprites for dirty chunk×z keys so the
+    // rest of the world remains visible without flickering.
+    for (entity, terrain_sprite) in query_terrain_sprites.iter() {
+        let should_despawn = full_bake || quilt_cache.dirty_keys.contains(&terrain_sprite.key);
+        if should_despawn {
             commands.command_scope(|mut cmd| {
                 cmd.entity(entity).despawn();
             });
         }
-
-    // Collect tiles by z-index first
-    let mut tiles_by_z: HashMap<usize, Vec<(Vec2, &FloorTile)>> = HashMap::new();
-
-    // Calculate bounds for all visible tiles
-    for (floortile, transform) in query_tiles.iter() {
-        let position = Vec2::new(transform.translation.x, transform.translation.y);
-
-        for z_index in 0..=Z_TOTAL as usize {
-            if (floortile.visible_range[z_index / 32] & (1 << (z_index % 32) as u32)) != 0 {
-                tiles_by_z
-                    .entry(z_index)
-                    .or_default()
-                    .push((position, floortile));
-            }
-        }
     }
 
-    // Thread-safe collections to store results
+    // Move pixel buffers out of the cache so rayon threads can borrow from the pool.
-    let dimensions_mutex = Mutex::new(HashMap::new());
+    let buffer_pool: Mutex<HashMap<ChunkZKey, Vec<u8>>> =
-    let texture_handles_mutex = Mutex::new(HashMap::new());
+        Mutex::new(std::mem::take(&mut quilt_cache.pixel_buffers));
 
-    // Process each z-level in parallel
+    let texture_results: Mutex<Vec<(ChunkZKey, Image, f32, f32)>> =
-    let z_indices: Vec<usize> = tiles_by_z.keys().cloned().collect();
+        Mutex::new(Vec::with_capacity(keys_to_bake.len()));
+    let dimensions_results: Mutex<Vec<(ChunkZKey, (u32, u32))>> =
+        Mutex::new(Vec::with_capacity(keys_to_bake.len()));
 
-    z_indices.into_par_iter().for_each(|z_index| {
+    let tile_texture_data = &tile_texture_data;
-        let tiles = if let Some(tiles) = tiles_by_z.get(&z_index) {
+
-            tiles
+    // --- Parallel bake over chunk×z keys ---
-        } else {
+    keys_to_bake.into_par_iter().for_each(|key| {
-            return; // Skip empty z-levels
+        let tiles = match tiles_by_chunk_z.get(&key) {
+            Some(t) if !t.is_empty() => t,
+            _ => return,
         };
 
-        if tiles.is_empty() {
+        // Bounds are clamped to the chunk grid so textures are always exactly
-            return;
+        // CHUNK_TILES wide/tall (or smaller at world edges), keeping sizes
-        }
+        // predictable and buffer reuse rates high.
+        let chunk_world_min_x = key.chunk_x as f32 * TILE_SIZE * CHUNK_TILES as f32;
+        let chunk_world_min_y = key.chunk_y as f32 * TILE_SIZE * CHUNK_TILES as f32;
 
-        // Calculate bounds
+        // Actual tile extent within this chunk (may be smaller than full chunk
-        let min_x_aligned: f32 = ((tiles.iter().map(|(pos, _)| pos.x).reduce(f32::min).unwrap()
+        // at world edges or sparse z-levels).
+        let min_x_aligned: f32 = ((tiles.iter().map(|(p, _)| p.x).reduce(f32::min).unwrap()
             - TILE_SIZE / 2.0)
             / TILE_SIZE)
             .floor()
             * TILE_SIZE;
-        let min_y_aligned: f32 = ((tiles.iter().map(|(pos, _)| pos.y).reduce(f32::min).unwrap()
+        let min_y_aligned: f32 = ((tiles.iter().map(|(p, _)| p.y).reduce(f32::min).unwrap()
             - TILE_SIZE / 2.0)
             / TILE_SIZE)
             .floor()
             * TILE_SIZE;
-        let max_x_aligned: f32 = ((tiles.iter().map(|(pos, _)| pos.x).reduce(f32::max).unwrap()
+        let max_x_aligned: f32 = ((tiles.iter().map(|(p, _)| p.x).reduce(f32::max).unwrap()
             + TILE_SIZE / 2.0)
             / TILE_SIZE)
             .ceil()
             * TILE_SIZE;
-        let max_y_aligned: f32 = ((tiles.iter().map(|(pos, _)| pos.y).reduce(f32::max).unwrap()
+        let max_y_aligned: f32 = ((tiles.iter().map(|(p, _)| p.y).reduce(f32::max).unwrap()
             + TILE_SIZE / 2.0)
             / TILE_SIZE)
             .ceil()
             * TILE_SIZE;
 
