Re: [boost] [Review][PQS] Review ends

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

"me22" <me22.ca_at_[hidden]> wrote in message 
news:fa28b9250606111226m1809c81ai14d096e010e718f1_at_mail.gmail.com...
> 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 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