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flightgear/Astro/moon.c

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Moved from .../Src/Scenery/ to .../Src/Astro/
1998-01-07 03:16:15 +00:00
/**************************************************************************
* moon.c
* Written by Durk Talsma. Started October 1997, for the flight gear project.
*
* 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)
**************************************************************************/
#include <math.h>
#include <GL/glut.h>
#include "../XGL/xgl.h"
#include "orbits.h"
#include "moon.h"
#include "../Aircraft/aircraft.h"
#include "../Include/constants.h"
#include "../Include/general.h"
#include "../Main/views.h"
#include "../Time/fg_time.h"
struct CelestialCoord moonPos;
static float xMoon, yMoon, zMoon;
static GLint moon;
/*
static GLfloat vdata[12][3] =
{
{-X, 0.0, Z }, { X, 0.0, Z }, {-X, 0.0, -Z}, {X, 0.0, -Z },
{ 0.0, Z, X }, { 0.0, Z, -X}, {0.0, -Z, -X}, {0.0, -Z, -X},
{ Z, X, 0.0 }, { -Z, X, 0.0}, {Z, -X, 0.0 }, {-Z, -X, 0.0}
};
static GLuint tindices[20][3] =
{
{0,4,1}, {0,9,4}, {9,5,4}, {4,5,8}, {4,8,1},
{8,10,1}, {8,3,10}, {5,3,8}, {5,2,3}, {2,7,3},
{7,10,3}, {7,6,10}, {7,11,6}, {11,0,6}, {0,1,6},
{6,1,10}, {9,0,11}, {9,11,2}, {9,2,5}, {7,2,11}
};*/
/* -------------------------------------------------------------
This section contains the code that generates a yellow
Icosahedron. It's under development... (of Course)
______________________________________________________________*/
/*
void NormalizeVector(float v[3])
{
GLfloat d = sqrt(v[0] * v[0] + v[1] * v[1] + v[2] * v[2]);
if (d == 0.0)
{
printf("zero length vector\n");
return;
}
v[0] /= d;
v[1] /= d;
v[2] /= d;
}
void drawTriangle(float *v1, float *v2, float *v3)
{
xglBegin(GL_POLYGON);
//xglBegin(GL_POINTS);
xglNormal3fv(v1);
xglVertex3fv(v1);
xglNormal3fv(v2);
xglVertex3fv(v2);
xglNormal3fv(v3);
xglVertex3fv(v3);
xglEnd();
}
void subdivide(float *v1, float *v2, float *v3, long depth)
{
GLfloat v12[3], v23[3], v31[3];
GLint i;
if (!depth)
{
drawTriangle(v1, v2, v3);
return;
}
for (i = 0; i < 3; i++)
{
v12[i] = (v1[i] + v2[i]);
v23[i] = (v2[i] + v3[i]);
v31[i] = (v3[i] + v1[i]);
}
NormalizeVector(v12);
NormalizeVector(v23);
NormalizeVector(v31);
subdivide(v1, v12, v31, depth - 1);
subdivide(v2, v23, v12, depth - 1);
subdivide(v3, v31, v23, depth - 1);
subdivide(v12, v23, v31,depth - 1);
} */
/*
void display(void)
{
int i;
xglClear(GL_COLOR_BUFFER_BIT);
xglPushMatrix();
xglRotatef(spin, 0.0, 0.0, 0.0);
xglColor3f(1.0, 1.0, 0.0);
// xglBegin(GL_LINE_LOOP);
for (i = 0; i < 20; i++)
{
//xglVertex3fv(&vdata[tindices[i][0]][0]);
//xglVertex3fv(&vdata[tindices[i][1]][0]);
//xglVertex3fv(&vdata[tindices[i][2]][0]);
subdivide(&vdata[tindices[i][0]][0],
&vdata[tindices[i][1]][0],
&vdata[tindices[i][2]][0], 3);
}
// xglEnd();
// xglFlush();
xglPopMatrix();
glutSwapBuffers();
} */
/* --------------------------------------------------------------
This section contains the code that calculates the actual
position of the moon in the night sky.
