surf is a tool to visualize some real algebraic geometry: plane algebraic
curves, algebraic surfaces and hyperplane sections of surfaces. surf is
script driven and has (optionally) a nifty GUI using the Gtk widget set. 

The algorithms should be stable enough not to be confused by curve/surface
singularities in codimension greater than one and the degree of the surface
or curve. This has been achieved quite a bit. We have drawn curves of degree
up to 30 and surfaces of degree up to 20 successfully. However, there are
examples of curves/surfaces of lower degree where surf fails to produce
perfect images. This happens especially if the equation of the curve/surface
is not reduced. Best results are achieved using reduced equations. On the
other hand, surf displays the Fermat-curves accurately for degree up to 98. 

WWW: http://surf.sourceforge.net/