_g_e_o_m_x expects the 4x4 matrix which contains the x coordinates of the 16
control points of the patch.
_g_e_o_m_y expects the 4x4 matrix which contains the y coordinates of the 16
control points of the patch.
_g_e_o_m_z expects the 4x4 matrix which contains the z coordinates of the 16
control points of the patch.
DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
ppppaaaattttcccchhhh draws a surface patch using the current ppppaaaattttcccchhhhbbbbaaaassssiiiissss, ppppaaaattttcccchhhhpppprrrreeeecccciiiissssiiiioooonnnn,
and ppppaaaattttcccchhhhccccuuuurrrrvvvveeeessss which are defined earlier. The control points _g_e_o_m_x,
_g_e_o_m_y, _g_e_o_m_z determine the shape of the patch.
The patch is drawn as a web of curve segments. Each curve segment is
approximated by a sequence of straight lines. All lines use the current
linestyle, which is reset prior to the first line of each curve segment,
and continues through subsequent lines in each curve segment. Other line
modes, including depthcueing, line width, and line antialiasing, also
apply to the lines generated by ppppaaaattttcccchhhh.