512 chunks/frame in debug, 1024 in release. In release, recolor runs
~2x faster so 1024 still costs ~1ms but clears the dirty queue twice
as fast, closing the p99 gap during rapid z-scrolling.
Negative world z (below ground) was excluded by the clamp, making the
visible window asymmetrically large. Dirty count now proportional to
actual scroll distance. Frame time dropped from ~13ms to ~8.3ms avg.
Boundary: mark all z-levels where z_diff changed, not just 4 boundary
indices. For multi-step scrolls, every z-level between
min(old,new)-8 and max(old,new) inclusive needs recoloring.
Also fixes last_z_change_dirty_count to use actual new_keys.len().
Recolor: update tileset_index alongside color so sky tile switch at
t>=0.98 actually renders the sky texture, not sky-coloured grass.
Cleanup: removed solid_bits (was unused after recolor fix).
Three optimizations for z-scroll performance:
Option 1 — Fast in-place recolor (no HashMap lookups):
- TilemapChunkStates stores solid_bits + underground_bits per chunk
- recolor_chunk_for_depth iterates flat Vec<Option<TileData>> — pure cache-friendly sequential reads
- tile_fade_color computes color from tileset_idx + z_diff without any HashMap access
- vs repopulate_chunk_tiles: 32K Vec reads vs 32K HashMap lookups per frame
Option 2 — Targeted boundary dirty (from 9×chunks to 2×chunks):
- on_camera_z_changed now only marks the 4 boundary z-levels:
old_entered, old_exited, new_entered, new_exited
- Registry.z_change_keys tracks z-changed keys separately from occlusion dirty_keys
- populate_tilemap_chunk_data uses fast recolor for z_change_keys,
full repopulate for dirty_keys (occlusion — rare)
Option 3 — Separate budgets:
- z_change_keys processed with MAX_POPULATE_PER_FRAME budget (fast recolor)
- dirty_keys processed with MAX_POPULATE_PER_FRAME budget (full repopulate)
- Both pipelines tracked separately in benchmark
Also:
- populate_chunk_tiles now returns underground_bits for state storage
- compute_solid_bits helper extracts solid tiles from TileData Vec
- spawn_tilemap_chunks computes and stores both bitmasks on spawn
- despawn_tilemap_chunks clears all state for despawned chunks
on_camera_z_changed: only dirty z-levels whose z_diff changed
(both old and new camera positions, within 0..=8 window).
Previously dirtied all 20k entities on every z-change.
populate_tilemap_chunk_data: process up to MAX_POPULATE_PER_FRAME
(512) keys per frame, sorted by z-distance from current camera.
Spreads z-scroll cost across multiple frames instead of one spike.
TilemapBenchmark: added z-change spike instrumentation
(last_z_change_dirty_ms, last_z_change_dirty_count,
last_z_change_populate_ms, z_change_history_ms).
F9 report now shows z-scroll metrics.
PreviousZIndex resource tracks prior camera z for targeted dirty calc.
- tile_for_depth: alpha always 1.0, lerp RGB from white toward sky RGB
instead of fading tile out via alpha. Tiles stay opaque.
- Expose LAYER_ALPHA as pub const so it can be tuned at runtime
- LAYER_ALPHA changed from 41/255 to 50/255 for steeper visible fade
- Invisible tiles: explicit solid sky colour, not tile_for_depth(0, 999)
Replace df_fade_color (multiplicative tint that preserves texture hue)
with tile_for_depth which cross-fades between real tile and sky tile:
- z_diff <= 0: real tile at full opacity (no fade)
- z_diff in (0, threshold): real tile fades out via alpha
- z_diff past threshold: sky tile (index 0) fades in
- invisible tiles: solid sky colour
Also fix tile_id_to_tileset_index to include sky (id=0) as index 0,
so sky tiles render correctly as the fade target.
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