Hand tracking in Unreal

The hand tracking system uses a person’s palms and fingers as input. Data on position and rotation of every finger, the entire palm, and hand gestures is available.

Hand Pose

Hand pose lets you track and use the hands and fingers of your users as input. You can access tracking data both in Blueprints and C++. You can find more technical details in Unreal's Windows.Perception.People.HandPose API. The Unreal API sends the data as a coordinate system, with ticks synchronized with the Unreal Engine.

Understanding the bone hierarchy

The EWMRHandKeypoint enum describes the Hand’s bone hierarchy. You can find each hand keypoint listed in your Blueprints:

Hand Keypoint BP

The full C++ enum is listed below:

enum class EWMRHandKeypoint : uint8

You can find the numerical values for each enum case in the Windows.Perception.People.HandJointKind table. The entire hand pose layout with matching enum cases is shown in the image below:

Hand Skeleton

Supporting Hand Tracking

You can use hand tracking in Blueprints by adding Supports Hand Tracking from Hand Tracking > Windows Mixed Reality:

Hand Tracking BP

This function returns true if hand tracking is supported on the device and false if hand tracking isn't available.

Supports Hand Tracking BP


Include WindowsMixedRealityHandTrackingFunctionLibrary.h.

static bool UWindowsMixedRealityHandTrackingFunctionLibrary::SupportsHandTracking()

Getting Hand Tracking

You can use GetHandJointTransform to return spatial data from the hand. The data updates every frame, but if you're inside a frame the returned values are cached. It's not recommended to have heavy logic in this function for performance reasons.

Get Hand Joint Transform


static bool UWindowsMixedRealityHandTrackingFunctionLibrary::GetHandJointTransform(EControllerHand Hand, EWMRHandKeypoint Keypoint, FTransform& OutTransform, float& OutRadius)

Here's a breakdown of GetHandJointTransform's function parameters:

  • Hand – can be the users left or right hand.
  • Keypoint – the bone of the hand.
  • Transform – coordinates and orientation of bone’s base. You can request the base of the next bone to get the transform data for the end of a bone. A special Tip bone gives end of distal.
  • Radius — radius of the base of the bone.
  • Return Value — true if the bone is tracked this frame, false if the bone isn't tracked.

Hand poses are exposed to Animation using the Live Link plugin.

If the Windows Mixed Reality and Live Link plugins are enabled:

  1. Select Window > Live Link to open the Live Link editor window.
  2. Select Source and enable Windows Mixed Reality Hand Tracking Source

Live Link Source

After you enable the source and open an animation asset, expand the Animation section in the Preview Scene tab too see additional options.

Live Link Animation

The hand animation hierarchy is the same as in EWMRHandKeypoint. Animation can be retargeted using WindowsMixedRealityHandTrackingLiveLinkRemapAsset:

Live Link Animation 2

It can also be subclassed in the editor:

Live Link Remap

Accessing Hand Mesh Data

Hand Mesh

Before you can access hand mesh data, you'll need to:

  • Select your ARSessionConfig asset, expand the AR Settings -> World Mapping settings, and check Generate Mesh Data from Tracked Geometry.

Below are the default mesh parameters:

  1. Use Mesh Data for Occlusion
  2. Generate Collision for Mesh Data
  3. Generate Nav Mesh for Mesh Data
  4. Render Mesh Data in Wireframe – debug parameter that shows generated mesh

These parameter values are used as the spatial mapping mesh and hand mesh defaults. You can change them at any time in Blueprints or code for any mesh.

C++ API Reference

Use EEARObjectClassification to find hand mesh values in all trackable objects.

enum class EARObjectClassification : uint8
    // Other types 

The following delegates are called when the system detects any trackable object, including a hand mesh.

class FARSupportInterface 
    // Other params 

Make sure your delegate handlers follow the function signature below:

void UARHandMeshComponent::OnTrackableAdded(UARTrackedGeometry* Added)

You can access mesh data through the UARTrackedGeometry::GetUnderlyingMesh:

UMRMeshComponent* UARTrackedGeometry::GetUnderlyingMesh()

Blueprint API Reference

To work with Hand Meshes in Blueprints:

  1. Add an ARTrackableNotify Component to a Blueprint actor

ARTrackable Notify

  1. Go to the Details panel and expand the Events section.

ARTrackable Notify 2

  1. Overwrite On Add/Update/Remove Tracked Geometry with the following nodes in your Event Graph:

On ARTrackable Notify

Hand Rays

You can use a hand ray as a pointing device in both C++ and Blueprints, which exposes the Windows.UI.Input.Spatial.SpatialPointerInteractionSourcePose API.


Since all function results change every frame, they're all made callable. For more information about pure and impure or callable functions, see the Blueprint user guid on functions.

To use Hand Rays in Blueprints, search for any of the actions under Windows Mixed Reality HMD:

Hand Rays BP

To access them in C++, include WindowsMixedRealityFunctionLibrary.h to the top of your calling code file.


You also have access to input cases under EHMDInputControllerButtons, which can be used in Blueprints:

Input Controller Buttons

For access in C++, use the EHMDInputControllerButtons enum class:

enum class EHMDInputControllerButtons : uint8

Below is a breakdown of the two applicable enum cases:

  • Select - User triggered Select event.
    • Triggered in HoloLens 2 by air-tap, gaze, and commit, or by saying “Select” with voice input enabled.
  • Grasp - User triggered Grasp event.
    • Triggered in HoloLens 2 by closing the user’s fingers on a hologram.

