🎭Autodesk MotionBuilder Plugin

Preview, record, analyze, and bake YanusLIVE PRO facial data in MotionBuilder with YanusLink.

YanusLink for Autodesk MotionBuilder

YanusLink is a MotionBuilder device plug-in that receives facial animation data from YanusLIVE PRO.

It separates live preview from final curve generation. Preserve source data, review or recover recordings, then safely bake to a new animation layer.

YanusLIVE PRO → Live UDP streaming → MotionBuilder preview
→ Raw .ylfs spool → Analysis → Animation-layer bake

Supported versions and features

Autodesk MotionBuilder 2025 and 2026 are supported.

YanusLink supports:

• Live Link Face v6 UDP reception and real-time facial preview

• Multiple cameras and subjects, ARKit blendshapes, and head and eye rotation

• Raw .ylfs spool recording, offline analysis, and repeat baking

• New animation-layer baking with rollback after failure or cancellation

• Automatic baking, interrupted-recording recovery, and diagnostic bundles

Data channels

YanusLink receives up to 61 channels.

Channel group	Count	Description
ARKit BlendShapes	52	Standard ARKit facial channels
Head Rotation	3	Yaw, Pitch, Roll
Left Eye Rotation	3	Yaw, Pitch, Roll
Right Eye Rotation	3	Yaw, Pitch, Roll
Total	61	Full Live Link Face v6 channel set

Blendshape values usually range from 0.0–1.0. Rotation values use radians.

The production binding profile uses 48 facial channels. It excludes these optional right-eye look channels:

eyeLookDownRight
eyeLookInRight
eyeLookOutRight
eyeLookUpRight

Excluded channels are reported as optional exclusions, not missing bindings.

Installation

Save the current MotionBuilder scene. Close MotionBuilder and mobupy.exe. Then run the YanusLink installer.

The plug-in installs as a per-user MotionBuilder module.

%USERPROFILE%\Documents\MB\Modules\MotionTechnologies.YanusLink\

The installed structure is:

MotionTechnologies.YanusLink\
├── MotionTechnologies.YanusLink.mod
├── 2025\plugins\LiveLinkFaceDevice.dll
└── 2026\plugins\LiveLinkFaceDevice.dll

The module descriptor loads the plug-in matching the running MotionBuilder version.

Confirm the installation

1. Start MotionBuilder.

2. Open Asset Browser or Devices.

3. Find the YanusLink device.

4. Add LinkYanus to the current scene.

The plug-in loaded successfully when the YanusLink icon appears.

Configure the live connection

Add the device

1. Open Asset Browser.

2. Navigate to Devices.

3. Drag LinkYanus into the scene.

4. Open the device properties.

The device has Live and Offline Bake tabs. Use Live for networking, subjects, preview, and binding. Use Offline Bake for recording analysis, baking, recovery, and diagnostics.

Stream from YanusLIVE PRO

Enable Live Link output in YanusLIVE PRO. Use a unique device ID and subject name for each camera.

Camera_1
Camera_2
Camera_3
Camera_4

YanusLIVE PRO sends the device ID, subject name, source frame number, sub-frame, source frame rate, and facial values.

Configure the Live tab

Enter the YanusLIVE PRO UDP port in Port. Select the incoming subject in Subject.

Create one YanusLink device for each independently controlled character.

LinkYanus 1 → Camera_1 → Character A
LinkYanus 2 → Camera_2 → Character B
LinkYanus 3 → Camera_3 → Character C

Clamp limits facial values to 0.0–1.0. Scale adjusts overall facial strength. A typical starting value is 100. Rotation Scale independently adjusts head and eye rotation.

Go online

1. Enable the device.

2. Set the device to Online.

3. Enable Live evaluation.

4. Confirm that the packet count increases.

5. Confirm the displayed subject matches the source.

6. Confirm stable receive FPS.

Before recording, check packet count, receive FPS, subject, last-packet time, dropped-frame statistics, and binding status.

Handle tracking loss

When packet reception stops, use one of these stale-data policies:

Mode	Behavior
Hold	Keeps the last facial pose.
Reset	Immediately returns every channel to neutral.
Decay	Smoothly fades the current pose to neutral.

Use Decay for production. Start with Stale Timeout: 300 ms and Decay Duration: 200 ms.

Character binding

Before Auto Bind, load the target character and verify its animatable facial properties and ARKit-compatible shapes. Select the target model in YanusLink.

Auto Bind inspects the target facial properties, finds supported channels, configures a Relation Constraint, and connects device outputs to character shapes.

YanusLink Device → Relation Constraint → Character Shape Properties → Live Preview

Test blinks, jaw movement, lips, and head rotation. Review connected, missing, and excluded channels in the binding summary.

Recording

YanusLink uses MotionBuilder Transport recording controls. The plug-in has no separate production record button.

Start MotionBuilder Record → Write source frames to a .ylfs spool → Stop Record → Finalize spool

Prepare to record

Before recording, confirm:

1. YanusLink is Online and live preview works.

2. The correct subject, target character, and binding are selected.

3. The correct Take and start time are selected.

4. Sufficient disk space is available.

The Take, subject, target model, local start time, and recording ID remain fixed during the session.

Record and locate files

1. Press Record in MotionBuilder Transport.

2. Start playback or capture.

3. Perform facial motion in YanusLIVE PRO.

4. Stop recording from Transport.

Source frames are written to a .ylfs spool file.

