flightgear/Scenery/sky.c

/**************************************************************************
 * sky.c -- model sky with an upside down "bowl"
 *
 * Written by Curtis Olson, started December 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 WIN32
#  include <windows.h>
#endif

#include <math.h>
/*
#include <stdio.h>
#include <string.h>
#include <time.h>
*/

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

#include "sky.h"

#include "../Time/fg_time.h"

#include "../Aircraft/aircraft.h"
#include "../Flight/flight.h"
#include "../Include/constants.h"
#include "../Main/views.h"
#include "../Math/fg_random.h"
/*
#include "../Include/general.h"
*/

/* in meters of course */
#define CENTER_ELEV   25000.0
#define INNER_RADIUS  50000.0
#define INNER_ELEV    20000.0
#define MIDDLE_RADIUS 70000.0
#define MIDDLE_ELEV    8000.0
#define OUTER_RADIUS  80000.0
#define OUTER_ELEV        0.0


static float inner_vertex[12][3];
static float middle_vertex[12][3];
static float outer_vertex[12][3];

static float inner_color[12][4];
static float middle_color[12][4];
static float outer_color[12][4];


/* Calculate the sky structure vertices */
void fgSkyVerticesInit() {
    float theta;
    int i;

    printf("Generating the sky dome vertices.\n");

    for ( i = 0; i < 12; i++ ) {
	theta = (i * 30.0) * DEG_TO_RAD;
	
	inner_vertex[i][0] = cos(theta) * INNER_RADIUS;
	inner_vertex[i][1] = sin(theta) * INNER_RADIUS;
	inner_vertex[i][2] = INNER_ELEV;
	
	printf(" %.2f %.2f\n", cos(theta) * INNER_RADIUS, 
	       sin(theta) * INNER_RADIUS);

	middle_vertex[i][0] = cos((double)theta) * MIDDLE_RADIUS;
	middle_vertex[i][1] = sin((double)theta) * MIDDLE_RADIUS;
	middle_vertex[i][2] = MIDDLE_ELEV;
	    
	outer_vertex[i][0] = cos((double)theta) * OUTER_RADIUS;
	outer_vertex[i][1] = sin((double)theta) * OUTER_RADIUS;
	outer_vertex[i][2] = OUTER_ELEV;
	    
    }
}


/* (Re)calculate the sky colors at each vertex */
void fgSkyColorsInit() {
    struct fgLIGHT *l;
    float sun_angle, diff;
    float outer_red_param, outer_red_amt, outer_red_diff;
    float middle_red_param, middle_red_amt, middle_red_diff;
    int i, j;

    l = &cur_light_params;

    printf("Generating the sky colors for each vertex.\n");

    /* setup for the possibility of sunset effects */
    sun_angle = l->sun_angle * RAD_TO_DEG;
    printf("  Sun angle in degrees = %.2f\n", sun_angle);

    if ( (sun_angle > 80.0) && (sun_angle < 100.0) ) {
	/* 0.0 - 0.4 */
	outer_red_param = (10.0 - fabs(90.0 - sun_angle)) / 25.0;
	outer_red_diff = outer_red_param / 6.0;
    } else {
	outer_red_param = 0.0;
	outer_red_diff = 0.0;
    }
    printf("  outer_red_param = %.2f  outer_red_diff = %.2f\n", 
	   outer_red_param, outer_red_diff);

    if ( (sun_angle > 85.0) && (sun_angle < 95.0) ) {
	/* 0.0 - 0.4 */
	middle_red_param = (5.0 - fabs(90.0 - sun_angle)) / 12.5;
	middle_red_diff = middle_red_param / 6.0;
    } else {
	middle_red_param = 0.0;
	middle_red_diff = 0.0;
    }
    printf("  middle_red_param = %.2f  middle_red_diff = %.2f\n", 
	   middle_red_param, middle_red_diff);

