(bind-func mat4_to_mat3
  (lambda (mat4:float* mat3:float*)
    (pfill! mat3
            (pref mat4 0) (pref mat4 1) (pref mat4 2)
            (pref mat4 4) (pref mat4 5) (pref mat4 6)
            (pref mat4 8) (pref mat4 9) (pref mat4 10))
    void))