I need help to draw an arbitrary surface in TikZ, in order to represent a manifold. I am trying to make something with shade. I manage to get a rectangular surfcace with corners, shaded color, etc but it does not look as good.
Can anyone give me an example and tell me how I can edit it? I do not need something complicated.
Also, is there a manual specifically mentioning how to draw various stuff for diff. geometry?
Thanks a lot.