    /* calculate transition colors between sky and fog */
    outer_red_amt = outer_red_param;
    middle_red_amt = middle_red_param;

    for ( i = 0; i < 6; i++ ) {
	for ( j = 0; j < 3; j++ ) {
	    diff = l->sky_color[j] - l->fog_color[j];
	    inner_color[i][j] = l->sky_color[j] - diff * 0.3;
	    middle_color[i][j] = l->sky_color[j] - diff * 0.9;
	    outer_color[i][j] = l->fog_color[j];
	}
	outer_color[i][0] += outer_red_amt;
	middle_color[i][0] += middle_red_amt;
	if ( outer_color[i][0] > 1.0 ) { outer_color[i][0] = 1.0; }
	if ( middle_color[i][0] > 1.0 ) { middle_color[i][0] = 1.0; }
	inner_color[i][3] = middle_color[i][3] = outer_color[i][3] = 
	    l->sky_color[3];

	outer_red_amt -= outer_red_diff;
	middle_red_amt -= middle_red_diff;

	printf("inner_color[%d] = %.2f %.2f %.2f %.2f\n", i, inner_color[i][0],
	       inner_color[i][1], inner_color[i][2], inner_color[i][3]);
	printf("middle_color[%d] = %.2f %.2f %.2f %.2f\n", i, 
	       middle_color[i][0], middle_color[i][1], middle_color[i][2], 
	       middle_color[i][3]);
	printf("outer_color[%d] = %.2f %.2f %.2f %.2f\n", i, 
	       outer_color[i][0], outer_color[i][1], outer_color[i][2], 
	       outer_color[i][3]);
    }

    outer_red_amt = 0.0;
    middle_red_amt = 0.0;

    for ( i = 6; i < 12; i++ ) {

	for ( j = 0; j < 3; j++ ) {
	    diff = l->sky_color[j] - l->fog_color[j];
	    inner_color[i][j] = l->sky_color[j] - diff * 0.3;
	    middle_color[i][j] = l->sky_color[j] - diff * 0.9;
	    outer_color[i][j] = l->fog_color[j];
	}
	outer_color[i][0] += outer_red_amt;
	middle_color[i][0] += middle_red_amt;
	if ( outer_color[i][0] > 1.0 ) { outer_color[i][0] = 1.0; }
	if ( middle_color[i][0] > 1.0 ) { middle_color[i][0] = 1.0; }
	inner_color[i][3] = middle_color[i][3] = outer_color[i][3] = 
	    l->sky_color[3];

	outer_red_amt += outer_red_diff;
	middle_red_amt += middle_red_diff;

	printf("inner_color[%d] = %.2f %.2f %.2f %.2f\n", i, inner_color[i][0],
	       inner_color[i][1], inner_color[i][2], inner_color[i][3]);
	printf("middle_color[%d] = %.2f %.2f %.2f %.2f\n", i, 
	       middle_color[i][0], middle_color[i][1], middle_color[i][2], 
	       middle_color[i][3]);
	printf("outer_color[%d] = %.2f %.2f %.2f %.2f\n", i, 
	       outer_color[i][0], outer_color[i][1], outer_color[i][2], 
	       outer_color[i][3]);
    }
}


/* Initialize the sky structure and colors */
void fgSkyInit() {
    fgSkyVerticesInit();
    fgSkyColorsInit();
}


/* Draw the Sky */
void fgSkyRender() {
    struct fgFLIGHT *f;
    struct fgLIGHT *l;
    struct fgVIEW *v;
    float /* inner_color[4], middle_color[4], diff, */ east_dot, dot, angle;
    int i;

    f = &current_aircraft.flight;
    l = &cur_light_params;
    v = &current_view;

    printf("Rendering the sky.\n");

    xglPushMatrix();

    /* calculate the angle between v->surface_to_sun and
     * v->surface_east.  We do this so we can sort out the acos()
     * ambiguity.  I wish I could think of a more efficient way ... :-( */
    east_dot = MAT3_DOT_PRODUCT(v->surface_to_sun, v->surface_east);
    printf("  East dot product = %.2f\n", east_dot);

