Bone¶

Properties:

Methods:

class Leap::Bone

The Bone class represents a tracked bone.

All fingers contain 4 bones that make up the anatomy of the finger. Get valid Bone objects from a Finger object.

Bones are ordered from base to tip, indexed from 0 to 3. Additionally, the bone’s Type enum may be used to index a specific bone anatomically.

List<Finger> fingers = hand.Fingers;
foreach(Finger finger in fingers){
Bone bone;
foreach (Bone.BoneType boneType in (Bone.BoneType[]) Enum.GetValues(typeof(Bone.BoneType)))
{
bone = finger.Bone(boneType);
// ... Use bone
}
}


The thumb does not have a base metacarpal bone and therefore contains a valid, zero length bone at that location.

Since
2.0

Public Type

BoneType enum

Enumerates the names of the bones.

Members of this enumeration are returned by Bone::type() to identify a Bone object.

Since
2.0

Values:

• TYPE_INVALID = = -1 -
• TYPE_METACARPAL = = 0 -
• TYPE_PROXIMAL = = 1 -
• TYPE_INTERMEDIATE = = 2 -
• TYPE_DISTAL = = 3 -
Public Functions

Bone()

Constructs a default Bone object.

Since
2.0

Bone(Vector prevJoint, Vector nextJoint, Vector center, Vector direction, float length, float width, Bone.BoneType type, LeapQuaternion rotation)

Constructs a new Bone object.

Since
3.0
Parameters
• prevJoint -

The proximal end of the bone (closest to the body)

• nextJoint -

The distal end of the bone (furthest from the body)

• center -

The midpoint of the bone

• direction -

The unit direction vector pointing from prevJoint to nextJoint.

• length -

The estimated length of the bone.

• width -

The estimated average width of the bone.

• type -

The type of finger bone.

• basis -

The matrix representing the orientation of the bone.

bool Equals(Bone other)

Compare Bone object equality.

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

Since
2.0

override string ToString()

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

String description = bone.ToString();


Return
A description of the Bone object as a string.
Since
2.0

Public Members

Vector Center

The midpoint of the bone.

Vector middle = bone.Center;


Return
The midpoint in the center of the bone.
Since
2.0

Vector Direction

The normalized direction of the bone from base to tip.

Vector direction = bone.Direction;


Return
The normalized direction of the bone from base to tip.
Since
2.0

float Length

The estimated length of the bone in millimeters.

float length = bone.Length;


Return
The length of the bone in millimeters.
Since
2.0

Vector NextJoint

The end of the bone, closest to the finger tip.

In anatomical terms, this is the distal end of the bone.

Vector boneEnd = bone.NextJoint;


Return
The Vector containing the coordinates of the next joint position.
Since
2.0

Vector PrevJoint

The base of the bone, closest to the wrist.

In anatomical terms, this is the proximal end of the bone.

Vector boneStart = bone.PrevJoint;


Return
The Vector containing the coordinates of the previous joint position.
Since
2.0

LeapQuaternion Rotation

The orientation of this Bone as a Quaternion.

Return
The Quaternion.
Since
2.0

Bone.BoneType Type

The name of this bone.

Bone.BoneType type = bone.Type;


Return
The anatomical type of this bone as a member of the Bone::Type enumeration.
Since
2.0

float Width

The average width of the flesh around the bone in millimeters.

float width = bone.Width;


Return
The width of the flesh around the bone in millimeters.
Since
2.0

Property

LeapTransform Basis

The orthonormal basis vectors for this Bone as a Matrix.

The orientation of this Bone as a Quaternion.

Basis vectors specify the orientation of a bone.

xBasis Perpendicular to the longitudinal axis of the bone; exits the sides of the finger.

yBasis 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.

zBasis Aligned with the longitudinal axis of the bone. More positive 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.

Note that 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.

LeapTransform basis = bone.Basis;
Vector xBasis = basis.xBasis;
Vector yBasis = basis.yBasis;
Vector zBasis = basis.zBasis;


Return
The basis of the bone as a matrix.
Return
The Quaternion.
Since
2.0

Extension Functions¶

public static Bone CopyFrom(this Bone bone, Bone source)¶

Copies the data from a source bone into this bone. After the operation is complete, the bone will be identical to the source bone.

Parameter: source The source bone that is copied into this bone.

public static Bone Transform(this Bone bone, LeapTransform transform)¶

Does an in-place, rigid transformation of this Bone.

Parameter: transform A LeapTransform containing the desired translation, rotation, and scale to be applied to this Bone.

public static Bone TransformedCopy(this Bone bone, LeapTransform transform)¶

Returns a new bone that is a copy of this bone, with an additional rigid transformation applied to it.

Parameter: transform The transformation to be applied to the copied bone.