%% produit vectoriel de deux vecteurs 3d /vectprod3d { %% x1 y1 z1 x2 y2 z2 6 dict begin /zp exch def /yp exch def /xp exch def /z exch def /y exch def /x exch def y zp mul z yp mul sub z xp mul x zp mul sub x yp mul y xp mul sub end } def