horizon-airdef/docs/java-packs.md

Java performance packs (no longer developed)

Before the Rust rewrite, Horizon was a lab for Minecraft Java client performance: pinned Fabric performance packs, distant terrain, an original frame and tick recorder, and client and server starter downloads. This track is no longer developed. No release downloads are published; build the packs and starters locally with python3 tools/build_release.py (see Build and run). This page keeps its documentation.

Java packs: Mac starter (out of scope)

Build horizon-mac-starter-0.21.0.zip with python3 tools/build_release.py (it lands in dist/), extract it and open Mac-Start.command. It verifies and installs official universal Prism Launcher in ~/Applications if needed, then opens the balanced pack import. Sign into Microsoft inside Prism yourself. This project needs no credentials.

Use native Java 25 ARM64, maximum heap 6144 MiB, minimum 512 MiB on a 16 GB M2 Pro Mac. Prism can download Java automatically. Start at 1280×800 or 1920×1200; full Retina resolution is a larger GPU workload. START-HERE.txt has details. The same .mrpack files import into Prism on Windows and Linux.

If Prism is already installed, follow the Mac import and first comparison guide.

Core and balanced also pass macOS title/demo-world rendering probes on the hosted ARM64 software renderer, including readback, saves and clean exits. Physical M2 GPU performance and macOS 27 remain to be tested.

Profile	Full-detail chunks	Distant LOD radius	Suggested maximum heap
baseline	12	none	6144 MiB
core-performance	12	none	6144 MiB
m2-balanced	12	128	6144 MiB
adaptive (experiment)	12	128	6144 MiB
worker-pacing (experiment)	12	128	6144 MiB
adaptive-pacing (experiment)	12	128	6144 MiB
queue-wait (experimental)	12	128	6144 MiB
adaptive-queue (experimental)	12	128	6144 MiB
dispatch-retry (experimental)	12	128	6144 MiB
tick-dedup (experimental)	12	128	6144 MiB
culling-empty (experimental)	12	128	6144 MiB
quad-reuse (experimental)	12	128	6144 MiB
terrain-position (experimental)	12	128	6144 MiB
culling-rays (experimental)	12	128	6144 MiB
foreground-first (combined experiment)	12	128	6144 MiB
foreground-vulkan (combined experiment)	12	128	6144 MiB
low-memory	8	none	3072 MiB
far-distance	12	256	8192 MiB, with sufficient physical RAM
cinematic	12	128	6144 MiB
vulkan	12	128	6144 MiB

Balanced combines Sodium, Lithium, FerriteCore, ImmediatelyFast, EntityCulling, and Distant Horizons. Cinematic adds Iris and Complementary Reimagined, initially disabled. Vulkan independently experiments with the game's own backend and fallback, without Iris.

Distant LOD is simplified terrain. Nearby blocks retain full detail. Initial generation costs CPU/disk/memory and needs warm-up. DH adjusts clouds, chunk fade and transparency to blend its renderer; assess appearance as well as speed. Shaders cost GPU time and have Mac-specific limits. Universal CPU/GPU support and exact vanilla equivalence remain validation goals. Simulation distance stays 12 in every profile; normal 20 TPS rules are retained.

For the first comparison at the same view distance, use baseline versus core-performance: both select 12 full-detail chunks and no distant LOD or shaders. The latter adds only the pinned core performance mods and leaves every original controller disabled. Then test balanced separately for its additional distant terrain. Matching captured settings does not prove pixel-identical rendering. Core comparison protocol and selected observations include three repeated matched-view software-rendered pairs with 14–21% higher FPS in this workload; M2 performance remains unmeasured.

Heap budget experiment: three pairs with 3 GiB versus 1.5 GiB maximum heap show variable RAM savings and GC/frame-time tradeoffs; playable defaults remain unchanged.

Matched graphics API comparison: Vulkan adds about 1.5% average FPS but about 12% CPU in three Linux software-rendered pairs; backend defaults remain unchanged and physical Mac performance is unmeasured.

The optional queue-wait pack yields during pending distant-terrain debounce retries; adaptive-queue combines it with the existing controllers. Queue experiment and measurement limits.

Version 0.16 adds a separate terrain position arithmetic experiment for the sampled full-data lookup. It retains the pinned library’s unusual negative-coordinate rounding and invalid-level errors. Balanced keeps it off; whole-game and Mac performance still require measurement.

Version 0.15 adds an isolated culling ray scratch experiment that reuses two numeric vectors within each culling instance while retaining upstream arithmetic and decisions. Balanced keeps it off; hardware gains remain unmeasured.

Version 0.14 adds an isolated empty culling whitelist experiment that avoids allocating iterators while there are no dynamic handlers. Live registration and nonempty callbacks retain upstream behavior. Balanced keeps it off; whole-game gains still need hardware comparisons. DH profiles also request a scoped interruptible blending-read wait to let background workers leave a pending metadata read during shutdown.

Version 0.13 adds an isolated tick membership experiment that reuses compact storage for DH's private per-tick membership checks. The combined foreground profiles include it too; balanced keeps it off. The applied holder test verifies action semantics and removes repeated entry allocations; whole-game FPS and RAM gains still need hardware measurements.