-        // Calculate terrain texture dimensions in pixels
         let width_tiles = ((max_x_aligned - min_x_aligned) / TILE_SIZE) as u32;
         let height_tiles = ((max_y_aligned - min_y_aligned) / TILE_SIZE) as u32;
         let width_px = width_tiles * TILE_PIXELS;
         let height_px = height_tiles * TILE_PIXELS;
+        let required_len = (width_px * height_px * 4) as usize;
 
-        // Store dimensions in our thread-safe map
+        dimensions_results
-        dimensions_mutex
             .lock()
             .unwrap()
-            .insert(z_index, (width_px, height_px));
+            .push((key, (width_px, height_px)));
 
-        let mut texture_data = vec![0u8; (width_px * height_px * 4) as usize];
+        // Reuse buffer if dimensions match; reallocate only on resize.
+        let mut texture_data = {
+            let mut pool = buffer_pool.lock().unwrap();
+            match pool.remove(&key) {
+                Some(mut buf) if buf.len() == required_len => {
+                    buf.fill(0);
+                    buf
+                }
+                _ => vec![0u8; required_len],
+            }
+        };
 
-        // Process tiles for this z-level
-        // We can't parallelize this inner loop without more complex locking on texture_data
         for (pos, floortile) in tiles {
-            if let Some(texture_id) = texture_ids.refs.get(&floortile.id) {
+            let Some((source, src_width, src_height)) = tile_texture_data.get(&floortile.id) else {
-                if let Some(texture) = textures.handles.get(texture_id) {
+                continue;
+            };
+            let src_width = *src_width;
+            let src_height = *src_height;
+
             let rel_x = pos.x - min_x_aligned;
             let rel_y = pos.y - min_y_aligned;
 
             let tile_x = (rel_x / TILE_SIZE).round() as u32;
             let tile_y = (height_tiles as f32 - 1.0 - (rel_y / TILE_SIZE).round()) as u32;
 
-                    let target_x = tile_x * TILE_PIXELS;
-                    let target_y = tile_y * TILE_PIXELS;
-                    let mut data: Vec<&[u8]> = vec![];
-
-                    let mut base_texture: &Image = &Default::default();
-
-                    // Use a thread-safe approach to access images
-                    // In a full implementation, this would require a more sophisticated
-                    // thread-safe access pattern to Assets<Image>
-                    if let Some(_base_texture) = images.get(texture) {
-                        if let Some(_data) = &_base_texture.data {
-                            data.push(_data);
-                            base_texture = _base_texture;
-                        }
-                    }
-
             blit_texture_with_alpha(
-                        data,              // tile
+                source,
-                        &mut texture_data, // terrain
+                &mut texture_data,
-                        base_texture.size().x as u32,
+                src_width,
-                        base_texture.size().y as u32,
+                src_height,
                 width_px,
                 height_px,
-                        target_x,
+                tile_x * TILE_PIXELS,
-                        target_y,
+                tile_y * TILE_PIXELS,
             );
         }
-            }
-        }
 
-        // Create the quilted texture
         let quilted_texture = Image::new_fill(
             render_resource::Extent3d {
                 width: width_px,
@@ -192,29 +298,27 @@ pub fn build_quilted_terrain_sprites(
             RenderAssetUsages::RENDER_WORLD,
         );
 
-        // In a real implementation, we would need thread-safe access to images
-        // For now, we'll collect the textures and add them after parallel processing
         let center_x = min_x_aligned + (max_x_aligned - min_x_aligned) / 2.0;
         let center_y = min_y_aligned + (max_y_aligned - min_y_aligned) / 2.0;
 
-        // Store texture and position data for later spawning
+        // Return buffer to pool for the next bake.
-        texture_handles_mutex
+        buffer_pool.lock().unwrap().insert(key, texture_data);
+
+        texture_results
             .lock()
             .unwrap()
-            .insert(z_index, (quilted_texture, center_x, center_y));
+            .push((key, quilted_texture, center_x, center_y));
     });
 
-    // Process collected textures and spawn entities
+    // --- Drain and store results back on the main thread ---
-    let collected_dimensions = dimensions_mutex.into_inner().unwrap();
-    let collected_textures = texture_handles_mutex.into_inner().unwrap();
 
-    // Update quilt_cache dimensions
+    quilt_cache.pixel_buffers = buffer_pool.into_inner().unwrap();
-    for (z_index, dimensions) in collected_dimensions {
+
-        quilt_cache.dimensions.insert(z_index, dimensions);
+    for (key, dimensions) in dimensions_results.into_inner().unwrap() {
+        quilt_cache.dimensions.insert(key, dimensions);
     }
 