You can access the tracking status of your hand mesh in C++ through the EHMDTrackingStatus enum shown below:

enum class EHMDTrackingStatus : uint8

Below is a breakdown of the two applicable enum cases:

  • NotTracked –- the hand isn’t visible
  • Tracked –- the hand is fully tracked


The PointerPoseInfo struct can give you information on the following hand data:

  • Origin – origin of the hand
  • Direction – direction of the hand
  • Up – up vector of the hand
  • Orientation – orientation quaternion
  • Tracking Status – current tracking status

You can access the PointerPoseInfo struct through Blueprints, as shown below:

Pointer Pose Info BP

Or with C++:

struct FPointerPoseInfo
	FVector Origin;
	FVector Direction;
	FVector Up;
	FQuat Orientation;
	EHMDTrackingStatus TrackingStatus;


All of the functions listed below can be called on every frame, which allows continuous monitoring.

  1. Get Pointer Pose Info returns complete information about the hand ray direction in the current frame.


Get Pointer Pose Info


static FPointerPoseInfo UWindowsMixedRealityFunctionLibrary::GetPointerPoseInfo(EControllerHand hand);
  1. Is Grasped returns true if the hand is grasped in the current frame.


Is Grasped BP


static bool UWindowsMixedRealityFunctionLibrary::IsGrasped(EControllerHand hand);
  1. Is Select Pressed returns true if the user triggered Select in the current frame.


Is Select Pressed BP


static bool UWindowsMixedRealityFunctionLibrary::IsSelectPressed(EControllerHand hand);
  1. Is Button Clicked returns true if the event or button is triggered in the current frame.


Is Button Clicked BP


static bool UWindowsMixedRealityFunctionLibrary::IsButtonClicked(EControllerHand hand, EHMDInputControllerButtons button);
  1. Get Controller Tracking Status returns the tracking status in the current frame.


Get Controller Tracking Status BP


static EHMDTrackingStatus UWindowsMixedRealityFunctionLibrary::GetControllerTrackingStatus(EControllerHand hand);


The HoloLens 2 tracks spatial gestures, which means you can capture those gestures as input. You can find more details about gestures are the HoloLens 2 Basic Usage document.

You can find the Blueprint function in under Windows Mixed Reality Spatial Input, and the C++ function by adding WindowsMixedRealitySpatialInputFunctionLibrary.h in your calling code file.

Capture Gestures



Gesture Type


enum class ESpatialInputAxisGestureType : uint8
	None = 0,
	Manipulation = 1,
	Navigation = 2,
	NavigationRails = 3


You can enable and disable gesture capture with the CaptureGestures function. When an enabled gesture fires input events, the function returns true if gesture capture succeeded, and false if there's an error.


Capture Gestures BP


static bool UWindowsMixedRealitySpatialInputFunctionLibrary::CaptureGestures(
	bool Tap = false, 
	bool Hold = false, 
	ESpatialInputAxisGestureType AxisGesture = ESpatialInputAxisGestureType::None, 
	bool NavigationAxisX = true, 
	bool NavigationAxisY = true, 
	bool NavigationAxisZ = true);

The following are key events, which you can find in Blueprints and C++: Key Events

Key Events 2

const FKey FSpatialInputKeys::TapGesture(TapGestureName);
const FKey FSpatialInputKeys::DoubleTapGesture(DoubleTapGestureName);
const FKey FSpatialInputKeys::HoldGesture(HoldGestureName);

const FKey FSpatialInputKeys::LeftTapGesture(LeftTapGestureName);
const FKey FSpatialInputKeys::LeftDoubleTapGesture(LeftDoubleTapGestureName);
const FKey FSpatialInputKeys::LeftHoldGesture(LeftHoldGestureName);

const FKey FSpatialInputKeys::RightTapGesture(RightTapGestureName);
const FKey FSpatialInputKeys::RightDoubleTapGesture(RightDoubleTapGestureName);
const FKey FSpatialInputKeys::RightHoldGesture(RightHoldGestureName);

const FKey FSpatialInputKeys::LeftManipulationGesture(LeftManipulationGestureName);
const FKey FSpatialInputKeys::LeftManipulationXGesture(LeftManipulationXGestureName);
const FKey FSpatialInputKeys::LeftManipulationYGesture(LeftManipulationYGestureName);
const FKey FSpatialInputKeys::LeftManipulationZGesture(LeftManipulationZGestureName);

const FKey FSpatialInputKeys::LeftNavigationGesture(LeftNavigationGestureName);
const FKey FSpatialInputKeys::LeftNavigationXGesture(LeftNavigationXGestureName);
const FKey FSpatialInputKeys::LeftNavigationYGesture(LeftNavigationYGestureName);
const FKey FSpatialInputKeys::LeftNavigationZGesture(LeftNavigationZGestureName);

const FKey FSpatialInputKeys::RightManipulationGesture(RightManipulationGestureName);
const FKey FSpatialInputKeys::RightManipulationXGesture(RightManipulationXGestureName);
const FKey FSpatialInputKeys::RightManipulationYGesture(RightManipulationYGestureName);
const FKey FSpatialInputKeys::RightManipulationZGesture(RightManipulationZGestureName);

const FKey FSpatialInputKeys::RightNavigationGesture(RightNavigationGestureName);
const FKey FSpatialInputKeys::RightNavigationXGesture(RightNavigationXGestureName);
const FKey FSpatialInputKeys::RightNavigationYGesture(RightNavigationYGestureName);
const FKey FSpatialInputKeys::RightNavigationZGesture(RightNavigationZGestureName);

Next Development Checkpoint

If you're following the Unreal development journey we've laid out, you're in the midst of exploring the MRTK core building blocks. From here, you can continue to the next building block:

Or jump to Mixed Reality platform capabilities and APIs:

You can always go back to the Unreal development checkpoints at any time.