Quaternion Constructor (Double, Double, Double, Double)
Initializes a new instance of the Quaternion structure.
Assembly: PresentationCore (in PresentationCore.dll)
For the axis (x, y, z) and angle of rotation theta, the w value for the quaternion is:
w = cos(theta/2)
Note that if you use the Vector3D constructor, the fourth parameter is the angle, in degrees, and the w calculation is performed for you.