Making movies with xnbody Edit
written by A. Ernst (email@example.com, August 10, 2005)
- Download the tool "mpeg_encode" (the download area is here) from the UC Berkeley and install it on your machine. Some minor patches in the source code may be necessary!
- Run nbody6 and xnbody. Wait until the online visualisation starts. Select Tools->Animation from the menu. In the Output window, choose a directory, the prefix "try" and the file format "jpeg". In the Record window, choose a frequency (for instance, "30000") and push the start button. Now the program will start producing jpeg files (one every 30 seconds) starting with "try0000.JPEG". Wait until there are enough jpeg files for a movie.
- Copy the binary file "mpeg_encode" into the directory with your jpeg files. This tool requires the pictures to be in .ppm format.
- Write the following shell script named "mkppm" consisting of one
for i in try*.JPEG; do new=`basename $i .JPEG`.ppm; echo $new; convert $i $new; done
This will convert all your JPEG files to .ppm files. You can also use djpeg instead of convert, which is included with mpeg_encode:
for i in try*.JPEG; do new=`basename $i .JPEG`.ppm; echo $new; djpeg $i > $new; done
- Create a parameter file for mpeg_encode (named "parfile", for instance), which looks like this:
# mpeg_encode parameter file PATTERN I OUTPUT test.mpg GOP_SIZE 30 SLICES_PER_FRAME 1 REFERENCE_FRAME ORIGINAL BASE_FILE_FORMAT PPM YUV_SIZE 352x240 INPUT_CONVERT * INPUT_DIR . INPUT try*.ppm [0000-0100] END_INPUT ERROR MAD PIXEL FULL RANGE 8 PSEARCH_ALG EXHAUSTIVE BSEARCH_ALG SIMPLE IQSCALE 31 PQSCALE 10 BQSCALE 25
Modify this file accordingly: In the line starting with "try*.ppm" insert the start and end number of your image files.
mpeg_encode parfilein the command line and press Enter.