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Unreal SDK release notes

Release notes for the AR 51 Unreal SDK. The core plugin connects Unreal Engine to an AR 51 capture server (Mocap Unleashed) and drives characters from live markerless capture; optional platform plugins add VR-headset input on top. Newest release first.

The SDK ships as one package per Unreal Engine version. Each core release lists the engine versions it targets.

Version boundaries

Release tags weren't recorded for every build, so for versions before 2.3.1.73 the changes are grouped to the nearest version. The changes come from the actual code history; which exact build first shipped a given change is approximate.

Core plugin​

2.3.2.4​

2026-03 · UE 5.6 – 5.8 · since 2.3.1.74

Extends support to the latest Unreal Engine versions, with mapping and tracking refinements.

Improved​

  • Character mapping now works without requiring the Blueprint _C class suffix by default, while remaining backward compatible with existing setups.
  • Multi-bone forearm/wrist twist for more natural arm deformation.
  • OpenXR reports hands correctly when the anchor is applied to the camera.

Compatibility​

  • Adds support for Unreal Engine 5.6, 5.7 and 5.8 (building on the 5.3–5.5 line).
  • Existing bone mappings and characters from the 2.3.1 line continue to work.

2.3.1.74​

2025-09 to 2025-10 · UE 5.3 – 5.5 · since 2.3.1.73

Focused on lower latency, tighter control over which people are tracked, and steadier VR hand tracking.

New​

  • Active-person camera space. Choose whether the "active person" is picked in the camera's local space or in world space.
  • Skeleton count limit. Cap how many skeletons are consumed at once (unlimited by default).
  • Capture timestamp access. Read the timestamp of the most recent skeleton frame from Blueprints.

Improved​

  • Lower end-to-end latency through linear prediction on incoming skeleton data.
  • Steadier VR hands. Fingers are only applied when wrist confidence is valid; on bad headset data the last good hand pose is held instead of jittering.
  • Tracking-loss compensation is now off by default for more predictable behaviour.

Compatibility​

  • Targets Unreal Engine 5.3, 5.4 and 5.5, with broad backward-compatibility work down to UE 4.27 / 5.3.

2.3.1.73​

2025-05 · UE 5.3 – 5.4 · since 2.3.1.51

A tracking-quality release that rolls up the spring-2025 IK and twist work.

Improved​

  • Better tracking-loss compensation. Putting on or removing a headset no longer triggers a false tracking-lost correction.
  • VR fingers from the server are respected — hands are not re-solved when the headset already provides them.
  • Calf and hand correction scaling to fix anatomical mismatches (foot-rotation artefacts and hand auto-scaling).
  • Single- and multi-joint forearm twist solving.

Fixed​

  • Corrected anchor transform maths so anchored content is placed correctly.
  • Graceful fallback when a character asset is missing, plus guards against unstable frame timing.

2.3.1.51​

2025-05 · UE 5.3 – 5.4 · since 2.3.1.46

Adds flexible control over how detected people are matched to characters.

New​

  • Auto character-assignment modes — Default, Cycle and Random — for deciding which character a newly detected person drives.
  • Assign a character by Person ID or Entity ID (by name or index) from Blueprints.
  • Main-camera override with Blueprint get/set.
  • Anchor lifecycle events (created / destroyed) and hand-stream start/stop events.

Improved​

  • Confidence-aware solving. Low-confidence joints are excluded from auto-scaling and rotation, and per-joint confidence is exposed on each person.
  • Stability hardening to avoid touching components after they have been cleaned up.

Compatibility​

  • The singleton accessor was renamed; the previous accessor still works but is deprecated and reports guidance to move to the new one.

2.3.1.46​

2025-02 · UE 5.3 · since 2.3.1.27

Improved​

  • Unified platform-plugin model. Each platform now registers a single plugin, simplifying which platform plugins you enable for OpenXR, RenderStream and others.
  • Quest hand tracking now roots its transform on the camera anchor for correct placement.

