237 lines
6.5 KiB
C
237 lines
6.5 KiB
C
/**************************************************************************
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* sun.c
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*
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* Written 1997 by Durk Talsma, started October, 1997. For the flight gear
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* project.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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* $Id$
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* (Log is kept at end of this file)
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**************************************************************************/
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#include <GL/glut.h>
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#include "../XGL/xgl.h"
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#include "../Time/fg_time.h"
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#include "../Main/views.h"
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#include "orbits.h"
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#include "sun.h"
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GLint sun_obj;
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static struct CelestialCoord sunPos;
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float xSun, ySun, zSun;
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struct SunPos fgCalcSunPos(struct OrbElements params)
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{
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double
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EccAnom, lonSun,
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xv, yv, v, r;
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struct SunPos
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solarPosition;
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/* calculate the eccentric anomaly */
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EccAnom = fgCalcEccAnom(params.M, params.e);
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/* calculate the Suns distance (r) and its true anomaly (v) */
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xv = cos(EccAnom) - params.e;
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yv = sqrt(1.0 - params.e*params.e) * sin(EccAnom);
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v = atan2(yv, xv);
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r = sqrt(xv*xv + yv*yv);
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/* calculate the the Sun's true longitude (lonsun) */
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lonSun = v + params.w;
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/* convert true longitude and distance to ecliptic rectangular geocentric
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coordinates (xs, ys) */
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solarPosition.xs = r * cos(lonSun);
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solarPosition.ys = r * sin(lonSun);
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solarPosition.dist = r;
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return solarPosition;
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}
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struct CelestialCoord fgCalculateSun(struct OrbElements params, struct fgTIME t)
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{
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struct CelestialCoord
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result;
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struct SunPos
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SolarPosition;
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double
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xe, ye, ze, ecl, actTime;
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/* calculate the angle between ecliptic and equatorial coordinate system */
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actTime = fgCalcActTime(t);
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ecl = fgDegToRad(23.4393 - 3.563E-7 * actTime); // Angle now in Rads
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/* calculate the sun's ecliptic position */
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SolarPosition = fgCalcSunPos(params);
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/* convert ecliptic coordinates to equatorial rectangular geocentric coordinates */
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xe = SolarPosition.xs;
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ye = SolarPosition.ys * cos(ecl);
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ze = SolarPosition.ys * sin(ecl);
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/* and finally... Calulate Right Ascention and Declination */
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result.RightAscension = atan2( ye, xe);
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result.Declination = atan2(ze, sqrt(xe*xe + ye*ye));
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return result;
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}
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/* Initialize the Sun */
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void fgSunInit() {
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static int dl_exists = 0;
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printf(" Initializing the Sun\n");
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fgSolarSystemUpdate(&(pltOrbElements[0]), cur_time_params);
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sunPos = fgCalculateSun(pltOrbElements[0], cur_time_params);
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#ifdef DEBUG
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printf("Sun found at %f (ra), %f (dec)\n", sunPos.RightAscension,
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sunPos.Declination);
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#endif
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xSun = 60000.0 * cos(sunPos.RightAscension) * cos(sunPos.Declination);
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ySun = 60000.0 * sin(sunPos.RightAscension) * cos(sunPos.Declination);
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zSun = 60000.0 * sin(sunPos.Declination);
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if ( !dl_exists ) {
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dl_exists = 1;
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/* printf("First time through, creating sun display list\n"); */
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sun_obj = xglGenLists(1);
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xglNewList(sun_obj, GL_COMPILE );
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glutSolidSphere(1.0, 10, 10);
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xglEndList();
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}
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}
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/* Draw the Sun */
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void fgSunRender() {
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struct fgVIEW *v;
