!! used as default html header if there is none in the selected theme.
This page uses the technique of ray tracing (via
Povray) to plot algebraic surfaces,
i.e., surfaces defined by implicit algebraic equations.
This technique gives excellent results, but requires a relatively
important amount of time for the computation. You are therefore asked to
be patient, and not to ask for plots of too high quality (size and
fluidity of animation).