How to use Euler angles

Euler angles (rotation angles) are the way that QTM shows the rotation of a 6DOF body and skeleton segments. It is also how you enter any rotation that should be applied to a global or a local coordinate system. It is therefore important to understand how Euler angles work to be able to use 6DOF data correctly.

Euler angles are used to represent rotations in the user interface of QTM. Internally, rotations are represented by rotation matrices in QTM. This means that changing the Euler angles definition only affects the way rotations are displayed and exported. The rotation angles are converted according to the calculations described in chapter Calculation of rotation angles from the rotation matrix (Qualisys standard). The same calculations are then used to acquire the measured rotation angles, since they can be more directly interpreted and visualized by the user.

When you change the Euler angles definition that change will be effective immediately everywhere in QTM. This means for example that if you open a file after you have changed the definitions it will be displayed using the new definitions and not those used when the file was saved. It also means that the angles on the Transformation page will change to reflect the rotation of the global coordinate system with the new definition.

In QTM you can define the Euler angles as any possible rotation of a right-hand coordinate system, see chapter Euler angles. By default QTM uses the Qualisys standard definition, which is described in the chapter Rotation angles in QTM.