DRAWPARTIALPATCH draw surface patch, with 2 parametrized surfaces.

   usage :
   drawSurfPatch(u, v, zuv)
   where u, v, and zuv are three matrices the same size, u and
   corresponding to each parameter, and zuv being equal to a function of u
   and v.

   drawSurfPatch(u, v, zuv, p0)
   If p0 is specified, two lines with u(p0(1)) and v(p0(2)) are drawn on
   the surface


   ---------

   author : David Legland 
   INRA - TPV URPOI - BIA IMASTE
   created the 24/05/2005.

Package: matgeom