230 lines
7.4 KiB
C++
230 lines
7.4 KiB
C++
/**************************************************************************
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* moon.cxx
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* Written by Durk Talsma. Originally started October 1997, for distribution
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* with the FlightGear project. Version 2 was written in August and
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* September 1998. This code is based upon algorithms and data kindly
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* provided by Mr. Paul Schlyter. (pausch@saaf.se).
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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 <Flight/flight.hxx>
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#include <string.h>
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#include "moon.hxx"
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#include <Debug/fg_debug.h>
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#include <Objects/texload.h>
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static GLuint moon_texid;
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static GLubyte *moon_texbuf;
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/*************************************************************************
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* Moon::Moon(fgTIME *t)
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* Public constructor for class Moon. Initializes the orbital elements and
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* sets up the moon texture.
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* Argument: The current time.
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* the hard coded orbital elements for Moon are passed to
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* CelestialBody::CelestialBody();
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************************************************************************/
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Moon::Moon(fgTIME *t) :
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CelestialBody(125.1228, -0.0529538083,
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5.1454, 0.00000,
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318.0634, 0.1643573223,
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60.266600, 0.000000,
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0.054900, 0.000000,
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115.3654, 13.0649929509, t)
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{
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string tpath, fg_tpath;
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int width, height;
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fgPrintf( FG_GENERAL, FG_INFO, "Initializing Moon Texture\n");
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#ifdef GL_VERSION_1_1
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xglGenTextures(1, &moon_texid);
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xglBindTexture(GL_TEXTURE_2D, moon_texid);
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#elif GL_EXT_texture_object
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xglGenTexturesEXT(1, &moon_texid);
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xglBindTextureEXT(GL_TEXTURE_2D, moon_texid);
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#else
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# error port me
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#endif
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glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
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glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
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glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
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// load in the texture data
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tpath = current_options.get_fg_root() + "/Textures/" + "moon.rgb";
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if ( (moon_texbuf = read_rgb_texture(tpath.c_str(), &width, &height))
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== NULL )
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{
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// Try compressed
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fg_tpath = tpath + ".gz";
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if ( (moon_texbuf = read_rgb_texture(fg_tpath.c_str(), &width, &height))
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== NULL )
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{
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fgPrintf( FG_GENERAL, FG_EXIT,
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"Error in loading moon texture %s\n", tpath.c_str() );
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exit(1);
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}
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}
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glTexImage2D( GL_TEXTURE_2D,
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0,
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GL_RGB,
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256, 256,
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0,
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GL_RGB, GL_UNSIGNED_BYTE,
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moon_texbuf);
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}
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/*****************************************************************************
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* void Moon::updatePosition(fgTIME *t, Star *ourSun)
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* this member function calculates the actual topocentric position (i.e.)
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* the position of the moon as seen from the current position on the surface
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* of the moon.
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****************************************************************************/
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void Moon::updatePosition(fgTIME *t, Star *ourSun)
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{
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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, mpar, gclat, rho, HA, g,
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geoRa, geoDec;
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fgAIRCRAFT *air;
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fgFLIGHT *f;
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air = ¤t_aircraft;
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f = air->flight;
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updateOrbElements(t);
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actTime = fgCalcActTime(t);
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// calculate the angle between ecliptic and equatorial coordinate system
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// in Radians
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ecl = ((DEG_TO_RAD * 23.4393) - (DEG_TO_RAD * 3.563E-7) * actTime);
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eccAnom = fgCalcEccAnom(M, e); // Calculate the eccentric anomaly
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xv = a * (cos(eccAnom) - e);
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yv = a * (sqrt(1.0 - e*e) * sin(eccAnom));
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v = atan2(yv, xv); // the moon's true anomaly
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r = sqrt (xv*xv + yv*yv); // and its distance
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// estimate the geocentric rectangular coordinates here
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xh = r * (cos(N) * cos (v+w) - sin (N) * sin(v+w) * cos(i));
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yh = r * (sin(N) * cos (v+w) + cos (N) * sin(v+w) * cos(i));
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zh = r * (sin(v+w) * sin(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 perturbatioin, i.e. disturbances caused by the
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* gravitational infuence of the sun and the other major planets.