-    // Add images and spawn entities with the collected data
+    for (key, quilted_texture, center_x, center_y) in texture_results.into_inner().unwrap() {
-    for (z_index, (quilted_texture, center_x, center_y)) in collected_textures {
         let texture_handle = images.add(quilted_texture);
 
         commands.command_scope(|mut cmd| {
@@ -230,19 +334,24 @@ pub fn build_quilted_terrain_sprites(
                 )
                 .with_scale(Vec3::splat(PIXEL_RATIO)),
                 Visibility::Hidden,
-                TerrainSprite { z_index },
+                TerrainSprite { key },
             ));
         });
     }
 
-    quilt_cache.dirty_indices.clear();
+    quilt_cache.dirty_keys.clear();
     cwss.state = TerrainSpriteState::RenderReady;
-    println!("Terrain sprites baked in: {:.2?}", now.elapsed());
+    println!(
+        "Terrain sprites baked in: {:.2?} ({} chunks×z, {} full)",
+        now.elapsed(),
+        tiles_by_chunk_z.len(),
+        if full_bake { "yes" } else { "no" },
+    );
 }
 
-// Helper function to blit a texture onto another texture
+/// Blits `source` onto `target` at (`offset_x`, `offset_y`) with per-pixel alpha compositing.
 fn blit_texture_with_alpha(
-    sources: Vec<&[u8]>,
+    source: &[u8],
     target: &mut [u8],
     source_width: u32,
     source_height: u32,
@@ -251,7 +360,6 @@ fn blit_texture_with_alpha(
     offset_x: u32,
     offset_y: u32,
 ) {
-    for (_, source_data) in sources.iter().rev().enumerate() {
     for y in 0..source_height {
         if y + offset_y >= target_height {
             continue;
@@ -261,41 +369,33 @@ fn blit_texture_with_alpha(
                 continue;
             }
 
-                let source_pixel_idx = ((y * source_width) + x) as usize * 4;
+            let src_idx = ((y * source_width) + x) as usize * 4;
-                let target_pixel_idx =
+            let dst_idx = (((y + offset_y) * target_width) + (x + offset_x)) as usize * 4;
-                    (((y + offset_y) * target_width) + (x + offset_x)) as usize * 4;
 
-                let src_a = source_data[source_pixel_idx + 3];
+            let src_a = source[src_idx + 3];
 
             if src_a == 0 {
                 continue;
             }
 
-                let src_r = source_data[source_pixel_idx];
-                let src_g = source_data[source_pixel_idx + 1];
-                let src_b = source_data[source_pixel_idx + 2];
-
             if src_a == 255 {
-                    target[target_pixel_idx] = src_r;
+                target[dst_idx] = source[src_idx];
-                    target[target_pixel_idx + 1] = src_g;
+                target[dst_idx + 1] = source[src_idx + 1];
-                    target[target_pixel_idx + 2] = src_b;
+                target[dst_idx + 2] = source[src_idx + 2];
-                    target[target_pixel_idx + 3] = 255;
+                target[dst_idx + 3] = 255;
             } else {
-                    let dst_r = target[target_pixel_idx];
+                let alpha = src_a as f32 / 255.0;
-                    let dst_g = target[target_pixel_idx + 1];
+                let inv_alpha = 1.0 - alpha;
-                    let dst_b = target[target_pixel_idx + 2];
 
-                    let alpha_factor = src_a as f32 / 255.0;
+                target[dst_idx] =
-                    let inv_alpha = 1.0 - alpha_factor;
+                    (source[src_idx] as f32 * alpha + target[dst_idx] as f32 * inv_alpha) as u8;
-
+                target[dst_idx + 1] = (source[src_idx + 1] as f32 * alpha
-                    target[target_pixel_idx] =
+                    + target[dst_idx + 1] as f32 * inv_alpha)
-                        (src_r as f32 * alpha_factor + dst_r as f32 * inv_alpha) as u8;
+                    as u8;
-                    target[target_pixel_idx + 1] =
+                target[dst_idx + 2] = (source[src_idx + 2] as f32 * alpha
-                        (src_g as f32 * alpha_factor + dst_g as f32 * inv_alpha) as u8;
+                    + target[dst_idx + 2] as f32 * inv_alpha)
-                    target[target_pixel_idx + 2] =
+                    as u8;
-                        (src_b as f32 * alpha_factor + dst_b as f32 * inv_alpha) as u8;
+                target[dst_idx + 3] = 255;
-                    target[target_pixel_idx + 3] = 255;
-                }
             }
         }
     }

src/world/tiles/visibility.rs

@@ -186,7 +186,7 @@ pub fn update_tile_visibility(
     let now = Instant::now();
 
     for (terrain_sprite, mut visibility) in query.iter_mut() {
-        *visibility = if terrain_sprite.z_index == ((z_index.0 + Z_BELOW) as usize) {
+        *visibility = if terrain_sprite.key.z_index == ((z_index.0 + Z_BELOW) as usize) {
             Visibility::Visible
         } else {
             Visibility::Hidden