During calibration, the Vicon Evoke camera calibration process calculates the physical position and orientation of each Vicon camera in the capture volume based on the movement of a calibration object (usually a Vicon Active Wand). The process describes the capture volume to the system, enabling Evoke to determine the physical positions, orientations, and lens properties of the Vicon cameras in the capture volume, and to correct for any lens distortion. Evoke uses this information to produce accurate 3D data.
As part of the calibration process, you can set the volume origin in Evoke. Evoke measures the position of the calibration object and uses this information to identify the origin of the world and its horizontal and vertical axes. These volume origin and axes are referred to as the global coordinate system. The global axes' coordinates are given in the form (x, y, z), where x is a horizontal axis, y is the horizontal axis perpendicular to x, and z is the vertical axis.
When a camera calibration process has completed, Evoke saves two identical calibration parameters (.xcp) files and two corresponding identical raw camera data (.x2d) files to a calibrations folder ( C:\ProgramData\Vicon\Calibrations ). The .xcp contains the calibration settings and threshold data specified for the Vicon cameras in your Evoke system and is used when data from these cameras is processed. The difference between the two .xcp and two .x2d files is in their naming convention within the calibrations folder and how they are automatically managed.
- LatestCalibration: These .xcp and .x2d files are replaced after each completed calibration process and are used for the current processing of camera data.
- LatestCalibration yyyymmddnnnn: Up to 10 unique .xcp and .x2d files of this nomenclature are stored in the calibrations folder. The oldest .xcp and .x2d are overwritten by the latest calibration.
You specify settings for the calibration of Vicon cameras in the Camera Calibration panel.
Calibration is a necessary process to enable accurate tracking. To understand the cadence at which you should perform a calibration, see Maintain system health. When calibrating, you can perform the level of camera calibration that suits your requirements: a full camera calibration or a calibration of only a selected camera (for more information, see Calibrate a selected camera).
When you first connect up your Vicon system and start Vicon Evoke, notice that in the System panel and in the Cameras view, icons give you feedback on the current status of the cameras. The cyan icon indicates that although the cameras are connected, they are not yet calibrated.
To calibrate your Vicon cameras, complete these procedures in order:
Before you use your Vicon system to calibrate or track, ensure that cameras have fully warmed up to a stable operating temperature. For most cameras the warm-up time will be at least 30 minutes (a minimum 30–60 minute warm-up period is recommended) but for environments with lower ambient temperatures, it could take up to 90 minutes.
To find out whether a camera has reached its steady-state temperature, use the Temperature section in the System Health Report. For more information, see Understand the System Health Report
To display a layout of panels and views that is optimized for calibration, consider using the Camera Calibration view type (see Load and save window layouts). This displays only the System and Camera Calibration panels, while maximizing the Workspace to display all the camera views.
For further information about camera calibration, see also: