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Unigine::Plugins::LeapMotion::Hand Struct

Notice
LeapMotion plugin must be loaded.

Hands are the main entity tracked by the Leap Motion controller. The controller maintains an inner model of the human hand and validates the data from its sensors against this model. This allows the controller to track finger positions even when a finger is not completely visible.

Notice
It is possible for movement or changes in position to be lost when a finger is behind or directly in front of the hand (from the point of view of the controller).

The Leap Motion software matches the internal model against the existing data. In some cases, the software can make an incorrect match – for example, identifying a right hand as a left hand.

This structure represents a physical hand detected by the Leap and provides access to its attributes describing the hand position, orientation, and movement. All coordinates are relative to the origin of the Leap Motion coordinate system.

The Hand structure is declared as follows:

Source code (C++)
struct Hand
{
	int id;
	int type;
	int is_valid;
	float palm_width;
	Unigine::Math::vec3 palm_position;
	Unigine::Math::vec3 palm_stabilized_position;
	Unigine::Math::vec3 wrist_position;
	Unigine::Math::vec3 palm_velocity;
	Unigine::Math::vec3 palm_normal;
	Unigine::Math::vec3 direction;
	Unigine::Math::mat4 basis;

	Arm arm;
	Unigine::Map<int, Finger> fingers;
};

struct Hand

Fields

  • int id - Identifier of the hand.
  • int type - Type of the hand:
    • 0 - left hand
    • 1 - right hand
  • float palm_width - Width of the palm when the hand is in a flat position, in meters.
  • Math::vec3 palm_position - Coordinates of the position of the palm.
    Notice
    All coordinates are relative to the origin of the Leap Motion coordinate system.
  • Math::vec3 palm_stabilized_position - Coordinates of the modified palm position with some additional smoothing and stabilization applied. 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.
    Notice
    All coordinates are relative to the origin of the Leap Motion coordinate system.
  • Math::vec3 wrist_position - Coordinates of the position of the wrist.
    Notice
    All coordinates are relative to the origin of the Leap Motion coordinate system.
  • Math::vec3 palm_velocity - Rate of change of the palm position, in m/s.
  • Math::vec3 palm_normal - Coordinates of the normal vector to the palm. If a hand is flat, this vector will point downward, or "out" of the front surface of your palm.
    Notice
    All coordinates are relative to the origin of the Leap Motion coordinate system.
  • Math::vec3 direction - Normalized direction from the palm position toward the fingers.
    Notice
    All coordinates are relative to the origin of the Leap Motion coordinate system.
  • Math::mat4 basis - Orthonormal basis vectors for this Bone as a Matrix.

    Basis vectors specify the orientation of a bone:

    • X - Perpendicular to the longitudinal axis of the bone; exits the sides of the finger.
    • Y (or up vector) - Perpendicular to the longitudinal axis of the bone; exits the top and bottom of the finger. More positive in the upward direction.
    • Z - Aligned with the longitudinal axis of the bone. More positive toward the base of the finger.

    The basis provided for the right hand use the right-hand rule; those for the left hand use the left-hand rule. Thus, the positive direction of the x-basis is to the right for the right hand and to the left for the left hand. You can change from right-hand to left-hand rule by multiplying the z basis vector by -1.

    You can use the basis vectors for such purposes as measuring complex finger poses and skeletal animation.

    Notice
    Converting the basis vectors directly into a quaternion representation is not mathematically valid. If you use quaternions, create them from the derived rotation matrix not directly from the basis.
  • int is_valid - 1 if the hand contains valid tracking data; otherwise, 0.
  • LeapMotion::Arm arm - Arm of the hand.
  • Unigine::Map<int, Finger> finger - List of all fingers of the hand.
Last update: 2023-06-23
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