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Eatdirt: Implement parallax effects for the Moon at the rendering stage and not with the ephemeris.

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This commit is contained in:
Erik Hofman 2020-12-30 11:13:42 +01:00
parent 60f5df2998
commit 62501e5ede
9 changed files with 267 additions and 57 deletions
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3
simgear/ephemeris/ephemeris.cxx
View File

@ -68,7 +68,8 @@ SGEphemeris::~SGEphemeris( void ) {
void SGEphemeris::update( double mjd, double lst, double lat ) {
// update object positions
our_sun->updatePosition( mjd );
moon->updatePosition( mjd, lst, lat, our_sun );
// moon->updatePositionTopo( mjd, lst, lat, our_sun );
moon->updatePosition( mjd, our_sun );
mercury->updatePosition( mjd, our_sun );
venus->updatePosition( mjd, our_sun );
mars->updatePosition( mjd, our_sun );

7
simgear/ephemeris/ephemeris.hxx
View File

@ -51,7 +51,7 @@
* Written by Durk Talsma <d.talsma@direct.a2000.nl> and Curtis Olson
* <http://www.flightgear.org/~curt>
*
* Introduction
* Introduction
*
* The SGEphemeris class computes and stores the positions of the Sun,
* the Moon, the planets, and the brightest stars. These positions
@ -146,6 +146,11 @@ public:
return moon->getDeclination();
}
/** @return the geocentric distance to the Moon in unit of its semi-mayor axis. */
inline double getMoonDistanceInMayorAxis() const {
return moon->getDistanceInMayorAxis();
}
/** @return the numbers of defined planets. */
inline int getNumPlanets() const { return nplanets; }