2.3.1.27​

2025-01 · UE 5.3 · since 2.3.1.19

New​

  • Expanded Blueprint API. Many skeleton-consumer and per-person operations are now callable from Blueprints, including resetting a character or the active character, plus an active-person-changed event.

Improved​

  • Both hands are now handled symmetrically before being broadcast.
  • The camera anchor is the default scene component, and each person can report the capture device it came from.

2.3.1.19​

2024-11 to 2024-12 · UE 5.3 + Android · since 2.3.1.10

New​

  • Network overrides for advanced setups. Override the local IP and the server address to skip auto-discovery, and exclude specific ports when opening connections.
  • Object detection improvements. Markers can carry a map rather than a single point, and objects can be attached to markers.
  • Stable public API surface. A clean integration interface is exposed without internal networking headers, giving integrators a stable surface to build against.

Improved​

  • Android support and multi-target packaging.
  • Switching a person's character at runtime, per-device ID overrides, and a skeleton parent-constraint component.

Fixed​

  • Crash fixes around shutdown with two editor instances and around person creation.

2.3.1.10​

2024-10 · UE 4.27 / 5.1 / 5.3 / 5.4 · initial packaged release

The first packaged AR 51 Unreal SDK.

New​

  • Self-contained package that bundles the libraries it needs so the plugin runs on other machines.
  • Skeleton-to-character bone remapping, an inverse world-anchor constraint, and an adjustable hand-smoothing factor.
  • Unreal Engine 5.4 support alongside the existing 4.27 / 5.1 / 5.3 targets.

Platform plugins​

Optional plugins that add VR-headset input on top of the core plugin. Enable only the one(s) for your target hardware.

Streams AR 51 capture into Unreal's Live Link framework, so AR 51 subjects appear alongside your other Live Link sources.

  • 2.3.2.4 (2026 · UE 5.6 – 5.8) — Compatibility updates for Unreal Engine 5.6 and 5.8.
  • 2.3.1.48 / 2.3.1.47 (2025 · UE 5.3 – 5.5) — Improved clavicle handling; the Live Link source factory is now public so integrators can reference it directly. (2.3.1.48 is a version bump over the same 2.3.1.47 codebase.)
  • 2.3.1.10 (2024 · UE 4.27 – 5.4) — Initial packaged Live Link support: multiple person subjects, virtual-subject management, a show-model option, and play-in-editor guards so AR 51 code only runs when appropriate. Ships with source.

OpenXR plugin​

Adds OpenXR headset and hand-tracking input, and is the recommended path for Meta Quest headsets.

  • 2.3.1.47 (2025 · UE up to 5.6) — OpenXR now reports hands when the anchor is applied to the camera; hand-adapter fix.
  • 2.3.1.46 (2025 · UE 5.3) — Device-platform specifiers added; a new OpenXR sample map; fixed a case where OpenXR on Quest never switched to "tracked," so finger input never arrived. OpenXR now registers on all platforms regardless of the selected platform.
  • 2.3.1.10 (2024 · UE 4.27 – 5.3) — Initial OpenXR support: 3D hand visualisation, palm-width gating to reject spurious tiny hands, and guardian checks only while the headset is worn.

Pico plugin​

VR input for Pico headsets.

  • 2.3.1.51 (2025 · UE 5.3) — First Pico release. Calibrates and renders hands on UE 5.3; hand material is configurable from Blueprint, hands are red by default to distinguish them from Pico's own hand rendering, hands are hidden by default, and there is an option to hide hands below a confidence threshold.

Quest plugin (legacy)​

Legacy — use the OpenXR plugin for Quest

The standalone Quest plugin is no longer actively developed. It receives only occasional changes to keep it compiling on newer engines, and has had no new features since 2024. For Meta Quest headsets, use the OpenXR plugin instead — it is the maintained path and fixes Quest finger tracking.

  • 2.3.1.13 / 2.3.1.12 (2024 · UE 5.3 · Android) — Legacy Quest headset input (hand tracking via the Oculus/Quest integration). Superseded by the OpenXR plugin.
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