    /* calculate the angle between v->surface_to_sun and
     * v->surface_south.  this is how much we have to rotate the sky
     * for it to align with the sun */
    dot = MAT3_DOT_PRODUCT(v->surface_to_sun, v->surface_south);
    printf("  Dot product = %.2f\n", dot);
    if ( east_dot >= 0 ) {
	angle = acos(dot);
    } else {
	angle = -acos(dot);
    }
    printf("  Sky needs to rotate = %.3f rads = %.1f degrees.\n", 
	   angle, angle * RAD_TO_DEG);

    /* Translate to view position */
    xglTranslatef( v->cur_zero_elev.x, v->cur_zero_elev.y, v->cur_zero_elev.z );
    /* printf("  Translated to %.2f %.2f %.2f\n", 
	   v->cur_zero_elev.x, v->cur_zero_elev.y, v->cur_zero_elev.z ); */

    /* Rotate to proper orientation */
    printf("  lon = %.2f  lat = %.2f\n", FG_Longitude * RAD_TO_DEG,
	   FG_Latitude * RAD_TO_DEG);
    xglRotatef( FG_Longitude * RAD_TO_DEG, 0.0, 0.0, 1.0 );
    xglRotatef( 90.0 - FG_Latitude * RAD_TO_DEG, 0.0, 1.0, 0.0 );
    xglRotatef( angle * RAD_TO_DEG, 0.0, 0.0, 1.0 );

    /* Draw inner/center section of sky*/
    xglBegin( GL_TRIANGLE_FAN );
    xglColor4fv(l->sky_color);
    xglVertex3f(0.0, 0.0, CENTER_ELEV);
    for ( i = 0; i < 12; i++ ) {
	xglColor4fv( inner_color[i] );
	xglVertex3fv( inner_vertex[i] );
    }
    xglColor4fv( inner_color[0] );
    xglVertex3fv( inner_vertex[0] );
    xglEnd();

    /* Draw the middle ring */
    xglBegin( GL_TRIANGLE_STRIP );
    for ( i = 0; i < 12; i++ ) {
	xglColor4fv( middle_color[i] );
	xglVertex3fv( middle_vertex[i] );
	xglColor4fv( inner_color[i] );
	xglVertex3fv( inner_vertex[i] );
    }
    xglColor4fv( middle_color[0] );
    /* xglColor4f(1.0, 0.0, 0.0, 1.0); */
    xglVertex3fv( middle_vertex[0] );
    xglColor4fv( inner_color[0] );
    /* xglColor4f(1.0, 0.0, 0.0, 1.0); */
    xglVertex3fv( inner_vertex[0] );
    xglEnd();

    /* Draw the outer ring */
    xglBegin( GL_TRIANGLE_STRIP );
    for ( i = 0; i < 12; i++ ) {
	xglColor4fv( outer_color[i] );
	xglVertex3fv( outer_vertex[i] );
	xglColor4fv( middle_color[i] );
	xglVertex3fv( middle_vertex[i] );
    }
    xglColor4fv( outer_color[0] );
    xglVertex3fv( outer_vertex[0] );
    xglColor4fv( middle_color[0] );
    xglVertex3fv( middle_vertex[0] );
    xglEnd();

    xglPopMatrix();
}


/* $Log$
/* Revision 1.7  1997/12/22 23:45:48  curt
/* First stab at sunset/sunrise sky glow effects.
/*
 * Revision 1.6  1997/12/22 04:14:34  curt
 * Aligned sky with sun so dusk/dawn effects can be correct relative to the sun.
 *
 * Revision 1.5  1997/12/19 23:34:59  curt
 * Lot's of tweaking with sky rendering and lighting.
 *
 * Revision 1.4  1997/12/19 16:45:02  curt
 * Working on scene rendering order and options.
 *
 * Revision 1.3  1997/12/18 23:32:36  curt
 * First stab at sky dome actually starting to look reasonable. :-)
 *
 * Revision 1.2  1997/12/18 04:07:03  curt
 * Worked on properly translating and positioning the sky dome.
 *
 * Revision 1.1  1997/12/17 23:14:30  curt
 * Initial revision.
 * Begin work on rendering the sky. (Rather than just using a clear screen.)
 *
 */