189
simgear/ephemeris/moonpos.cxx
View File

@ -1,9 +1,9 @@
/**************************************************************************
* moonpos.cxx
* Written by Durk Talsma. Originally started October 1997, for distribution
* with the FlightGear project. Version 2 was written in August and
* September 1998. This code is based upon algorithms and data kindly
* provided by Mr. Paul Schlyter. (pausch@saaf.se).
* Written by Durk Talsma. Originally started October 1997, for distribution
* with the FlightGear project. Version 2 was written in August and
* September 1998. This code is based upon algorithms and data kindly
* provided by Mr. Paul Schlyter. (pausch@saaf.se).
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
@ -37,10 +37,10 @@
/*************************************************************************
* MoonPos::MoonPos(double mjd)
* Public constructor for class MoonPos. Initializes the orbital elements and
* Public constructor for class MoonPos. Initializes the orbital elements and
* sets up the moon texture.
* Argument: The current time.
* the hard coded orbital elements for MoonPos are passed to
* the hard coded orbital elements for MoonPos are passed to
* CelestialBody::CelestialBody();
************************************************************************/
MoonPos::MoonPos(double mjd) :
@ -70,21 +70,23 @@ MoonPos::~MoonPos()
/*****************************************************************************
* void MoonPos::updatePosition(double mjd, Star *ourSun)
* this member function calculates the actual topocentric position (i.e.)
* the position of the moon as seen from the current position on the surface
* of the moon.
* void MoonPos::updatePositionTopo(double mjd, double lst, double
* lat, Star *ourSun) this member function calculates the actual
* topocentric position (i.e.) the position of the moon as seen from
* the current position on the surface of the earth. This include
* parallax effects, the moon appears on different stars background
* for different observers on the surface of the earth.
****************************************************************************/
void MoonPos::updatePosition(double mjd, double lst, double lat, Star *ourSun)
void MoonPos::updatePositionTopo(double mjd, double lst, double lat, Star *ourSun)
{
double
double
eccAnom, ecl, actTime,
xv, yv, v, r, xh, yh, zh, zg, xe,
Ls, Lm, D, F, mpar, gclat, rho, HA, g,
geoRa, geoDec,
cosN, sinN, cosvw, sinvw, sinvw_cosi, cosecl, sinecl, rcoslatEcl,
FlesstwoD, MlesstwoD, twoD, twoM, twolat, alpha;
double max_loglux = -0.504030345621;
double min_loglux = -4.39964634562;
double conv = 1.0319696543787917; // The log foot-candle to log lux conversion factor.
@ -99,7 +101,7 @@ void MoonPos::updatePosition(double mjd, double lst, double lat, Star *ourSun)
yv = a * (sqrt(1.0 - e*e) * sin(eccAnom));
v = atan2(yv, xv); // the moon's true anomaly
r = sqrt (xv*xv + yv*yv); // and its distance
// repetitive calculations, minimised for speed
cosN = cos(N);
sinN = sin(N);
@ -118,7 +120,7 @@ void MoonPos::updatePosition(double mjd, double lst, double lat, Star *ourSun)
lonEcl = atan2 (yh, xh);
latEcl = atan2(zh, sqrt(xh*xh + yh*yh));
/* Calculate a number of perturbation, i.e. disturbances caused by the
/* Calculate a number of perturbation, i.e. disturbances caused by the
* gravitational influence of the sun and the other major planets.
* The largest of these even have a name */
Ls = ourSun->getM() + ourSun->getw();
@ -130,7 +132,7 @@ void MoonPos::updatePosition(double mjd, double lst, double lat, Star *ourSun)
twoM = 2 * M;
FlesstwoD = F - twoD;
MlesstwoD = M - twoD;
lonEcl += SGD_DEGREES_TO_RADIANS * (-1.274 * sin(MlesstwoD)
+0.658 * sin(twoD)
-0.186 * sin(ourSun->getM())
@ -154,12 +156,13 @@ void MoonPos::updatePosition(double mjd, double lst, double lat, Star *ourSun)
-0.46 * cos(twoD)
);
distance = r;
distance_in_a = r/a;
// SG_LOG(SG_GENERAL, SG_INFO, "Running moon update");
rcoslatEcl = r * cos(latEcl);
xg = cos(lonEcl) * rcoslatEcl;
yg = sin(lonEcl) * rcoslatEcl;
zg = r * sin(latEcl);
xe = xg;
ye = yg * cosecl -zg * sinecl;
ze = yg * sinecl +zg * cosecl;
@ -167,17 +170,17 @@ void MoonPos::updatePosition(double mjd, double lst, double lat, Star *ourSun)
geoRa = atan2(ye, xe);
geoDec = atan2(ze, sqrt(xe*xe + ye*ye));
/* SG_LOG( SG_GENERAL, SG_INFO,
"(geocentric) geoRa = (" << (SGD_RADIANS_TO_DEGREES * geoRa)
/* SG_LOG( SG_GENERAL, SG_INFO,
"(geocentric) geoRa = (" << (SGD_RADIANS_TO_DEGREES * geoRa)
<< "), geoDec= (" << (SGD_RADIANS_TO_DEGREES * geoDec) << ")" ); */
// Given the moon's geocentric ra and dec, calculate its
// Given the moon's geocentric ra and dec, calculate its
// topocentric ra and dec. i.e. the position as seen from the
// surface of the earth, instead of the center of the earth
// First calculate the moon's parallax, that is, the apparent size of the
// (equatorial) radius of the earth, as seen from the moon
// First calculate the moon's parallax, that is, the apparent size of the
// (equatorial) radius of the earth, as seen from the moon
mpar = asin ( 1 / r);
// SG_LOG( SG_GENERAL, SG_INFO, "r = " << r << " mpar = " << mpar );
