[ggt-devel] Quaternion bug?

[Justin H. <ja...@vr...>]

I think I may have found a problem with the multiplication of quaternions.

   // +90 degree rotation about the Y-axis
   gmtl::Quatf quatA = gmtl::make<gmtl::Quatf>(gmtl::EulerAngleXYZf(0,gmtl::Math::deg2Rad(90.0), 0));

   // +90 degree rotation about the X-axis
   gmtl::Quatf quatB = gmtl::make<gmtl::Quatf>(gmtl::EulerAngleXYZf(gmtl::Math::deg2Rad(90.0), 0, 0));

   // Starting with a point on the X-axis
   gmtl::Point3f point( 1, 0, 0 );

   quatA *= quatB;

   point *= quatA;

Now the point should be pointing along the Y-axis, but it is actually (0,
-1, 0), pointing straight down.

Is this a bug, or am I making some bad assumptions about how quaternion 
multiplication should work?

justin

-----------------------------------------
Justin Hare  <ja...@vr...>
Virtual Reality Applications Center
Iowa State University, Howe Hall
http://www.vrac.iastate.edu/~jahare
-----------------------------------------