----------------------------------------------------------------*/
struct CelestialCoord fgCalculateMoon(struct OrbElements params,
struct OrbElements sunParams,
struct fgTIME t)
{
struct CelestialCoord
geocCoord, topocCoord;
double
eccAnom, ecl, lonecl, latecl, actTime,
xv, yv, v, r, xh, yh, zh, xg, yg, zg, xe, ye, ze,
Ls, Lm, D, F, mpar, gclat, rho, HA, g;
struct fgAIRCRAFT *a;
struct fgFLIGHT *f;
a = &current_aircraft;
f = &a->flight;
/* calculate the angle between ecliptic and equatorial coordinate system */
actTime = fgCalcActTime(t);
ecl = fgDegToRad(23.4393 - 3.563E-7 * actTime); // in radians of course
/* calculate the eccentric anomaly */
eccAnom = fgCalcEccAnom(params.M, params.e);
/* calculate the moon's distance (d) and true anomaly (v) */
xv = params.a * ( cos(eccAnom) - params.e);
yv = params.a * ( sqrt(1.0 - params.e*params.e) * sin(eccAnom));
v =atan2(yv, xv);
r = sqrt(xv*xv + yv*yv);
/* estimate the geocentric rectangular coordinates here */
xh = r * (cos(params.N) * cos(v + params.w) - sin(params.N) * sin(v + params.w) * cos(params.i));
yh = r * (sin(params.N) * cos(v + params.w) + cos(params.N) * sin(v + params.w) * cos(params.i));
zh = r * (sin(v + params.w) * sin(params.i));
/* calculate the ecliptic latitude and longitude here */
lonecl = atan2( yh, xh);
latecl = atan2( zh, sqrt( xh*xh + yh*yh));
/* calculate a number of perturbations */
Ls = sunParams.M + sunParams.w;
Lm = params.M + params.w + params.N;
D = Lm - Ls;
F = Lm - params.N;
lonecl += fgDegToRad(
- 1.274 * sin (params.M - 2*D) // the Evection
+ 0.658 * sin (2 * D) // the Variation
- 0.186 * sin (sunParams.M) // the yearly variation
- 0.059 * sin (2*params.M - 2*D)
- 0.057 * sin (params.M - 2*D + sunParams.M)
+ 0.053 * sin (params.M + 2*D)
+ 0.046 * sin (2*D - sunParams.M)
+ 0.041 * sin (params.M - sunParams.M)
- 0.035 * sin (D) // the Parallactic Equation
- 0.031 * sin (params.M + sunParams.M)
- 0.015 * sin (2*F - 2*D)
+ 0.011 * sin (params.M - 4*D)
); /* Pheeuuwwww */
latecl += fgDegToRad(
- 0.173 * sin (F - 2*D)
- 0.055 * sin (params.M - F - 2*D)
- 0.046 * sin (params.M + F - 2*D)
+ 0.033 * sin (F + 2*D)
+ 0.017 * sin (2 * params.M + F)
); /* Yep */
r += (
- 0.58 * cos(params.M - 2*D)
- 0.46 * cos(2*D)
); /* Ok! */
xg = r * cos(lonecl) * cos(latecl);
yg = r * sin(lonecl) * cos(latecl);
zg = r * sin(latecl);
xe = xg;
ye = yg * cos(ecl) - zg * sin(ecl);
ze = yg * sin(ecl) + zg * cos(ecl);
geocCoord.RightAscension = atan2(ye, xe);
geocCoord.Declination = atan2(ze, sqrt(xe*xe + ye*ye));
/* New since 25 december 1997 */
/* Calculate the moon's topocentric position instead of it's geocentric! */
mpar = asin( 1 / r); /* calculate the moon's parrallax, i.e. the apparent size of the
(equatorial) radius of the Earth, as seen from the moon */
gclat = FG_Latitude - 0.083358 * sin (2 * fgDegToRad( FG_Latitude));
rho = 0.99883 + 0.00167 * cos(2 * fgDegToRad(FG_Latitude));
if (geocCoord.RightAscension < 0)
geocCoord.RightAscension += (2*FG_PI);
HA = t.lst - (3.8197186 * geocCoord.RightAscension);
g = atan (tan(gclat) / cos( (HA / 3.8197186)));
topocCoord.RightAscension = geocCoord.RightAscension - mpar * rho * cos(gclat) * sin(HA) / cos(geocCoord.Declination);
topocCoord.Declination = geocCoord.Declination - mpar * rho * sin(gclat) * sin(g - geocCoord.Declination) / sin(g);
return topocCoord;
}
void fgMoonInit() {
struct fgLIGHT *l;
static int dl_exists = 0;
printf("Initializing the Moon\n");
l = &cur_light_params;
/* position the moon */
fgSolarSystemUpdate(&(pltOrbElements[1]), cur_time_params);
moonPos = fgCalculateMoon(pltOrbElements[1], pltOrbElements[0],
cur_time_params);
#ifdef DEBUG
printf("Moon found at %f (ra), %f (dec)\n", moonPos.RightAscension,
moonPos.Declination);
#endif
xMoon = 60000.0 * cos(moonPos.RightAscension) * cos(moonPos.Declination);
yMoon = 60000.0 * sin(moonPos.RightAscension) * cos(moonPos.Declination);
zMoon = 60000.0 * sin(moonPos.Declination);
if ( !dl_exists ) {
dl_exists = 1;
/* printf("First time through, creating moon display list\n"); */
moon = xglGenLists(1);
xglNewList(moon, GL_COMPILE );
/* xglMaterialfv(GL_FRONT, GL_AMBIENT, l->scene_clear);
xglMaterialfv(GL_FRONT, GL_DIFFUSE, moon_color); */
glutSolidSphere(1.0, 10, 10);
xglEndList();
}
}
/* Draw the moon */
void fgMoonRender() {
struct fgLIGHT *l;
GLfloat white[4] = { 1.0, 1.0, 1.0, 1.0 };
/* printf("Rendering moon\n"); */
l = &cur_light_params;
xglMaterialfv(GL_FRONT, GL_AMBIENT, l->sky_color );
xglMaterialfv(GL_FRONT, GL_DIFFUSE, white);
xglPushMatrix();
xglTranslatef(xMoon, yMoon, zMoon);
xglScalef(1400, 1400, 1400);
xglCallList(moon);
xglPopMatrix();
}
/* $Log$
/* Revision 1.1 1998/01/07 03:16:16 curt
/* Moved from .../Src/Scenery/ to .../Src/Astro/
/*
* Revision 1.16 1998/01/06 01:20:24 curt
* Tweaks to help building with MSVC++
*
* Revision 1.15 1998/01/05 18:44:35 curt
* Add an option to advance/decrease time from keyboard.
*
* Revision 1.14 1997/12/30 20:47:50 curt
* Integrated new event manager with subsystem initializations.
*
* Revision 1.13 1997/12/30 16:41:00 curt
* Added log at end of file.
*
*/
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