// SG_LOG( SG_GENERAL, SG_INFO, "lat = " << f->get_Latitude() );
@ -188,12 +191,12 @@ void MoonPos::updatePosition(double mjd, double lst, double lat, Star *ourSun)
rho = 0.99883 + 0.00167 * cos(twolat);
// SG_LOG( SG_GENERAL, SG_INFO, "rho = " << rho );
if (geoRa < 0)
geoRa += SGD_2PI;
HA = lst - (3.8197186 * geoRa);
/* SG_LOG( SG_GENERAL, SG_INFO, "t->getLst() = " << t->getLst()
/* SG_LOG( SG_GENERAL, SG_INFO, "t->getLst() = " << t->getLst()
<< " HA = " << HA ); */
g = atan (tan(gclat) / cos ((HA / 3.8197186)));
@ -212,8 +215,140 @@ void MoonPos::updatePosition(double mjd, double lst, double lat, Star *ourSun)
// << SGD_RADIANS_TO_DEGREES * (geoDec - declination) << endl;
}
/* SG_LOG( SG_GENERAL, SG_INFO,
"Ra = (" << (SGD_RADIANS_TO_DEGREES *rightAscension)
/* SG_LOG( SG_GENERAL, SG_INFO,
"Ra = (" << (SGD_RADIANS_TO_DEGREES *rightAscension)
<< "), Dec= (" << (SGD_RADIANS_TO_DEGREES *declination) << ")" ); */
// Moon age and phase calculation
age = lonEcl - ourSun->getlonEcl();
phase = (1 - cos(age)) / 2;
// The log of the illuminance of the moon outside the atmosphere.
// This is the base 10 log of equation 20 from Krisciunas K. and Schaefer B.E.
// (1991). A model of the brightness of moonlight, Publ. Astron. Soc. Pacif.
// 103(667), 1033-1039 (DOI: http://dx.doi.org/10.1086/132921).
alpha = SGD_RADIANS_TO_DEGREES * SGMiscd::normalizeAngle(age + SGMiscd::pi());
log_I = -0.4 * (3.84 + 0.026*fabs(alpha) + 4e-9*pow(alpha, 4.0));
// Convert from foot-candles to lux.
log_I += conv;
// The moon's illuminance factor, bracketed between 0 and 1.
I_factor = (log_I - max_loglux) / (max_loglux - min_loglux) + 1.0;
I_factor = SGMiscd::clip(I_factor, 0, 1);
}
/*****************************************************************************
* void MoonPos::updatePosition(double mjd, Star *ourSun) this member
* function calculates the geocentric position (i.e.) the position of
* the moon as seen from the center of earth. As such, it does not
* include any parallax effects. These are taken into account during
* the rendering.
****************************************************************************/
void MoonPos::updatePosition(double mjd, Star *ourSun)
{
double
eccAnom, ecl, actTime,
xv, yv, v, r, xh, yh, zh, zg, xe,
Ls, Lm, D, F, geoRa, geoDec,
cosN, sinN, cosvw, sinvw, sinvw_cosi, cosecl, sinecl, rcoslatEcl,
FlesstwoD, MlesstwoD, twoD, twoM, twolat, alpha;
double max_loglux = -0.504030345621;
double min_loglux = -4.39964634562;
double conv = 1.0319696543787917; // The log foot-candle to log lux conversion factor.
updateOrbElements(mjd);
actTime = sgCalcActTime(mjd);
// calculate the angle between ecliptic and equatorial coordinate system
// in Radians
ecl = SGD_DEGREES_TO_RADIANS * (23.4393 - 3.563E-7 * actTime);
eccAnom = sgCalcEccAnom(M, e); // Calculate the eccentric anomaly
xv = a * (cos(eccAnom) - e);
yv = a * (sqrt(1.0 - e*e) * sin(eccAnom));
v = atan2(yv, xv); // the moon's true anomaly
r = sqrt (xv*xv + yv*yv); // and its distance
// repetitive calculations, minimised for speed
cosN = cos(N);
sinN = sin(N);
cosvw = cos(v+w);
sinvw = sin(v+w);
sinvw_cosi = sinvw * cos(i);
cosecl = cos(ecl);
sinecl = sin(ecl);
// estimate the geocentric rectangular coordinates here
xh = r * (cosN * cosvw - sinN * sinvw_cosi);
yh = r * (sinN * cosvw + cosN * sinvw_cosi);
zh = r * (sinvw * sin(i));
// calculate the ecliptic latitude and longitude here
lonEcl = atan2 (yh, xh);
latEcl = atan2(zh, sqrt(xh*xh + yh*yh));
/* Calculate a number of perturbation, i.e. disturbances caused by the
* gravitational influence of the sun and the other major planets.
* The largest of these even have a name */
Ls = ourSun->getM() + ourSun->getw();
Lm = M + w + N;
D = Lm - Ls;
F = Lm - N;
twoD = 2 * D;
twoM = 2 * M;
FlesstwoD = F - twoD;
MlesstwoD = M - twoD;
lonEcl += SGD_DEGREES_TO_RADIANS * (-1.274 * sin(MlesstwoD)
+0.658 * sin(twoD)
-0.186 * sin(ourSun->getM())
-0.059 * sin(twoM - twoD)
-0.057 * sin(MlesstwoD + ourSun->getM())
+0.053 * sin(M + twoD)
+0.046 * sin(twoD - ourSun->getM())
+0.041 * sin(M - ourSun->getM())
-0.035 * sin(D)
-0.031 * sin(M + ourSun->getM())
-0.015 * sin(2*F - twoD)
+0.011 * sin(M - 4*D)
);
latEcl += SGD_DEGREES_TO_RADIANS * (-0.173 * sin(FlesstwoD)
-0.055 * sin(M - FlesstwoD)
-0.046 * sin(M + FlesstwoD)
+0.033 * sin(F + twoD)
+0.017 * sin(twoM + F)
);
r += (-0.58 * cos(MlesstwoD)
-0.46 * cos(twoD)
);
// from the orbital elements, the unit of the distance is in Earth radius, around 60.
distance = r;
distance_in_a = r/a;
// SG_LOG(SG_GENERAL, SG_INFO, "Running moon update");
rcoslatEcl = r * cos(latEcl);
xg = cos(lonEcl) * rcoslatEcl;
yg = sin(lonEcl) * rcoslatEcl;
zg = r * sin(latEcl);
xe = xg;
ye = yg * cosecl -zg * sinecl;
ze = yg * sinecl +zg * cosecl;
geoRa = atan2(ye, xe);
geoDec = atan2(ze, sqrt(xe*xe + ye*ye));
if (geoRa < 0)
geoRa += SGD_2PI;
rightAscension = geoRa;
declination = geoDec;
/* SG_LOG( SG_GENERAL, SG_INFO,
"Ra = (" << (SGD_RADIANS_TO_DEGREES *rightAscension)
<< "), Dec= (" << (SGD_RADIANS_TO_DEGREES *declination) << ")" ); */
// Moon age and phase calculation

