how to "rotate" the objects (trackball rotation)

[guille]

Hello,
I would like to know an easy way of rotate the polygons (when I move them with the mouse) that I am drawing (without GLUT).
The problem is that the rotation has to be referred to the local object coordinate system.
When the object was "upside-down": moving the mouse to the right caused an apparent left rotation and vice-versa.
I have found some information about trackball rotation but I am looking for something easier (without quaternions...?).
THANK YOU http://www.opengl.org/discussion_boards/ubb/smile.gif
::g::

[mango]

If you just adds the mouse movement to the objects rotation do I think it should be right.