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struct fgTIME *t;
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struct fgLIGHT *l;
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/* GLfloat color[4] = { 0.85, 0.65, 0.05, 1.0 }; */
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GLfloat color[4] = { 1.00, 1.00, 1.00, 1.00 };
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double x_2, x_4, x_8, x_10;
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GLfloat ambient;
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GLfloat amb[3], diff[3];
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t = &cur_time_params;
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v = ¤t_view;
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l = &cur_light_params;
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x_2 = l->sun_angle * l->sun_angle;
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x_4 = x_2 * x_2;
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x_8 = x_4 * x_4;
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x_10 = x_8 * x_2;
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ambient = (0.4 * pow(1.1, -x_10 / 30.0));
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if ( ambient < 0.3 ) ambient = 0.3;
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if ( ambient > 1.0 ) ambient = 1.0;
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amb[0] = 0.50 + ((ambient * 6.66) - 1.6);
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amb[1] = 0.00 + ((ambient * 6.66) - 1.6);
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amb[2] = 0.00 + ((ambient * 6.66) - 1.6);
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amb[3] = 0.00;
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#ifdef DEBUG
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printf("Color of the sun: %f, %f, %f\n"
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"Ambient value : %f\n"
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"Sun Angle : %f\n" , amb[0], amb[1], amb[2], ambient, t->sun_angle);
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#endif
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diff[0] = 0.0;
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diff[1] = 0.0;
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diff[2] = 0.0;
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diff[3] = 1.0;
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/* set lighting parameters */
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xglLightfv(GL_LIGHT0, GL_AMBIENT, color );
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xglLightfv(GL_LIGHT0, GL_DIFFUSE, color );
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xglMaterialfv(GL_FRONT, GL_AMBIENT, amb);
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xglMaterialfv(GL_FRONT, GL_DIFFUSE, diff);
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xglMaterialfv(GL_FRONT, GL_SHININESS, diff);
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xglMaterialfv(GL_FRONT, GL_EMISSION, diff);
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xglMaterialfv(GL_FRONT, GL_SPECULAR, diff);
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/* xglDisable( GL_LIGHTING ); */
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xglPushMatrix();
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xglTranslatef(xSun, ySun, zSun);
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xglScalef(1400, 1400, 1400);
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xglColor3f(0.85, 0.65, 0.05);
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xglCallList(sun_obj);
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xglPopMatrix();
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/* xglEnable( GL_LIGHTING ); */
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}
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/* $Log$
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/* Revision 1.12 1998/01/05 18:44:36 curt
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/* Add an option to advance/decrease time from keyboard.
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/*
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* Revision 1.11 1997/12/30 23:09:40 curt
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* Worked on winding problem without luck, so back to calling glFrontFace()
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* 3 times for each scenery area.
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*
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* Revision 1.10 1997/12/30 20:47:54 curt
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* Integrated new event manager with subsystem initializations.
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*
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* Revision 1.9 1997/12/30 16:36:54 curt
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* Merged in Durk's changes ...
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*
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* Revision 1.8 1997/12/19 23:35:00 curt
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* Lot's of tweaking with sky rendering and lighting.
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*
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* Revision 1.7 1997/12/17 23:12:16 curt
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* Fixed so moon and sun display lists aren't recreate periodically.
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*
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* Revision 1.6 1997/12/15 23:55:04 curt
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* Add xgl wrappers for debugging.
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* Generate terrain normals on the fly.
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*
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* Revision 1.5 1997/12/12 21:41:31 curt
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* More light/material property tweaking ... still a ways off.
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*
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* Revision 1.4 1997/12/10 22:37:53 curt
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* Prepended "fg" on the name of all global structures that didn't have it yet.
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* i.e. "struct WEATHER {}" became "struct fgWEATHER {}"
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*
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* Revision 1.3 1997/12/09 05:11:56 curt
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* Working on tweaking lighting.
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*
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* Revision 1.2 1997/11/25 19:25:39 curt
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* Changes to integrate Durk's moon/sun code updates + clean up.
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*
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* Revision 1.1 1997/10/25 03:16:11 curt
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* Initial revision of code contributed by Durk Talsma.
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*
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*/
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