Transformation

The Transformation page contains the settings for defining a new global coordinate system. The two changes that can be made to the coordinate system is Translate origin and Rotate coordinate system. By changing these parameters you can in fact move and turn the coordinate system to any position and orientation. The change is always related to the original position and orientation of the calibration coordinate system. In the case of the Fixed camera calibration this means the origin of the survey measurement.

A new calibration file is saved if you apply a new transformation to the current calibration. This file only includes calibration data and no 2D data. Therefore, you must always go back to the first calibration if you need to recalibrate.

To activate the change you must select the checkbox of respective setting.

  • Translate origin: X(mm), Y(mm), Z(mm)

    Enter the new position of the origin of the coordinate system (in mm). The direction of the parameters (X, Y and Z) is always related to the original coordinate system of the calibration.

  • Rotate coordinate system: Roll, Pitch, Yaw

    Enter the new rotation of the coordinate system (in degrees). The rotations always refer to the original coordinate system and they are always applied from left to right. The name of the angles and the rotation axes depend on the Euler angles definitions on the Euler angles page, see chapter Euler angles.

The buttons below the translation and rotation settings can be used to automatically calculate the transformation parameters based on a measurement.

  • Rotate axis to line

    Align the calibration with an axis defined by two markers, see chapter Rotate axis to line.

  • Fetch rigid body

    Calculate the translation and/or rotation values based on the pose of a rigid body. This can for example be used to level the floor or to obtain a repeatable global coordinate system based on a set of three or more reference markers. For more information, see chapter Transform coordinate system to rigid body.

Notes about rotations:

  • If the Euler angles are changed after a transformation, the transformed coordinate system will have the same orientation as before, but the rotation parameters on the Transformation page will change to reflect the new definition.

  • The rotation angles are used to calculate a rotation matrix, which is then used to transform the coordinate system. When the resulting rotation matrix is converted back to rotation angles again it is not necessarily the same angles. This means that the angles that you have entered can change after you have applied it to the coordinate system. For example, if you just enter a pitch of 100 degrees (using Qualisys standard) this will result in the angles roll = 180°, pitch =80°, yaw =180°.

If you use a custom bounding box on the 3D Tracking page, or if you are using a force plate, these will be moved with the transformation and the positions must therefore be re-entered.