[Plib-users] Quaternion rotations

[Bob H. <ham...@ho...>]

Hi,

I downloaded the latest CVS version of plib and found the new quaternion =
demo (with the two rotating cubes).  This demo rotates the quaternions =
around the world axes (using sgRotQuat(..) ).

How can I use quaternions to rotate an object around it's axes?  I've =
got an idea that might work.  Say I want to rotate around the x axis, I =
convert my quaternion to a matrix, extract the first column and use this =
as the vector passed to sgRotQuat.

Ie.

sgMat4 tmpMat ;
sgQuatToMat ( tmpMat, myQuat ) ; // Make the matrix from the quaternion
sgRotQuat ( myQuat, 5.0, tmpMat [0] ) ; // Rotate 5 degress around =
objects x axis

Since we're only using the first row of the matrix the above can =
probably be simplified.

Will this work? Is there anything else I need to know (stuff that might =
bite me in the ass?) ?