Calibrate Vicon cameras

You specify settings for the calibration of Vicon cameras on the Calibrate tab, in the Calibrate Cameras section.

The Vicon camera calibration process describes the capture volume to the system, enabling Tracker to determine the positions, orientations, and lens properties of all the Vicon cameras. Tracker uses this information to produce accurate 3D data. During the camera calibration process, Vicon Tracker creates a calibration parameters (.xcp) file. This file contains the calibration settings and threshold data specified for the Vicon cameras in your Tracker system and is used when data from these cameras is processed. An .x2d file containing the latest calibration data, of the format LatestCalibration yyyymmddnnnnnn.x2d, is also saved in the same location as the .x2d containing the recorded trial data.

To perform a Vicon camera calibration, you need a dynamic calibration object, which is supplied with your Vicon system.

To calibrate Vicon cameras in Tracker:

1. Do one of the following:

   • If you want to calibrate only some of the cameras, on the System tab in the Resources pane, expand the Vicon Cameras node and select the Vicon cameras that you want to calibrate;
   • If you want to calibrate all cameras, go straight to the next step.
2. On the Calibrate tab, expand the Calibrate Cameras section and from the Wand drop-down list select the type of dynamic calibration object you are using.

3. View or change the settings for the required parameters (if required, click Show Advanced to reveal additional settings), ensuring that you select the appropriate option from the Calibration Type list: Full Calibration or Calibration Refinement.

   Tip: If you have already performed a full calibration, Calibration Refinement is selected by default, as this will normally be the most appropriate option. (For more information, see Understanding calibration types.)

4. In the Calibrate Cameras section, click Start.

   All Vicon cameras are selected and a separate Camera view pane is displayed for each one. The camera calibration process starts, and the Start button switches to its Stop setting.

5. In the capture volume, wave the calibration wand throughout the area where you intend to capture 3D data, ensuring that the markers on the calibration object are visible to the cameras. Vicon Tracker begins to capture wand wave data.

6. In each Camera view pane, check the display of colored lines identifying wand frames, ensuring that a good number of wand frames are spread across the intended 3D capture volume.

   Tip: If no cameras are visible in the Camera view pane, make sure they are selected on the System tab in the Resources pane.

   If any optical camera does not capture wand data during a wand wave, select the relevant camera on the System tab, look in the Settings section of the Properties pane, and ensure you have set the Grayscale Mode to Auto.

7. On the Calibrate tab, in the Camera Calibration Feedback section, check the Wand Count values returned for each Vicon camera.

8. In the Calibrate Vicon Cameras section, click Stop. Vicon Tracker automatically starts processing the camera calibration data.

   (If you selected the Auto Stop option in the Parameters section, Tracker automatically stops the calibration process when sufficient calibration information has been acquired.)

9. In the Camera Calibration Feedback section, monitor the progress bar until the camera calibration process is complete and review the Wand Count and Image Error data. As a general guideline, Tracker typically takes 15-60 seconds to complete its calculations for a typical Vicon system setup. When the Vicon camera calibration has successfully completed, it is automatically saved to an .xcp file.

   Tip: Because calibration feedback values are based on factors such as the size of the capture volume and the camera lens type, it is not possible to provide general guidelines on typical or acceptable ranges. Therefore, to determine the optimal values for your Vicon system, shortly after the system is installed establish a baseline against which you can compare future daily calibration values.

For more information, see:

• Camera calibration parameters
• Camera calibration feedback
• Setting the volume origin
• Changing the volume origin
• Managing camera calibrations
• Improve volume scaling and set a fixed origin