Define an arbitrary, logical quad of points in 2D(xy) space.nx and ny specify the number of points in the x and y directions. The four corners of the quad are then listed in counter clockwise order ( the normal to the quad points is defined using the right hand rule and the order of the points).


quadxy/nx ,ny /x1,y1,z1/x2,y2,z2/x3,y3,z3/x4,y4,z4/