12
simgear/ephemeris/moonpos.hxx
View File

@ -39,6 +39,7 @@ private:
double xg, yg; // the moon's rectangular geocentric coordinates
double ye, ze; // the moon's rectangular equatorial coordinates
double distance; // the moon's distance to the earth
double distance_in_a; // the moon's distance to the earth in unit of its semi-mayor axis a
double age; // the moon's age from 0 to 2pi
double phase; // the moon's phase
double log_I; // the moon's illuminance outside the atmosphere (logged)
@ -59,8 +60,9 @@ public:
MoonPos(double mjd);
MoonPos();
~MoonPos();
void updatePosition(double mjd, double lst, double lat, Star *ourSun);
// void newImage();
void updatePositionTopo(double mjd, double lst, double lat, Star *ourSun);
void updatePosition(double mjd, Star *ourSun);
// void newImage();
double getM() const;
double getw() const;
double getxg() const;
@ -68,6 +70,7 @@ public:
double getye() const;
double getze() const;
double getDistance() const;
double getDistanceInMayorAxis() const;
double getAge() const;
double getPhase() const;
double getLogIlluminance() const;
@ -109,6 +112,11 @@ inline double MoonPos::getDistance() const
return distance;
}
inline double MoonPos::getDistanceInMayorAxis() const
{
return distance_in_a;
}
inline double MoonPos::getAge() const
{
return age;

