/**************************************************************************
 * weather.c -- routines to model weather
 *
 * Written by Curtis Olson, started July 1997.
 *
 * Copyright (C) 1997  Curtis L. Olson  - curt@infoplane.com
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 * $Id$
 * (Log is kept at end of this file)
 **************************************************************************/


#ifdef HAVE_CONFIG_H
#  include <config.h>
#endif

#ifdef HAVE_WINDOWS_H
#  include <windows.h>                     
#endif

#include <GL/glut.h>
#include <XGL/xgl.h>

#include <math.h>
#include <stdio.h>

#include <Aircraft/aircraft.h>
#include <Debug/fg_debug.h>
#include <Math/fg_random.h>
#include <Weather/weather.h>


/* This is a record containing current weather info */
struct fgWEATHER current_weather;


/* Initialize the weather modeling subsystem */
void fgWeatherInit( void ) {
    struct fgWEATHER *w;

    w = &current_weather;

    printf("Initializing weather subsystem\n");

    /* Configure some wind */
    /* FG_V_north_airmass = 15; */ /* ft/s =~ 10mph */

    fgWeatherSetVisibility(45000.0);    /* in meters */
}


/* Update the weather parameters for the current position */
void fgWeatherUpdate( void ) {

    /* temporarily remove the code of this do-nothing routine */

#ifdef FG_WEATHER_UPDATE
    fgFLIGHT *f;
    struct fgWEATHER *w;

    f = current_aircraft.flight;
    w = &current_weather;

    /* Add some random turbulence */
    /* FG_U_gust = fg_random() * 1.0 - 0.5;
    FG_V_gust = fg_random() * 1.0 - 0.5;
    FG_W_gust = fg_random() * 1.0 - 0.5; */
#endif FG_WEATHER_UPDATE
}


/* Get the current visibility */
float fgWeatherGetVisibility( void ) {
    struct fgWEATHER *w;
    w = &current_weather;

    return ( w->visibility );
}


/* Set the visibility and update fog parameters */
void fgWeatherSetVisibility( float visibility ) {
    struct fgWEATHER *w;
    w = &current_weather;

    w->visibility = visibility;       /* in meters */
    // w->fog_density = -log(0.01 / w->visibility;        /* for GL_FOG_EXP */
    w->fog_density = sqrt( -log(0.01) ) / w->visibility;  /* for GL_FOG_EXP2 */
    xglFogf (GL_FOG_DENSITY, w->fog_density);
    fgPrintf( FG_INPUT, FG_DEBUG, 
	      "Fog density = %.4f\n", w->fog_density);
}


/* $Log$
/* Revision 1.16  1998/06/12 01:00:59  curt
/* Build only static libraries.
/* Declare memmove/memset for Sloaris.
/* Added support for exponetial fog, which solves for the proper density to
/* achieve the desired visibility range.
/*
 * Revision 1.15  1998/04/25 22:06:34  curt
 * Edited cvs log messages in source files ... bad bad bad!
 *
 * Revision 1.14  1998/02/09 15:07:54  curt
 * Minor tweaks.
 *
 * Revision 1.13  1998/01/27 00:48:08  curt
 * Incorporated Paul Bleisch's <pbleisch@acm.org> new debug message
 * system and commandline/config file processing code.
 *
 * Revision 1.12  1998/01/19 19:27:22  curt
 * Merged in make system changes from Bob Kuehne <rpk@sgi.com>
 * This should simplify things tremendously.
 *
 * Revision 1.11  1998/01/19 18:40:41  curt
 * Tons of little changes to clean up the code and to remove fatal errors
 * when building with the c++ compiler.
 *
 * Revision 1.10  1997/12/30 22:22:46  curt
 * Further integration of event manager.
 *
 * Revision 1.9  1997/12/30 20:48:03  curt
 * Integrated new event manager with subsystem initializations.
 *
 * Revision 1.8  1997/12/11 04:43:58  curt
 * Fixed sun vector and lighting problems.  I thing the moon is now lit
 * correctly.
 *
 * Revision 1.7  1997/12/10 22:37:56  curt
 * Prepended "fg" on the name of all global structures that didn't have it yet.
 * i.e. "struct WEATHER {}" became "struct fgWEATHER {}"
 *
 * Revision 1.6  1997/08/27 03:30:38  curt
 * Changed naming scheme of basic shared structures.
 *
 * Revision 1.5  1997/08/22 21:34:42  curt
 * Doing a bit of reorganizing and house cleaning.
 *
 * Revision 1.4  1997/08/02 16:23:55  curt
 * Misc. tweaks.
 *
 * Revision 1.3  1997/07/31 22:52:41  curt
 * Working on redoing internal coordinate systems & scenery transformations.
 *
 * Revision 1.2  1997/07/30 16:12:44  curt
 * Moved fg_random routines from Util/ to Math/
 *
 * Revision 1.1  1997/07/19 23:03:57  curt
 * Initial revision.
 *
 */