Create Optimized Trains

v1.3.2

Focus

• Fixes the remaining Copycats+ bit lag, a critical world-load freeze, and last-carriage movement stutter
• All fixes are follow-ups discovered while stress-testing v1.3.1 on maps with 40+ trains and Copycats+ bit-heavy contraptions

Bug Fixes

Copycats+ Periodic Lag (Bit Blocks with BlockEntity)

• Contraptions containing Copycats+ "bits" (sub-block sized pieces with a BlockEntity, unlike plain slabs/panels) caused periodic lag spikes every few seconds
• Root cause: ContraptionWorld does not override getBlockEntity(), so it fell back to WrappedLevel.getBlockEntity(), which queried the real world using the contraption's local coordinates (e.g. 5,1,3) — forcing the server to load/query the chunk at real-world (0,0) on every call
• Fix: ContraptionWorldBlockEntityMixin intercepts getBlockEntity() on Level (filtered to ContraptionWorld instances) and always serves the BlockEntity from contraption.getBlocks(), with a lazy per-instance cache — never touching the real world with local coordinates

World Freeze on Startup (Memory Pressure)

• On some world loads, especially after the server had been running a while, the game would hang completely at the loading screen (no crash, just a full freeze)
• Root cause: heap memory pressure genuinely reaching 90%+ during startup, mainly from Distant Horizons' distant world generation competing with ~40 Create contraptions being assembled simultaneously — triggering long stop-the-world GC pauses (minutes-long in the worst case)
• Fix: DistantHorizonsThrottle temporarily reduces DH's distant world generation and worker thread count for the first startupThrottleTicks (default 200 ticks / 10s) after the server starts, giving vanilla terrain and contraption assembly priority. DH's original settings are restored automatically afterwards. Uses DH's public API via reflection — no hard dependency

Last-Carriage Movement Stutter

• Long trains (10+ carriages) without a player on board showed irregular movement — the stutter would noticeably improve once the rearmost carriage's entity finally loaded
• Root cause: ChunkLoadManager's per-tick chunk load rate limit applied to every needed chunk indiscriminately, including the exact chunk each carriage physically occupies. On unoccupied trains, that chunk competed with lookahead/trailing chunks for the same 6-per-tick budget, so the last carriage in line could take several ticks just to get its own chunk loaded — delaying its entity creation
• Fix: chunk requests are now split into critical (the exact chunk under each carriage — always loaded immediately, no rate limit, regardless of occupancy) and soft (LOD comfort radius, directional lookahead, trailing buffer — still rate-limited). No carriage, including the rearmost one, waits behind empty pre-load chunks anymore

Chunks Not Unloading When a Train Stops

• Chunks along a train's previous travel direction could remain force-loaded indefinitely after the train stopped, accumulating over a session and degrading performance over time
• Root cause: the anti-thrash "recently loaded" deque only advances when new chunks are loaded; once a train stops, nothing loads, so old lookahead chunks stayed protected from unloading forever
• Fix: the anti-thrash deque is cleared as soon as a train's speed drops below the movement threshold, letting unneeded chunks unload immediately

Improvements

Chunk Loading Tuning

• Adaptive lookahead margin increased from ~2s to ~5s of travel time, to reliably cover cold-terrain chunk generation (which can take 2-3s) — default cap raised from 10 to 20 chunks
• Per-tick chunk load budget reduced to 6 chunks with a 5ms time budget per train, preventing a single train's chunk update from blocking the whole server tick
• Non-occupied trains now have their chunk updates staggered across ticks (5 trains per batch, every 3 ticks) instead of all being processed every tick, reducing aggregate setChunkForced calls per tick on maps with many trains

Diagnostics

• Added granular performance logging ([COT/Perf], [COT] updateTrainChunks detalhe) to break down slow ticks by train and by phase (chunk calculation, unload, load)
• Added [COT/ContraptionWorldBE] activity counter to confirm the Copycats+ BlockEntity fix is intercepting calls as expected

Configuration

New config section in create_optimized_trains-common.toml:

• [distant_horizons] — startupThrottleEnabled (default true), startupThrottleTicks (default 200, range 20-1200)