Thanks a LOT! I was asking on GLUT because I wanted to try the glut's drawing primitives like solidTeapot and so on... I found that I must supply the LIBS directive to qmake this way:

Qt Code: 
  1. LIBS += -framework GLUT
To copy to clipboard, switch view to plain text mode 

Besides that, why does this code need two trackballs instead of one? Actually the Boxes example, uses three, and I'm still wondering why. I have the same question on the conjugate() call on the rotation's quaternions, I'd like to know what sense makes that call here.