Jep is
a mathematical equation parsing and evaluation library written in
java. It features fast evaluation, a configurable architecture
allowing custom syntax, support for BigDecimal, complex numbers and
vectors It is developed by Singular
Systems

GWT-Jep is a port of Jep to run in javascript and has all the
features of Jep apart from a small set of changes
necessary for javascript compatibility. It is compiled from Java using
the Google Web
Toolkit. It is available as a seperate package from SingSurf.

The parametrized surfaces application draws surfaces in 3D. It uses the three.js for the 3D graphics.
Equations can be specified either as a single height function: