This archive contains the following files:

	README		This file

	GNU-GPL		The Gnu General Public License which describes the
			allowable use of the programs enclosed

	rainsim.c	Rainsim version 1.0, a program for generating
			a particle system of drops and propagating them
			over time

	Makefile	A makefile for compiling rainsim.c

   This program generates a set of objects (which are included in the
file raindrop.inc; a sample file has been included).  These objects mimic
falling rain, as the program generates random drops and makes them fall
over time.

   This program works as follows.  It should be started with a single
number as the argument -- this number is the number of time steps that
must elapse before the simulation writes anything to disk.  To start at
the beginning of a storm, just do:

   rainsim 1 &

   The program should be run in the background so that the console can
be used for other things.

   Depending on the initial time given to the program, the simulation may
need to run for a few moments to run up to the desired frame.

   Once the simulator reaches the desired frame, it will halt without
writing anything to disk.  This is the intended behavior!  In order to
cause it to write to disk, it must be sent a SIGUSR1 signal.   This can
be done with the  kill  command as follows:

   kill -USR1 <pid>

   where the process id (pid) can be found using ps -x.

   A sample POVray .ini file is included, which shows how Pre_Frame_Command
can be set to create a new frame for an animation.

   Here is a typical use of the rainsim program:

      1. Start the program at some frame

		rainsim 1 &

      2. Wait for the simulator to stop (using top or ps to see when it
	 becomes idle)
      3. Find the PID of the process using ps -x
      4. Send a SIGUSR1 signal to the program to cause it to write a
	 new rain.inc file to disk.  The program will automatically update
	 after each signal, so a series of SIGUSR1 signals will force it
	 to step through the simulation.

		kill -USR1 <pid>

Any reasonable questions can be directed to agage@mines.edu
