Does anybody know of any easy-to-understand tutorials on what quaternions are and how they can be used to perform 3D rotations? Most tutorials I have found are very mathematical and do not explain them enough for me to understand Thanks for your help.

http://www.gamasutra.com/features/19980703/quaternions_01.htm

have fun

Thanks, that tutorial really helped. Just to check that I understand it, if I want to rotate a point around an axis passing through the origin then will the quaternion be:

q = (cos a/2, u sin a/2)

where "u" is a 3D vector defining the axis from the origin and "a" is the angle of rotation? Does this sound right?

Thanks.