TEACH MAKE_XWD                                  Aaron Sloman March 1999

How to make your sim_agent program dump a succession of images
using the unix xwd command. See MAN XWD

The following items of information were extracted from TEACH SIM_DEMO

As a step towards making a movie of your your sim_agent program running
you can modify the program so as frequently to take a snapshot of the
state of the window in which you are displaying the simulated world.
This is done by using xwd to create a sequence of image files, which
might be called something like pic1.xwd, pic2.xwd, pic3.xwd, ....

WARNING: this can use up many megabytes of file space, especially if
your window is a large one.

After that other tools may be used to combine these image files into
a movie file, e.g. mpeg_encode (if that is available). Alternatively you
may be able to view the xwd files directly by giving the file names
to the "xv" program. See MAN XV

For examples of movies created in this way see:

    http://www.cs.bham.ac.uk/~axs/cog_affect/sim_demo

You can also access those demos from the overview web page
        http://www.cs.bham.ac.uk/~axs/cog_affect/sim_agent.html


HOW TO DUMP THE IMAGE FILES

1. Create some global variables to control how images are dumped

global vars
    ;;; This variable should hold the name of window to be dumped
    ;;; in a pop-11 string. It will be given as argument to xwd
    graphic_window = 'MYWINDOW',

    ;;; A variable which is false or integer, to control frequency
    ;;; of dumping. If the value is N, the dumping should happen
    ;;; every N cycles of the scheduler. If it is false, don't do any
    ;;; image dumping
    image_dump_frequency = 5,
    ;;; or
    image_dump_frequency = false,

    ;;; names of image files will be created from this word via
    ;;; gensym and the suffix '.xwd', e.g. mysim1.xwd, mysim2.xwd...
    imagefile = "mysim";


2. Create a version of one of the trace procedures or methods in
SIM_AGENT which will be invoked at regular intervals. Make it decide,
under the control of the variable image_dump_frequency whether or not
to create a dump of the current window.

A suitable procedure  to use for this purpose would be
     sim_scheduler_pausing_trace(objects, cycle);

which is called at the end of every time slice, with the list of objects
and the cycle number. See
    HELP SIM_AGENT/sim_scheduler_pausing_trace
    HELP SIM_HARNESS/sim_scheduler_pausing_trace
    LIB SIM_HARNESS/sim_scheduler_pausing_trace

define vars procedure sim_scheduler_pausing_trace(objects, cycle);
    ;;; user definable

    ;;; code for dumping a snapshot every N cycles
    if isinteger(image_dump_frequency)
    and cycle mod image_dump_frequency == 0 then
        sysobey('xwd -name ' >< graphic_window >< ' > '
            ><
                gensym(imagefile)><'.xwd');
    endif;

    Now add other trace commands, e.g. copied from
    LIB SIM_HARNESS

enddefine;


See HELP SIM_HARNESS for more information on tracing methods.

3. Run the demo and let it create image files using xwd. This will
use up huge amounts of disk space, so beware.

4. At the end combine the image files into a movie, or simply use
them as they are.


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--- Copyright University of Birmingham 1999. All rights reserved. ------