%USERPROFILE%\Documents\MB\2025\Recordings\
%USERPROFILE%\Documents\MB\2026\Recordings\

Example filename:

20260722_142530_Take001_Camera_1_g0001.ylfs

The spool preserves source frames and frame numbers. It detects dropped source frames and supports repeat baking with different settings.

Reconstruct the timeline

YanusLIVE PRO sends source inference frame numbers, not UDP packet counters. For example, 100, 101, 102, 108, 109 indicates missing or skipped source frames.

YanusLink anchors the first received frame to the local recording start time. It then reconstructs the timeline from source time.

$$\text{Source Time} = (\text{frame number} + \text{sub-frame}) \times \frac{\text{frame rate denominator}}{\text{frame rate numerator}}$$

This preserves the true recording duration when source frames are missing.

Offline analysis and baking

Select and analyze a recording

After recording, open Offline Bake and select the latest recording or browse to a .ylfs file. Confirm the active Take, target character, binding, and spool before analysis.

Analyze validates spool integrity, frame count and duration, source frame rate, frame gaps, target model, binding, active Take, existing key ranges, and bake settings.

State	Meaning
Ready	The recording can be baked.
Warning	Baking can continue, but review is recommended.
Blocked	A required condition is not met.
Analysis Stale	The scene or settings changed after analysis.
Target Missing	The target character model is unavailable.
Binding Missing	Required facial properties are disconnected.
Existing-Key Conflict	Existing animation prevents this operation.

Analysis identifies the spool, options, target, Take, binding, and existing curve state. Analyze again after changing the target, Take, binding, bake mode, or existing curves.

Bake modes

Mode	Use
Full	Creates a key for every valid source sample.
Fixed Rate	Resamples data at the selected FPS.
Threshold	Creates keys only after changes exceed the threshold.
Error Bound	Reduces curves within the selected maximum error.

Use Error Bound for general production. It preserves facial quality while reducing redundant keys.

Bake to a new animation layer

The release workflow always creates a new MotionBuilder animation layer. This separates new facial animation from existing scene animation and protects existing data.

1. Select the spool, target, bake mode, and backend.

2. Click Analyze and review warnings.

3. Resolve blocking issues.

4. Click Bake.

5. Review the new animation layer.

Read spool → Reconstruct source timeline → Plan and reduce curves
→ New-layer transaction → Write FCurves → Validate → Commit or roll back

If baking fails or is cancelled, YanusLink removes partial curves and the new layer. Existing scene animation and the source .ylfs file remain intact.

Snapshot Bake preserves the visible animation before applying new facial curves. Use it when existing animation outside the selected range must remain unchanged.

Automatic baking and recovery

Automatically bake after recording

Enable Auto Bake After Record in Advanced. After spool finalization, YanusLink analyzes the recording and bakes it to a new layer with Error Bound mode.

Automatic baking stops when a target or binding is missing, keys conflict, a spool is incomplete, disk space is low, another device is baking, the Take changes, or analysis becomes stale. Review the warning in Offline Bake and continue manually.

Recover interrupted recordings

An unexpected exit can leave an incomplete spool with a .part extension. Do not use it through the normal bake path.

1. Open Recovery in Offline Bake.

2. Click Refresh.

3. Select a recovery candidate.

4. Click Recover Selected Recording.

5. Select the recovered spool.

6. Run Analyze and review every warning.

7. Start a manual bake.

Diagnostics

For troubleshooting, open Diagnostics in Offline Bake and click Create Diagnostic Bundle. Use Open Diagnostics Folder when needed.

%USERPROFILE%\Documents\MB\2025\Diagnostics\
%USERPROFILE%\Documents\MB\2026\Diagnostics\

The diagnostic bundle can include the plug-in version, DLL path, port, subject, target, online status, last packet, recording and bake state, disk status, and recovery candidates.

Recommended workflow

Install YanusLink → Add LinkYanus → Configure port and subject → Select target
→ Auto Bind → Enable Online and Live → Verify preview
→ MotionBuilder Record → Stop Record → Offline Bake
→ Select spool → Analyze → Bake to new layer → Review and save

Start with these recommended settings:

Stale Mode: Decay
Stale Timeout: 300 ms
Decay Duration: 200 ms
Facial Scale: 100
Bake Mode: Error Bound
Bake Destination: New Animation Layer
Legacy Packets: Off

Use a unique subject for each camera. Do not change the subject or target during recording. Keep .ylfs files until final animation approval.

Troubleshooting

Device does not appear

Close MotionBuilder completely. Verify the installation folder and the DLL for the target version. Restart MotionBuilder and open Asset Browser. Reinstall YanusLink if needed.

No packets are received

Check YanusLIVE PRO streaming, the UDP port, selected subject, Windows Firewall, and network interface. Confirm that packet count increases, last-packet time updates, and receive FPS is above zero.

Data arrives but the character does not move

Verify the target model and Auto Bind result. Enable the Relation Constraint and Live evaluation. Test with a known channel such as jawOpen.

Analyze is blocked

Check for a missing target or binding, incorrect Take, incomplete spool, existing-key conflict, or stale analysis. Resolve the issue, then run Analyze again.

Bake fails

Review the result message and confirm rollback completed. Confirm MotionBuilder is not recording. Verify that the spool is finalized, then analyze again. Create a diagnostic bundle if the issue persists.

Animation has too many keys

Use Fixed Rate, Threshold, or Error Bound. For production, adjust the maximum error in Error Bound. Use Full only when every sample is required.

Facial motion freezes after tracking loss

The stale policy may be Hold. Select Decay for a smooth return to neutral, or Reset for an immediate return.