Animations using Xmgrace

General procedure

The general idea is to write a program (program.exe) in any language (e.g., in C or Fortran) that prints comands of xmgrace together with points. In particular one uses the comands
"@kill s1" - to kill set 1 when passing from frame to frame
"@redraw" - to redraw everything
"@sleep 1" - to make it sleep for 1 second (introduces delay)

The file looks at the end like [example.agr]

The xmgrace nicely animates this file using the following comand:
cat example.agr | xmgrace -pipe -noask -autoscale none -fixed 1200 800 -timestamp -nosafe -geometry 1200x1200
It is of course also possible to run directly the program (see below):
program.exe | xmgrace -pipe -noask -autoscale none -fixed 1200 800 -timestamp -nosafe -geometry 1200x1200

To generate an animated gif, one asks the Xmgrace to plot .png or .ps files of each frame. One example of such file is [example_print.agr] (check that the directory "fig/" exists).

In order to join them in a single gif file one should use a suited program, e.g., in linux usually one can use
convert *.png animation.gif

The animation is now huge. You can optimize and introduce some different velocity of the frames using
gifsicle -d 1 -O animation.gif -o animation_d20.gif

Example: mushroom billiard

All data seen in the animations are contained in files (the programs to generate the dynamics of the billiard is not included here).
The (x,y) components of the trajectory at each instant are at [[http://www.pks.mpg.de/~edugalt/hamiltonian/download/ trajectory.dat]] and [trajectory2.dat].
The frame of the mushroom table is at the file [frame.dat].

The program that reads these files and plots them inside Xmgrace comands was written in C and is given as [mus_grace.c]. It has the following entries
sintaxe: mus.exe [points] [line] [frames] [file]
points=[1 or 2] | line=1 yes, 0 no | frames=[1,10^5] file=trajectory

A typical command to animate with the grace would be thus
./mus.exe 2 1 300 trajectory | xmgrace -pipe -noask -autoscale none -fixed 1200 800 -timestamp -nosafe -geometry 1200x1200

This was condensed in the script <a href="anime_mus.exe"> anime_mus.exe</a> and the comand simplified thus to:
./anime_mus.exe 2 1 300 trajectory

To generate gif animator, uncomment the appropriate lines in the program "mus_grace.c" above and create the directory "fig/". Then use
convert *.png animation.gif

Do yourself:

Save all files of the [directory].

Compile mus_grace.c to mus.exe
gcc -o mus.exe -lm mus_grace.c

Make the anime_mus.exe an executable file
chmod 755 anime.exe

Run the following command
./anime_mus.exe 2 1 300 trajectory

If you were successfull you should see on Xmgrace screen the animation below.

To generate the gif animation, uncomment the appropriate lines in the C program and follow the instructions above