Joint labels

Kinect joint labels

The Kinect v2 system tracks a skeleton using the following 21 joints:

_images/kinect_joint_labels.png

Qualisys and Kualisys joint labels

The standard setup for the Qualisys system uses 44 joint labels. Joints with transparency are located in the back of the subject:

_images/qualisys_joint_labels.png

Due to the inconsistency in naming of the joints (e.g. “BackL” and “LArm”), the joints are automatically renamed in Krajjat to follow a more consistent approach, based on the Kinect labelling. The toolbox names these Kualisys joint labels :

_images/qualisys_joint_labels_corrected.png

Qualisys to Kinect conversion

In order to compare Kinect and Qualisys recordings, an (arbitrary) conversion system based on joint averaging has been defined. In the following table, joints with an asterisk are joints obtained by averaging Qualisys joints: they are calculated first before being used to create other joints via averaging.

Kinect joint

Averaged joints

Head

HeadTop

HeadFront

HeadLeft

HeadRight

Neck

Head*

SpineShoulder

SpineShoulder

SpineShoulder

ShoulderLeft

ShoulderTopLeft

ShoulderBackLeft

ShoulderRight

ShoulderTopRight

ShoulderBackRight

SpineMid

Chest

BackLeft

BackRight

ElbowLeft

ElbowLeft

ElbowRight

ElbowRight

WristLeft

WristOutLeft

WristInLeft

WristRight

WristOutRight

WristInRight

HandLeft

HandOutLeft

HandInLeft

HandRight

HandOutRight

HandInRight

HipLeft

WaistBackLeft

WaistFrontLeft

HipRight

WaistBackRight

WaistFrontRight

SpineBase

HipLeft*

HipRight*

KneeLeft

KneeLeft

KneeRight

KneeRight

AnkleLeft

AnkleLeft

AnkleRight

AnkleRight

FootLeft

ForefootOutLeft

ForefootInLeft

ToetipLeft

HeelLeft

FootRight

ForefootOutRight

ForefootInRight

ToetipRight

HeelRight

Display the sequence

It is possible to display sequences using the functions in doc:graphic_functions. These functions allow to show the skeleton with or without the joints below the waist (parameter ignore_bottom in most functions). In the case of Kinect recordings, the joints ignored below the waist would be HipRight, HipLeft, KneeRight, KneeLeft, AnkleRight, AnkleLeft, FootRight and FootLeft. In the case of Kualisys recordings, the joints ignored below the waist are ThighRight, ThighLeft, ShinRight, ShinLeft, HeelRight, HeelLeft, AnkleRight, AnkleLeft, ForefootInRight, ForefootInLeft, ForefootOutRight, ForefootOutLeft, ToetipRight and ToetipLeft.