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
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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.