Motion Capture Setup

Glove

Human fingers (index, middle, ring, and little finger) have three joints. However, isolated joint movements are not always possible. In particular, the last two finger joints often move together. While it is very difficult to isolate movements of the last finger joints (distal interphalangeal, between intermediate phalanges and distal phalanges), it is possible to isolate movements of the proximal interphalangeal joints (between proximal phalanges and intermediate phalanges) and the metacarpophalangeal joints (between metacarpal bones and proximal phalanges).

_images/finger_tendons.png

Tendons of finger flexors and extensor. Yellow: tendons of flexor digitorum profundus attach to distal phalanges. Red: tendons of extensor digitorum also attach to the distal phalanges. Orange: tendons of the flexor digitorum superficialis attach to the intermediate phalanges.

We conclude that it is enough to attach two markers to the fingers to track their state of flexion or extension. Furthermore, with these two markers we also can measure their state of abduction or adduction.

We used the following labelled markers on the glove to record the datasets used in the paper:

  • Hand pose: hand_top, hand_left, hand_right

  • Per finger (thumb, index, middle, ring, little): [finger]_middle, [finger]_tip

The following shows the configuration of our glove for the right hand:

_images/glove.png

The figure is based on this work of Mariana Ruiz Villarreal (LadyofHats); retouches by Nyks.

Tracked Objects

In addition, we attached motion capture markers to objects to track their poses and to transfer object manipulation trajectories into an object-relative coordinate system. The following image shows these objects.

_images/objects.png

The marker configuration and the definition of frames based on markers is implemented and documented in hand_embodiment/mocap_objects. We assume that the z-axis points up for all objects with only two markers. Meshes for visualization are available here and transformations between marker frames and the mesh frames can be found in hand_embodiment/vis_utils.