2
simgear/math/simd.hxx
View File

@ -82,7 +82,7 @@ inline T magnitude2(const simd4_t<T,N>& vi) {
template<typename T, int N>
inline simd4_t<T,N> interpolate(T tau, const simd4_t<T,N>& v1, const simd4_t<T,N>& v2) {
return (T(1)-tau)*v1 + tau*v2;
return v1 + tau*(v2-v1);
}
template<typename T, int N>

86
simgear/scene/sky/moon.cxx
View File

@ -1,9 +1,9 @@
// moon.hxx -- model earth's moon
//
// Written by Durk Talsma. Originally started October 1997, for distribution
// with the FlightGear project. Version 2 was written in August and
// September 1998. This code is based upon algorithms and data kindly
// provided by Mr. Paul Schlyter. (pausch@saaf.se).
// Written by Durk Talsma. Originally started October 1997, for distribution
// with the FlightGear project. Version 2 was written in August and
// September 1998. This code is based upon algorithms and data kindly
// provided by Mr. Paul Schlyter. (pausch@saaf.se).
//
// Separated out rendering pieces and converted to ssg by Curt Olson,
// March 2000
@ -69,7 +69,7 @@ SGMoon::~SGMoon( void ) {
osg::Node*
SGMoon::build( SGPath path, double moon_size ) {
osg::Node* orb = SGMakeSphere(moon_size, 15, 15);
osg::Node* orb = SGMakeSphere(moon_size, 40, 20);
osg::StateSet* stateSet = orb->getOrCreateStateSet();
stateSet->setRenderBinDetails(-5, "RenderBin");
@ -141,18 +141,18 @@ bool SGMoon::repaint( double moon_angle ) {
prev_moon_angle = moon_angle;
float moon_factor = 4*cos(moon_angle);
if (moon_factor > 1) moon_factor = 1.0;
if (moon_factor < -1) moon_factor = -1.0;
moon_factor = moon_factor/2 + 0.5;
osg::Vec4 color;
color[1] = sqrt(moon_factor);
color[0] = sqrt(color[1]);
color[2] = moon_factor * moon_factor;
color[2] *= color[2];
color[3] = 1.0;
gamma_correct_rgb( color._v );
orb_material->setDiffuse(osg::Material::FRONT_AND_BACK, color);
@ -162,22 +162,74 @@ bool SGMoon::repaint( double moon_angle ) {
// reposition the moon at the specified right ascension and
// declination, offset by our current position (p) so that it appears
// fixed at a great distance from the viewer. Also add in an optional
// rotation (i.e. for the current time of day.)
bool SGMoon::reposition( double rightAscension, double declination,
double moon_dist )
{
osg::Matrix T2, RA, DEC;
// declination from the center of Earth. Because the view is actually
// offset by our current position (p), we first evaluate our current
// position w.r.t the Moon and then shift to the articial center of
// earth before shifting to the rendered moon distance. This allows to
// implement any parallax effects. moon_dist_bare is expected to not
// change during the rendering, it gives us the normalisation factors
// between real distances and units used in the
// rendering. moon_dist_fact is any extra factors to put the moon
// further or closer.
bool SGMoon::reposition( double rightAscension, double declination,
double moon_dist_bare, double moon_dist_factor,
double lst, double lat, double alt )
{
osg::Matrix TE, T2, RA, DEC;
// semi mayor axis
const double moon_a_in_rearth = 60.266600;
// average (we could also account for equatorial streching like in
// oursun.cxx if required)
const double earth_radius_in_meters = 6371000.0;
//local hour angle in radians
double lha;
// in unit of the rendering
double moon_dist;
double earth_radius, viewer_radius;
double xp,yp,zp;
//rendered earth radius according to what has been specified by
//moon_dist_bare
earth_radius = moon_dist_bare/moon_a_in_rearth;
//how far are we from the center of Earth
viewer_radius = (1.0 + alt/earth_radius_in_meters)*earth_radius;
// the local hour angle of the moon, .i.e. its angle with respect
// to the meridian of the viewer
lha = lst - rightAscension;
// the shift vector of the observer w.r.t. earth center (funny
// convention on x?)
zp = viewer_radius * sin(lat);
yp = viewer_radius * cos(lat)*cos(lha);
xp = viewer_radius * cos(lat)*sin(-lha);
//rotate along the z axis
RA.makeRotate(rightAscension - 90.0 * SGD_DEGREES_TO_RADIANS,
osg::Vec3(0, 0, 1));
//rotate along the rotated x axis
DEC.makeRotate(declination, osg::Vec3(1, 0, 0));
//move to the center of Earth
TE.makeTranslate(osg::Vec3(-xp,-yp,-zp));
//move the moon from the center of Earth to moon_dist
moon_dist = moon_dist_bare * moon_dist_factor;
T2.makeTranslate(osg::Vec3(0, moon_dist, 0));
moon_transform->setMatrix(T2*DEC*RA);
// cout << " viewer radius= " << viewer_radius << endl;
// cout << " xp yp zp= " << xp <<" " << yp << " " << zp << endl;
// cout << " lha= " << lha << endl;
// cout << " moon_dist_bare= " << moon_dist_bare << endl;
// cout << " moon_dist_factor= " << moon_dist_factor << endl;
// cout << " moon_dist= " << moon_dist << endl;
moon_transform->setMatrix(T2*TE*DEC*RA);
return true;
}

