Because of the complicated nature of quaternions, it is not always feasible to specify a quaternion rotation directly. Instead, you might want to specify a set of three Euler angles, or perhaps a rotation around an arbitrary axis, particularly if you need to retrieve input from a user. An average human being would have a hard time trying to enter a rotation quaternion and would much rather enter a set of Euler angles. For purposes of transforming vertices or other game components, you may require a rotation matrix instead of a quater­nion. This is no problem; you can convert between all of these ele­ments with very little effort. The next section begins with quaternion to matrix conversion.