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From: Andy Little (andy_at_[hidden])
Date: 2006-06-12 10:03:23

"me22" <me22.ca_at_[hidden]> wrote in message
> On 6/11/06, Andy Little <andy_at_[hidden]> 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 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 :-)

Andy Little

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