Web technical background information

The Javascript animated pendulum page was originally written in order to see, whether Javascript can be used to solve numerically ODE's for illustration purposes. ( The first test page ). We like javascript because of its simplicity and because it is opensource par exellence.

The individual pictures for the Javacript animation were generated with Povray 3.1 under the Linux operating system (currently Mandrake 6.0 ). A shellscript which uses the netpbm routines postprocessed each picture for the web. For example, colors were reduced to 16 colors with ppmquant to keep the files small. The information pages are written in LaTeX, translated into HTML using LaTeX2html and postprocessed by hand. The figures were done in Povray sometimes assisted by Mathematica . The animated gifs were generated with Unix tools (like gifmerge, gifsicle) using also the Gimp . Sometimes files got squezed with Fireworks on a Power Macintosh for optimization, which can bring several times smaller GIF files. The picture beside shows a snapshot of a Povray picture in color used for building the Poincare map animation. The eye above was built in Povray for an effect in the mainpage . It even got a lense and an iris built in.

The phase space pictures of the pendulum were generated with Mathematica with the command


ContourPlot[y^2/2 + 2*(1-Cos[x]),{x,Pi,3*Pi},{y,-4,4}]

(but different default parameters). Each wire (representing an orbit of the Pendulum differential equation) is a union of 120 cylinders. Colored pictures of this size would give way too large animation files.