"me22" <me22.ca@gmail.com> wrote in message news:fa28b9250606111226m1809c81ai14d096e010e718f1@mail.gmail.com...
On 6/11/06, Andy Little <andy@servocomm.freeserve.co.uk> wrote:
OK. So going back to the original point. The intent in PQS is to use a quaternion solely for representing a rotation in 3D space. Putting quaternion in a 3D namespace makes sense to me from that viewpoint and should help to clarify its intended purpose.
In that case I think it should be called unit_quaternion to emphasise the point. It would also make it clear that the implementation is ensuring and assuming that w*w+x*x+y*y+z*z is very close to 1.
OK. This functionality will surely depend on the implementation of vect * quat ? In boost::quaternion the quaternion seems to be normalised during the calculation AFAICS. See <libs/math/quaternion/HS03.hpp>. I have to confess that I don't know enough about quaternions to speak with authority. As Janek Kozicki brought up yade http://yade.berlios.de/. My current plan is to look at that as an example useage. Again only for rotations. I'm not even sure yet how I can test the calculations on quaternions. I need to understand more about how they are constructed, starting maybe from an [axis-vector,angle] type maybe, simply because I can visualise that easier than 4 dimensions :-) regards Andy Little