data/Assets/Tutorial/pages/Full body tracking.asset

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  m_overrideMarkdownText: '# Full Body Tracking


    NorthStar supports full-body
    tracking using the [Meta Movement SDK](https://developers.meta.com/horizon/documentation/unity/move-overview/).
    The SDK provides a solid foundation, and we have implemented additional logic
    to meet the project''s needs.


    ![](./Images/FullBodyTracking/Fig1.png)


    ##
    Meta Movement SDK Setup


    To set up body tracking, follow these steps:

    -
    Right-click the player rig GameObject.

    - Select the body tracking setup
    option.


    ![](./Images/FullBodyTracking/Fig0.png)


    This process configures
    the RetargetingLayer component and the FullBodyDeformationConstraint, which work
    effectively out of the box.


    ## Calibration


    **Avatar Scaling**


    After
    the player calibrates their height in the menu, we scale the player avatar to
    match. We adjust the player rig based on the initial height versus the player''s
    height, accounting for any height offset.


    #### Relevant Files

    - [PlayerCalibration.cs](../Assets/NorthStar/Scripts/Player/PlayerCalibration.cs)


    **Seated
    vs Standing**


    NorthStar supports both seated and standing play. We added
    an offset to the player rig to ensure the player appears standing in the game,
    even when seated. This offset is calculated from the difference between the player''s
    calibrated standing and seated height, adjustable in the menu.


    The full-body
    tracking system does not support manual offsets, causing the player rig to crouch
    regardless of skeleton adjustments. To address this, we use only upper body tracking
    and manage leg placement ourselves.


    **Custom Leg Solution**


    ![](./Images/FullBodyTracking/Fig2.png)


    Initially,
    we used the built-in full-body tracking leg solution from the Movement SDK, which
    worked for standing play but not for seated play. We developed an alternative
    leg-IK solution using Unity''s rigging package, providing similar functionality
    for foot placement, stepping, and crouching.


    #### Relevant Files

    -
    [BodyPositions.cs](../Assets/NorthStar/Scripts/Player/BodyPositions.cs)


    ##
    Postprocessors


    **Physics Hands Retargeting**


    Using physically simulated
    hands required a RetargetingProcessor to retarget the hands with IK. The CustomRetargetingProcessorCorrectHand
    is a modified version of the original from Meta, supporting hand rotation and
    position overrides.


    #### Relevant Files

    - [CustomRetargetingProcessorCorrectHand.cs](../Assets/NorthStar/Scripts/Player/CustomRetargetingProcessorCorrectHand.cs)


    **Hands,
    Elbow, and Twist Bone Correction**


    After retargeting the hand and arm bones,
    the elbow and twist bones may misalign. We introduced a processor to correct
    their orientation, keeping the elbow locked to one axis relative to the shoulder
    and distributing wrist rotation along the twist and wrist bones. This processor
    also aligns the tracked finger bones with the player''s tracked hands.


    ####
    Relevant Files

    - [SyntheticHandRetargetingProcessor.cs](../Assets/NorthStar/Scripts/Player/SyntheticHandRetargetingProcessor.cs)


    ##
    Tracking Failure


    Full-body tracking can fail in several cases, such as
    failing to initialize, especially during Oculus Link testing. When tracking failure
    is detected, we switch off the full-body rig and revert to standard floating
    ghost hands. We also attempt to restart body tracking when the headset wakes
    from sleep or is put back on.


    A persistent bug remains where the player''s
    body is squished into the floor without any SDK-reported tracking failure. The
    cause is currently unknown.


    ## Future Improvements


    The full-body
    tracking implementation has issues that need improvement, such as slight alignment
    problems with the avatar''s head and feet floating off the ground in seated mode.

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