3           2             2      3
Bézier(t) = y (1-t)  + 3y (1-t) t + 3y (1-t)t  + y t 
             1           2            3           4
      \prime            2                2           
Bézier      (t) = d(1-t)  + 2e(1-t)t + ft            
      \prime\prime
Bézier            (t) = w(1-t) + zt