Gnuplot is a portable command-line driven graphing utility for Linux, OS/2, MS Windows, OSX, VMS, and many other platforms. The source code is copyrighted but freely distributed (i.e., you don't have to pay for it). It was originally created to allow scientists and students to visualize mathematical functions and data interactively, but has grown to support many non-interactive uses such as web scripting. It is also used as a plotting engine by third-party applications like Octave. Gnuplot has been supported and under active development since 1986.
A simple particle system physics engine for processing. I've designed this to be application / domain agnostic. All this is supposed to do is let you make particles, apply forces and calculate the positions of particles over time in real-time. Anything else you need to handle yourself.
M. Goedicke, T. Meyer, and G. Taentzer. Proc. Int'l Workshop on Theory and Application of Graph Transformation (TAGT), volume 1764 of Lecture Notes in Computer Science, Springer-Verlag, (2000)
K. Sugiyama. Series on software engineering and knowledge engineering ; 11 World Scientific, Singapore u.a., (2002)Kozo Sugiyama. Literaturverz. S. 203 - 212. $5GBV.