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Unigine::LeapMotion::Bone Struct

Header:#include <LeapMotionInterface.h>
LeapMotion plugin must be loaded.

This structure represents a bone of a finger and has the following set of properties:

type Bone type. One of the Bone::TYPE_* values.
length Length of the bone, in meters.
witdh Width of the bone, in meters.
is_valid Indicates whether the bone contains valid tracking data (1).
prev_joint Coordinates of the end of the bone, closest to the wrist (proximal).
next_joint Coordinates of the end of the bone, closest to the finger tip (distal).
center Coordinates of the center of the bone.
direction Normalized direction of the bone from wrist to tip.

Orthonormal basis vectors for the bone as a Matrix.

Basis vectors specify the orientation of the 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. Increases in the upward direction.
  • Z - Aligned with the longitudinal axis of the bone. Increases toward the base of the finger.

The bases 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.

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 bases.
All coordinates are relative to the origin of the Leap Motion coordinate system.
The Bone structure is declared as follows:
Source code (C++)
struct Bone
	int type;
	float length;
	float width;
	int is_valid;
	Unigine::Math::vec3 prev_joint;
	Unigine::Math::vec3 next_joint;
	Unigine::Math::vec3 center;
	Unigine::Math::vec3 direction;
	Unigine::Math::mat4 basis;
Last update: 2018-04-26