function rotate(rate)
  [a e] = view;
  a = a + rate(1);
  e = e + rate(2);
  view(a, e); 
  drawnow;
  a = a + rate(1);
  e = e + rate(2);
  view(a, e);
  drawnow;
  a = a + rate(1);
  e = e + rate(2);
  view(a, e);
  drawnow;
  a = a + rate(1);
  e = e + rate(2);
  view(a, e);
  drawnow;