Version 0.12 captures effective distant-terrain quality, radius, worker budgets, Iris state and field of view. Start/end snapshots flag changed visual settings; measurement details explain their limits.

Version 0.11 adds combined foreground-first OpenGL/Vulkan profiles with a 120 FPS adaptive goal, plus explicit collector experiments and GC measurement guidance. See combined controls, Vulkan on your Mac and collector comparisons. The frame goal is not a rendering cap.

Version 0.10 adds an isolated rejected-dispatch retry experiment. It bounds retry passes when a DH worker rejects queued work, preserving original requeue handling and allowing other executors to progress. Balanced keeps it off.

Version 0.9 also makes the queue's idle wait wakeable for incoming work, preserving its debounce rules and bounded cache-maintenance cadence. It remains part of the optional queue profiles, with separate wake-latency measurements.

Version 0.8 fixes a fresh-instance graphics preset that could override the selected render distance. It also records actual GC/header settings and supports an optional compact object headers experiment for Java 25; packs do not enable that JVM flag automatically.

Measure on your hardware

The optional adaptive terrain experiment throttles distant terrain background work when frames slow down or heap pressure rises, keeping the balanced profile's view distances and simulation settings. It remains opt-in until real hardware demonstrates a benefit.

The additional precise worker pacing experiment makes short terrain tasks respect their duty-cycle budget and avoids boxed worker timestamps. It changes generation speed and CPU use, so it stays separate from balanced.

Press F8 during gameplay to start a 120-second recording, or again to stop early. Rebind in Controls if needed. This also works with restricted chat accounts. Alternatively: /horizon bench <label> 120, /horizon stop, /horizon status.

Use separate identical world copies and the same camera route, resolution, render/simulation distance, heap, VSync and FPS limit. Warm up, then alternate at least three baseline/optimized runs. Test fresh chunk exploration separately. For everyday play cap FPS or enable VSync to reduce power usage.

The instance's horizon-benchmarks/ folder receives JSON/CSV frame and integrated-server tick timings: average FPS, slowest-1%-average FPS, p95/p99 durations, stalls, JVM heap/GC, sampled process RSS when available, GPU/backend/driver and render settings. Frames include presentation/limiting waits and exclude menus/pauses/unfocused time. Tick meanRate is execution capacity, not TPS; observed tick counts are separate. Version 0.20 captures sampled tick-manager state, including restored freeze/step/sprint/rate changes; this does not measure completed world work. Resident process memory is sampled on a shared background thread only during recordings; it includes native resident pages, while heap measures JVM objects. Neither is a complete measurement of unified GPU memory. Memory measurement details.

python3 tools/compare_benchmarks.py baseline-frames.json optimized-frames.json --strict

Open Compare-Benchmarks.html from the starter ZIP or the source file in your browser to compare without Python. Select each JSON and optionally its matching CSV. It exports summary JSON, flags settings and duration differences, and charts frames by recorded active time or ticks by sample number. It is self-contained and makes no network requests.

Version 0.18 adds an isolated terrain quad reuse experiment. It reuses a temporary quad discarded by successful premerge when the existing pool would otherwise allocate. Generated geometry and thread ownership checks pass; allocation results are not whole-game RAM or FPS evidence. It remains off in combined profiles.

Version 0.17 also records loaded mod versions and the Java vendor, VM and runtime build in client and server reports. Both comparison tools flag software changes as explicit experiment variables; older reports remain usable with an unknown software warning. The viewer can expand the complete loaded mod list. Live software identity check records the metadata and file-count validation; its short capture is not a performance comparison.

The comparison flags captured setting differences, but cannot verify route, world, shader state or cache warm-up. See validation evidence. Software-renderer test FPS is not evidence of a Mac/GPU speedup.

For CPU/allocation investigation, capture and stream a private JFR summary. It distinguishes directly observed allocation counters from sampled hot methods; profiling runs remain separate from normal timing comparisons.

Build and run

Requires Python 3.10+ and JDK 25. No Gradle, Rust or native compilation is required for playable packs.

python3 tools/build_mod.py
python3 tools/build_release.py

Gitignored dist/ contains twenty packs, our original instrumentation JAR, client/server starter ZIPs and SHA256SUMS. mods.lock.json pins mod versions, exact dependency closure, SHA-1/SHA-512 and source/license; fabric.lock.json pins loader/library SHA-256. Packs use the Modrinth format. They embed only original project code; third-party mods, game and assets download from their publishers.

The server starter uses Lithium/FerriteCore and /horizonserver bench <label> <seconds>. Server instructions cover setup and a baseline. Files are prepared before you accept Minecraft's EULA locally. A 50-active-player workload remains to be measured.

Local smoke testing uses the game's built-in limited demo; normal play uses Prism's licensed account authentication:

python3 tools/build_pack.py --profile m2-balanced --instance .local/runtime/m2-balanced
vscreen run python3 tools/runtime.py demo --instance .local/runtime/m2-balanced

The standalone demo launcher applies the pinned official manifest's conditional JVM flags, including macOS -XstartOnFirstThread and the Windows heap-dump-path option. Prism applies its own official manifest. Server JVM policy is separate; this launcher correction is not a measured graphics performance improvement.