Animation with OpenGL and CAPI

Well I'm stranded, I get the OpenGL example compiled but do not
understand on how OpenGL and CAPI work together. I can write an own
display function, but in this I assume I have to use a timer which
waits for a while and than redisplay the moved element is that right?

Does that mean I have to write something simular ot the ballon stuff
for CAPI?

(defun animate-balloons (sky)
  (with-slots (timer) sky
    (setf timer (mp:make-timer 
                 #'(lambda (sky)
                     (capi:execute-with-interface
                      sky
                      #'(lambda (sky)
                          (with-slots (balloons) sky
                            (dolist (balloon balloons)
                              (animate-balloon balloon))
                            ))
                      sky))
                 sky))
    (mp:schedule-timer timer 0.0 0.05)))

It would be nice if someone had an idea for this simple problem. Show
a rotating triangle.

Regards
Friedrich