MOVIES!

Making movies is surprisingly difficult. No matter what language you use, apparently true movie files can only be made by stringing together images, i.e. there is no native movie-producing feature. Gnuplot can do some simple animations but to do anything sophisticated you need to start delving into variables, and for that I switch to a real language.

So, I returned to python. As usual, it took no more than a few hours of coding and learning to come up with something. But it bothers me that it took that long: I still think python is most deficient in its failure to create a default column-text reader like 'readcol' in IDL. I can't complain that much, though: I wrote my own in about 5 minutes.

Anyway, the key is to use the .set_xdata and .set_ydata functions of a plot to update a canvas. I still don't have nearly as high a plotting speed as I'd like, but it works alright if I don't display to screen. Probably a different backend would be more effective but I don't like to mess with backends.

I use savefig(filename,dpi=50) to reduce the image quality so that it's easier for the animator to handle.

ImageMagick's convert can be used to stitch any kind of image into a movie given that you've installed an mpeg2 encoder (fink gave me mpeg2vidcodec ). The command is very simple:

convert -size 300x300 *.png movie.mpg


I had to use a smaller image size because a series of 1000x12kb files somehow chomped ~6-8 GB of RAM and swap space.