Camera System and VRPN

System Overview

The VRPN system operates on IP address 192.168.0.120 port 3883/

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.

Computer Configuration

Windows Settings

It appears that Tracking Tools has an incompatibility with some updates provided with Windows 7. The problem is the VRPN server is unable to consistently maintain an update interval of 10ms position packets (the software still gets position at 10ms intervals, but it is not reported over VRPN at that rate).

To fix this, the Tracking Tools software must be run on a non-updated version of Windows 7 (it appears updates released sometime in 2015-2016 broke the VRPN function). So Windows Update should be disabled.

Additionally, system restore should be enabled (for both settings and files), so that in the future if anything happens the system can be reverted to a known-working state.

Firewall Settings

The Windows computer hosting the VRPN server must have port 3883 both TCP and UDP protocols opened in order to work.

Additionally, all clients should have those two ports opened as well. Since VRPN appears to create connections in both directions.