172 lines
5.4 KiB
C
172 lines
5.4 KiB
C
/**************************************************************************
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* moon.c
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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 <math.h>
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#include <GL/glut.h>
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#include "orbits.h"
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#include "moon.h"
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#include "../Time/fg_time.h"
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#include "../GLUT/views.h"
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/* #include "../Aircraft/aircraft.h"*/
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#include "../general.h"
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static GLint moon;
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struct CelestialCoord fgCalculateMoon(struct OrbElements params,
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struct OrbElements sunParams,
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struct fgTIME t)
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{
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struct CelestialCoord
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result;
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double
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eccAnom, ecl, lonecl, latecl, actTime,
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xv, yv, v, r, xh, yh, zh, xg, yg, zg, xe, ye, ze,
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Ls, Lm, D, F;
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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); // in radians of course
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/* calculate the eccentric anomaly */
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eccAnom = fgCalcEccAnom(params.M, params.e);
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/* calculate the moon's distance (d) and true anomaly (v) */
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xv = params.a * ( cos(eccAnom) - params.e);
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yv = params.a * ( 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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/* estimate the geocentric rectangular coordinates here */
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xh = r * (cos(params.N) * cos(v + params.w) - sin(params.N) * sin(v + params.w) * cos(params.i));
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yh = r * (sin(params.N) * cos(v + params.w) + cos(params.N) * sin(v + params.w) * cos(params.i));
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zh = r * (sin(v + params.w) * sin(params.i));
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/* calculate the ecliptic latitude and longitude here */
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lonecl = atan2( yh, xh);
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latecl = atan2( zh, sqrt( xh*xh + yh*yh));
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/* calculate a number of perturbations */
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Ls = sunParams.M + sunParams.w;
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Lm = params.M + params.w + params.N;
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D = Lm - Ls;
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F = Lm - params.N;
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lonecl += fgDegToRad(
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- 1.274 * sin (params.M - 2*D) // the Evection
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+ 0.658 * sin (2 * D) // the Variation
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- 0.186 * sin (sunParams.M) // the yearly variation
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- 0.059 * sin (2*params.M - 2*D)
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- 0.057 * sin (params.M - 2*D + sunParams.M)
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+ 0.053 * sin (params.M + 2*D)
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+ 0.046 * sin (2*D - sunParams.M)
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+ 0.041 * sin (params.M - sunParams.M)
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- 0.035 * sin (D) // the Parallactic Equation
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- 0.031 * sin (params.M + sunParams.M)
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- 0.015 * sin (2*F - 2*D)
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+ 0.011 * sin (params.M - 4*D)
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); /* Pheeuuwwww */
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latecl += fgDegToRad(
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- 0.173 * sin (F - 2*D)
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- 0.055 * sin (params.M - F - 2*D)
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- 0.046 * sin (params.M + F - 2*D)
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+ 0.033 * sin (F + 2*D)
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+ 0.017 * sin (2 * params.M + F)
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); /* Yep */
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r += (
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- 0.58 * cos(params.M - 2*D)
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- 0.46 * cos(2*D)
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);
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xg = r * cos(lonecl) * cos(latecl);
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yg = r * sin(lonecl) * cos(latecl);
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zg = r * sin(latecl);
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xe = xg;
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ye = yg * cos(ecl) - zg * sin(ecl);
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ze = yg * sin(ecl) + zg * cos(ecl);
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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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void fgMoonInit()
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{
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struct CelestialCoord
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moonPos;
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moon = glGenLists(1);
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glNewList(moon, GL_COMPILE );
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glBegin( GL_POINTS );
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moonPos = fgCalculateMoon(pltOrbElements[1], pltOrbElements[0], cur_time_params);
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printf("Moon found at %f (ra), %f (dec)\n", moonPos.RightAscension, moonPos.Declination);
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/* give the moon a temporary color, for testing purposes */
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glColor3f( 0.0, 1.0, 0.0);
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glVertex3f( 190000.0 * cos(moonPos.RightAscension) * cos(moonPos.Declination),
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190000.0 * sin(moonPos.RightAscension) * cos(moonPos.Declination),
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190000.0 * sin(moonPos.Declination) );
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glEnd();
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glEndList();
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}
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void fgMoonRender()
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{
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double angle;
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static double warp = 0;
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struct VIEW *v;
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struct fgTIME *t;
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t = &cur_time_params;
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v = ¤t_view;
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glDisable( GL_FOG );
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glDisable( GL_LIGHTING );
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glPushMatrix();
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glTranslatef( v->view_pos.x, v->view_pos.y, v->view_pos.z );
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angle = t->gst * 15.0; /* 15 degrees per hour rotation */
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/* warp += 1.0; */
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/* warp = 15.0; */
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warp = 0.0;
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glRotatef( (angle+warp), 0.0, 0.0, -1.0 );
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printf("Rotating moon by %.2f degrees + %.2f degrees\n",angle,warp);
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glCallList(moon);
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glPopMatrix();
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glEnable( GL_LIGHTING );
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glEnable( GL_FOG );
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}
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/* $Log$
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/* Revision 1.1 1997/10/25 03:16:08 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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