Introduction
The purpose of this application is to enable visualization of the soft tissue artefact (STA) of the humerus and scapula. The position and orientation of the humerus and scapula were recorded via biplane fluoroscopy (~1 mm and ~1 deg accuracy). The skin marker positions were recorded using a 10-camera Vicon system.

Animation Control
The play/pause button and slider bar at the bottom of the page provide control of the animation. The frame number shown to the right of the slider bar corresponds to the bi-plane fluoroscopy frame number.

Marker Set
The scapula marker cluster is comprised of 4 markers attached to key landmarks on the scapula. The humerus marker cluster is also comprised of 4 markers. These markers are affixed on a rigid plate, which is attached to the humerus using an arm band. For the humerus and scapula marker clusters, each marker is assigned a color (red, green, blue or yellow) and its position is computed using two methods. In the first method (represented by a solid marker) the marker position is derived directly from the Vicon system. In the second method (represented by a mesh marker) the marker position is computed by rigidly attaching the marker to its corresponding segment (humerus or scapula) in the first frame. Therefore, the mesh marker represents the marker position without STA. Grey markers represent markers attached to the torso, forearm, or hand of the subject. The forearm and hand markers are not shown by default. The humerus also has a fifth marker attached to the lateral epicondyle, however this marker is not considered as part of the humerus marker cluster (so it's shown in grey).

Visualization Aids
The markers within a marker cluster are connected together via solid lines. This aids in visualizing how the entire marker cluster is deforming. In addition, solid and dashed lines - corresponding to solid and mesh markers, respectively - trace the path of each marker throughout the animation.

Configuration Parameters
In the upper-right hand corner of the application a set of configuration parameters is available. By clicking Open Controls, the marker, trace, and marker cluster visibility can be adjusted.

3D Controls
Left-clicking and dragging rotates around the humerus and scapula. Right-clicking and dragging pans the scene. The scroll-wheels zooms in and out.