# Hand¶

Hand Class Reference

The Hand class reports the physical characteristics of a detected hand. More...

## Public Member Functions

bool Equals (Hand other)
Compare Hand object equality. More...

Finger Finger (int id)
The Finger object with the specified ID attached to this hand. More...

Hand ()
Constructs a Hand object. More...

Hand (long frameID, int id, float confidence, float grabStrength, float grabAngle, float pinchStrength, float pinchDistance, float palmWidth, bool isLeft, float timeVisible, Arm arm, List< Finger > fingers, Vector palmPosition, Vector stabilizedPalmPosition, Vector palmVelocity, Vector palmNormal, LeapQuaternion palmOrientation, Vector direction, Vector wristPosition)
Constructs a hand. More...

override string ToString ()
A string containing a brief, human readable description of the Hand object. More...

## Public Attributes

Arm Arm
The arm to which this hand is attached. More...

float Confidence
How confident we are with a given hand pose. More...

Vector Direction
The direction from the palm position toward the fingers. More...

List< FingerFingers
The list of Finger objects detected in this frame that are attached to this hand, given in order from thumb to pinky. More...

float GrabAngle
The angle between the fingers and the hand of a grab hand pose. More...

float GrabStrength
The strength of a grab hand pose. More...

int Id
A unique ID assigned to this Hand object, whose value remains the same across consecutive frames while the tracked hand remains visible. More...

bool IsLeft
Identifies whether this Hand is a left hand. More...

Vector PalmNormal
The normal vector to the palm. More...

Vector PalmPosition
The center position of the palm in millimeters from the Leap Motion Controller origin. More...

Vector PalmVelocity
The rate of change of the palm position in millimeters/second. More...

float PalmWidth
The estimated width of the palm when the hand is in a flat position. More...

float PinchDistance
The distance between the thumb and index finger of a pinch hand pose. More...

float PinchStrength
The holding strength of a pinch hand pose. More...

LeapQuaternion Rotation
The rotation of the hand as a quaternion. More...

Vector StabilizedPalmPosition
The stabilized palm position of this Hand. More...

float TimeVisible
The duration of time this Hand has been visible to the Leap Motion Controller. More...

Vector WristPosition
The position of the wrist of this hand. More...

## Properties

LeapTransform Basis [get]
The transform of the hand. More...

bool IsRight [get]
Identifies whether this Hand is a right hand. More...

## Detailed Description

The Hand class reports the physical characteristics of a detected hand.

Hand tracking data includes a palm position and velocity; vectors for the palm normal and direction to the fingers; properties of a sphere fit to the hand; and lists of the attached fingers.

Get Hand objects from a Frame object:

Frame frame = controller.Frame (); // controller is a Controller object
if(frame.Hands.Count > 0){
List<Hand> hands = frame.Hands;
Hand firstHand = hands [0];
}

Note that Hand objects can be invalid, which means that they do not contain valid tracking data and do not correspond to a physical entity. Invalid Hand objects can be the result of asking for a Hand object using an ID from an earlier frame when no Hand objects with that ID exist in the current frame. A Hand object created from the Hand constructor is also invalid. Test for validity with the Hand::isValid() function.

Since
1.0

## Constructor & Destructor Documentation

 Hand ( )

Constructs a Hand object.

An uninitialized hand is considered invalid. Get valid Hand objects from a Frame object.

if(frame.Hands.Count > 0){
Hand hand = frame.Hands[0];
}
Since
1.0
 Hand ( long frameID, int id, float confidence, float grabStrength, float grabAngle, float pinchStrength, float pinchDistance, float palmWidth, bool isLeft, float timeVisible, Arm arm, List< Finger > fingers, Vector palmPosition, Vector stabilizedPalmPosition, Vector palmVelocity, Vector palmNormal, LeapQuaternion palmOrientation, Vector direction, Vector wristPosition )

Constructs a hand.

Generally, you should not create your own Hand objects. Such objects will not have valid tracking data. Get valid Hand objects from a frame received from the service.

Parameters
 frameID Id of the frame this hand belongs to id The hand identifier confidence The estimate of data fitness grabStrength The grab posture rating of the hand grabAngle The average angle of the fingers to the hand pinchStrength The pinch posture rating of the hand pinchDistance The distance in millimeters between the thumb and index finger tips when pinching palmWidth the width of the hand isLeft True, if this is a left hand timeVisible The amount of time this hand has been visible arm The arm object for this hand fingers The list of fingers for this hand palmPosition The position of the palm stabilizedPalmPosition The time-filtered position of the palm palmVelocity The velocity vector of the hand Vector palmNormal The normal vector to the palm direction The direction of the hand wristPosition The position of the wrist
Since
3.0

## Member Function Documentation

 bool Equals ( Hand other )

Compare Hand object equality.

Boolean handIsEqual = thisHand.Equals(thatHand);

Two Hand objects are equal if and only if both Hand objects represent the exact same physical hand in the same frame and both Hand objects are valid.

Since
1.0
 Finger Finger ( int id )

The Finger object with the specified ID attached to this hand.

Use the Hand::finger() function to retrieve a Finger object attached to this hand using an ID value obtained from a previous frame. This function always returns a Finger object, but if no finger with the specified ID is present, an invalid Finger object is returned.

Finger fingerOnHandByID = hand.Finger (fingerID);

Note that ID values persist across frames, but only until tracking of a particular object is lost. If tracking of a finger is lost and subsequently regained, the new Finger object representing that finger may have a different ID than that representing the finger in an earlier frame.

Parameters
 id The ID value of a Finger object from a previous frame.
Returns
The Finger object with the matching ID if one exists for this hand in this frame; otherwise, an invalid Finger object is returned.
Since
1.0
 override string ToString ( )

A string containing a brief, human readable description of the Hand object.

