[ODE] Quaternion performance issues?

[Bill Sellers]

Hi All,

I've implemented some custom code for applying forces and it's  
working fine. However I've just been doing some profiling and it it  
takes quite a large chunk of the simulation time doing various  
rotations. I've implemented these rotations using quaternions getting  
the values from dBodyGetQuaternion but obviously I could just as  
easily redo the whole thing using matrices and dBodyGetRotation. Has  
anyone any opinion about whether it would make any difference to the  
calculation time? Is there any overhead in ODE associated with these  
calls or does ODE maintain both sets of rotation information for a  
body, and is there much difference in calculation speed of quaternion  
rotations versus matrix ones?

Cheers
Bill

PS. The main reason I prefer quaternions is that they are usually  
fairly unambiguously documented. With matrices I always have to dig  
through lots of literature to find out whether they are stored in row  
major or column major format. It's a little thing I know but I find  
3D rotations hard enough to debug as it is without any extra layers  
of uncertainty.