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* The largest of these even have a name */
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Ls = ourSun->getM() + ourSun->getw();
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Lm = M + w + N;
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D = Lm - Ls;
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F = Lm - N;
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lonecl += DEG_TO_RAD * (-1.274 * sin (M - 2*D)
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+0.658 * sin (2*D)
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-0.186 * sin(ourSun->getM())
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-0.059 * sin(2*M - 2*D)
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-0.057 * sin(M - 2*D + ourSun->getM())
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+0.053 * sin(M + 2*D)
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+0.046 * sin(2*D - ourSun->getM())
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+0.041 * sin(M - ourSun->getM())
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-0.035 * sin(D)
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-0.031 * sin(M + ourSun->getM())
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-0.015 * sin(2*F - 2*D)
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+0.011 * sin(M - 4*D)
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);
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latecl += DEG_TO_RAD * (-0.173 * sin(F-2*D)
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-0.055 * sin(M - F - 2*D)
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-0.046 * sin(M + F - 2*D)
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+0.033 * sin(F + 2*D)
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+0.017 * sin(2*M + F)
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);
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r += (-0.58 * cos(M - 2*D)
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-0.46 * cos(2*D)
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);
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fgPrintf(FG_GENERAL, FG_INFO, "Running moon update\n");
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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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geoRa = atan2(ye, xe);
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geoDec = atan2(ze, sqrt(xe*xe + ye*ye));
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// Given the moon's geocentric ra and dec, calculate its
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// topocentric ra and dec. i.e. the position as seen from the
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// surface of the earth, instead of the center of the earth
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// First calculates the moon's parrallax, that is, the apparent size of the
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// (equatorial) radius of the earth, as seen from the moon
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mpar = asin ( 1 / r);
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gclat = FG_Latitude - 0.003358 * sin (2 * DEG_TO_RAD * FG_Latitude);
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rho = 0.99883 + 0.00167 * cos(2 * DEG_TO_RAD * FG_Latitude);
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if (geoRa < 0)
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geoRa += (2*FG_PI);
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HA = t->lst - (3.8197186 * geoRa);
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g = atan (tan(gclat) / cos ((HA / 3.8197186)));
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rightAscension = geoRa - mpar * rho * cos(gclat) * sin(HA) / cos (geoDec);
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declination = geoDec - mpar * rho * sin (gclat) * sin (g - geoDec) / sin(g);
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}
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/************************************************************************
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* void Moon::newImage(float ra, float dec)
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*
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* This function regenerates a new visual image of the moon, which is added to
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* solarSystem display list.
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*
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* Arguments: Right Ascension and declination
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*
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* return value: none
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**************************************************************************/
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void Moon::newImage(float ra, float dec)
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{
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glEnable(GL_TEXTURE_2D);
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glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
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glBindTexture(GL_TEXTURE_2D, moon_texid);
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//xglRotatef(-90, 0.0, 0.0, 1.0);
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xglRotatef(((RAD_TO_DEG * ra)- 90.0), 0.0, 0.0, 1.0);
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xglRotatef((RAD_TO_DEG * dec), 1.0, 0.0, 0.0);
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fgPrintf( FG_GENERAL, FG_INFO,
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"Ra = (%f), Dec= (%f)", (RAD_TO_DEG *ra), (RAD_TO_DEG *dec) );
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xglTranslatef(0.0, 58600.0, 0.0);
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Object = gluNewQuadric();
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gluQuadricTexture( Object, GL_TRUE );
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gluSphere( Object, 1367, 12, 12 );
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glDisable(GL_TEXTURE_2D);
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}
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