Re: Geomview

[slevy]

Probably the easiest way to get something resembling animation doesn't
involve changing the viewer's code, but just running a series of
viewer-language commands that load each file in turn.

For example, if you put the following shell script in a file, say "animate":

#! /bin/sh
while sleep 5; do
    for f in $@ ; do
	if [ -f $f ]; then
	    echo "( geometry fred < $f )"
	    sleep 1
	fi
    done
done

and make it executable:  chmod +x animate
and run it:  animate  file1 file2 ... fileN

it will emit a sequence of lines

	( geometry fred < file1 )
	( geometry fred < file2 )
	... 
	( geometry fred < fileN )

at 1-second intervals, then wait five seconds and play them again.
Obviously you could cut out the "sleep 1" to display things at full
speed, and remove the "while sleep 5; do" and final "done" to
run through only once.

Now you can make the viewer execute these in a couple of ways.

	animate file1 file2 ... | geomview -c -

animate's output is piped to geomview; the ``-c -'' option makes the
viewer read commands from its standard input, i.e. the pipe.

This is easy but a bit inflexible; you can't change the list of files
being animated without stopping the viewer and re-running the whole thing.

You could gain a bit more control over the process by making a "named pipe"
and having geomview read from it while animate writes there:

	/etc/mknod mypipe p		(do this once; the pipe exists
					indefinitely once you create it)

	geomview -c mypipe &
	animate file1 file2 ...  >mypipe

You can then stop, re-run, etc. animate as needed.

I admit this setup allows only rather primitive control over the animation,
but it might be of some use.  Eventually we'll probably add real animation
to geomview itself, but don't know when nor just how it should work.

   Stuart