Camera positioning

Cameras must be mounted firmly on tripods or other stable structures, which isolate the camera from movements or vibrations of any sort.

3D motion capture

To capture 3D data the camera system must consist of at least 2 cameras. The guidelines below can be used to set up a camera system.

  • The best possible setup for a 3D motion capture system is to position it so that all cameras can see the L-shaped reference structure during the calibration, see chapter Calibration of the camera system.

    The cameras can be positioned so that just two of the cameras are able to see the calibration reference object. The rest of the cameras must then overlap each others field of view (FOV) to be able to calibrate the system. For this setup QTM will automatically use the Extended calibration method, see chapter Extended calibration.

  • To reconstruct 3D data, at least two cameras must see each marker during the measurement. Therefore, it is best to position the cameras so that as many cameras as possible see each marker during the measurement.

  • The angle of incidence between any two cameras should ideally be more than 60 degrees, but at least 30 degrees. The accuracy of the 3D data calculated from only two cameras placed at less than 30 degrees can degrade below usable levels.

  • In order to avoid unwanted reflections, position the cameras so that every camera’s view of flashes from other cameras is minimized. E.g. put the cameras above the measurement volume so that the cameras have an angle of about 20 degrees in relation to the floor.

  • Obviously the cameras must also be positioned so that they view the volume where the motion of the measurement subject will occur. Mark the volume by putting markers in the corners of the base of the measurement volume. Then make sure that all cameras can see all of the markers by looking at a 2D view window in preview mode. Preferably, the cameras should not see much more than the measurement volume.

2D motion capture

In 2D motion capture just a single camera is needed, which is positioned perpendicular to plane that is captured.