Now there are two nodes (x1,y1,z1), (x2,y2,z2). I would like to draw a cylinder. The base''s center is (x1,y1,z1), the top''s center is (x2,y2,z2). How can I do that? I glTransfer(x1,y1,z1) and then glRotatef an angle. and then gluCylinder. but I don''t know how to caculate the angle. Thank you.