Rotation about an Arbitrary Axis:
Rotation around an arbitrary axis is complex but we have already studied how to rotate around a major axis. So we may translate an arbitrary axis to pass through origin, rotate and align along the major axis. Now after performing the needed rotation, rotate and translate back to original position.
In general case, rotation around an arbitrary axis is more complexes. To accomplish this, we ought to define the axis of rotation, i.e. points - P1, - P2 and then do the following:
1. Translate so that rotation axis passes through origin.
2. Rotate so that the rotation axis is aligned with one of the principle coordinate axes.
3. Perform rotation of object about coordinate axis.
4. Perform inverse rotation, i.e. inverse of what has been done in (2).
5. Perform inverse translation, i.e. inverse of (1).