Returns
A description of the Hand as a string.
Since
1.0

## Member Data Documentation

The arm to which this hand is attached.

If the arm is not completely in view, Arm attributes are estimated based on the attributes of entities that are in view combined with typical human anatomy.

Arm arm = hand.Arm;
Returns
The Arm object for this hand.
Since
2.0.3
 float Confidence

How confident we are with a given hand pose.

The confidence level ranges between 0.0 and 1.0 inclusive.

float confidence = hand.Confidence;
Since
2.0
 Vector Direction

The direction from the palm position toward the fingers.

The direction is expressed as a unit vector pointing in the same direction as the directed line from the palm position to the fingers.

You can use the palm direction vector to compute the pitch and yaw angles of the palm with respect to the horizontal plane:

float pitch = hand.Direction.Pitch;
float yaw = hand.Direction.Yaw;
float roll = hand.PalmNormal.Roll;
Returns
The Vector pointing from the palm position toward the fingers.
Since
1.0
 List Fingers

The list of Finger objects detected in this frame that are attached to this hand, given in order from thumb to pinky.

The list cannot be empty.

Use PointableList::extended() to remove non-extended fingers from the list.

// hand is a Hand object
List<Finger> fingers = hand.Fingers;
Returns
The List<Finger> containing all Finger objects attached to this hand.
Since
1.0
 float GrabAngle

The angle between the fingers and the hand of a grab hand pose.

The angle is computed by looking at the angle between the direction of the 4 fingers and the direction of the hand. Thumb is not considered when computing the angle. The angle is 0 radian for an open hand, and reaches pi radians when the pose is a tight fist.

Returns
The angle of a grab hand pose between 0 and pi radians (0 and 180 degrees).
Since
3.0
 float GrabStrength

The strength of a grab hand pose.

The strength is zero for an open hand, and blends to 1.0 when a grabbing hand pose is recognized.

float strength = hand.GrabStrength;
Returns
A float value in the [0..1] range representing the holding strength of the pose.
Since
2.0
 int Id

A unique ID assigned to this Hand object, whose value remains the same across consecutive frames while the tracked hand remains visible.

If tracking is lost (for example, when a hand is occluded by another hand or when it is withdrawn from or reaches the edge of the Leap Motion Controller field of view), the Leap Motion software may assign a new ID when it detects the hand in a future frame.

Use the ID value with the Frame::hand() function to find this Hand object in future frames:

Hand knownHand = frame.Hand (handID);
Returns
The ID of this hand.
Since
1.0
 bool IsLeft

Identifies whether this Hand is a left hand.

string handName = hand.IsLeft ? "Left hand" : "Right hand";
Returns
True if the hand is identified as a left hand.
Since
2.0
 Vector PalmNormal

The normal vector to the palm.

If your hand is flat, this vector will point downward, or "out" of the front surface of your palm.

The direction is expressed as a unit vector pointing in the same direction as the palm normal (that is, a vector orthogonal to the palm).

You can use the palm normal vector to compute the roll angle of the palm with respect to the horizontal plane:

float pitch = hand.Direction.Pitch;
float yaw = hand.Direction.Yaw;
float roll = hand.PalmNormal.Roll;
Returns
The Vector normal to the plane formed by the palm.
Since
1.0
 Vector PalmPosition

The center position of the palm in millimeters from the Leap Motion Controller origin.

Vector handCenter = hand.PalmPosition;
Returns
The Vector representing the coordinates of the palm position.
Since
1.0
 Vector PalmVelocity

The rate of change of the palm position in millimeters/second.

Vector handSpeed = hand.PalmVelocity;
Returns
The Vector representing the coordinates of the palm velocity.
Since
1.0
 float PalmWidth

The estimated width of the palm when the hand is in a flat position.

float handWidth = hand.PalmWidth;
Returns
The width of the palm in millimeters
Since
2.0
 float PinchDistance

The distance between the thumb and index finger of a pinch hand pose.

The distance is computed by looking at the shortest distance between the last 2 phalanges of the thumb and those of the index finger. This pinch measurement only takes thumb and index finger into account.

Returns
The distance between the thumb and index finger of a pinch hand pose in millimeters.
Since
3.0
 float PinchStrength

The holding strength of a pinch hand pose.

The strength is zero for an open hand, and blends to 1.0 when a pinching hand pose is recognized. Pinching can be done between the thumb and any other finger of the same hand.

float pinch = hand.PinchStrength;
Returns
A float value in the [0..1] range representing the holding strength of the pinch pose.
Since
2.0
 LeapQuaternion Rotation

The rotation of the hand as a quaternion.

Since
3.1
 Vector StabilizedPalmPosition

The stabilized palm position of this Hand.

Smoothing and stabilization is performed in order to make this value more suitable for interaction with 2D content. The stabilized position lags behind the palm position by a variable amount, depending primarily on the speed of movement.

Vector filteredHandPosition = hand.StabilizedPalmPosition;
Returns
A modified palm position of this Hand object with some additional smoothing and stabilization applied.
Since
1.0
 float TimeVisible

The duration of time this Hand has been visible to the Leap Motion Controller.

Returns
The duration (in seconds) that this Hand has been tracked.
Since
1.0
 Vector WristPosition

The position of the wrist of this hand.

Returns
A vector containing the coordinates of the wrist position in millimeters.
Since
2.0.3

## Property Documentation

 LeapTransform Basis
get

The transform of the hand.

Note, in version prior to 3.1, the Basis was a Matrix object.

Since
3.1
 bool IsRight
get

Identifies whether this Hand is a right hand.

if (hand.IsRight) {
// .. Do right handed stuff
}
Returns
True if the hand is identified as a right hand.
Since
2.0