Camera System and VRPN

Calibrating The Cameras

Setting the Ground Plane

In order to setup the axis system for the camera system, the ground plane tool needs to be used. It has 3 trackables on it, and form an L shape. The negative Z axis is marked by the arrow (so it is negative in that direction). The X axis is the other arm.

To orient it, place it so that the short leg of the L faces east (towards the whiteboards), and the long leg pointing towards the ceiling. In order to get this oriented, it needs to be supported as shown in the image below. When aligning it, also use the level and make sure the long leg is perpendicular to the floor (it may be necessary to prop it up to make it perpendicular).

Once the tool is set, select the three trackables in the software window. Then inside the "Ground Plane" tab, click on the "Set Ground Plane" button to create the axis system.

Tracking Tools Software

Angular Display

The Tracking Tools software includes a display of the trackable's current position (X,Y,Z and attitude). The X, Y, Z values displayed are relative to the camera system's coordinate axis. The attitude displayed is in Euler Angles relative to the camera's coordinate system (its inertial frame). The sequence of Euler angles it uses to convert into these angles is not the Yaw-Pitch-Roll (Aerospace) sequence.

Resetting Orientation

The camera system Tracking Tools software includes a feature to "Reset Orientation" of the currently selected trackable. This feature will only bias the angular position (basically subtract off the current values from the calculated angles), and will not rotate the coordinate system of the trackable to match the new orientation. This feature cannot be used to modify the coordinate system.