xd3d is a simple scientific visualization tool designed to be easy to learn.

It can plot 2d and 3d meshes, with shadowing, contour plots, vector fields,
iso-contour (3d), as well as 3d surfaces z=f(x,y) defined by an algebraic
expression or a cloud of points. It generates high quality vector PostScript
files for scientific publications and still or animated bitmap images.

It includes the graph plotter xgraphic.

WWW: http://www.cmap.polytechnique.fr/~jouve/xd3d/