9
simgear/scene/sky/moon.hxx
View File

@ -65,11 +65,12 @@ public:
bool repaint( double moon_angle );
// reposition the moon at the specified right ascension and
// declination, offset by our current position (p) so that it
// appears fixed at a great distance from the viewer. Also add in
// an optional rotation (i.e. for the current time of day.)
// declination, at moon_dist_bare*moon_dist_factor from the center
// of Earth. lst, lat and alt are need to estimate where is the
// center of Earth from the current view).
bool reposition( double rightAscension, double declination,
double moon_dist );
double moon_dist_bare, double moon_dist_factor,
double lst, double lat, double alt );
};

13
simgear/scene/sky/sky.cxx
View File

@ -152,7 +152,7 @@ bool SGSky::reposition( const SGSkyState &st, const SGEphemeris& eph, double dt
double angleRad = SGMiscd::deg2rad(angle);
SGVec3f zero_elev, view_up;
double lon, lat, alt;
double lon, lat, alt, lst;
SGGeod geodZeroViewPos = SGGeod::fromGeodM(st.pos_geod, 0);
zero_elev = toVec3f( SGVec3d::fromGeod(geodZeroViewPos) );
@ -165,7 +165,9 @@ bool SGSky::reposition( const SGSkyState &st, const SGEphemeris& eph, double dt
lon = st.pos_geod.getLongitudeRad();
lat = st.pos_geod.getLatitudeRad();
alt = st.pos_geod.getElevationM();
// Local sidereal time
lst = angleRad + lon;
dome->reposition( zero_elev, alt, lon, lat, st.spin );
osg::Matrix m = osg::Matrix::rotate(angleRad, osg::Vec3(0, 0, -1));
@ -178,7 +180,12 @@ bool SGSky::reposition( const SGSkyState &st, const SGEphemeris& eph, double dt
double moon_ra = eph.getMoonRightAscension();
double moon_dec = eph.getMoonDeclination();
moon->reposition( moon_ra, moon_dec, st.moon_dist );
double moon_r = eph.getMoonDistanceInMayorAxis();
//this allows to render the moon closer to the viewer when the
//moon is closer to the center of Earth, times any articial extra factors
double moon_dist_factor = moon_r * st.moon_dist_factor;
moon->reposition( moon_ra, moon_dec, st.moon_dist_bare, moon_dist_factor, lst, lat, alt );
for ( unsigned i = 0; i < cloud_layers.size(); ++i ) {
if ( cloud_layers[i]->getCoverage() != SGCloudLayer::SG_CLOUD_CLEAR ||

3
simgear/scene/sky/sky.hxx
View File

@ -63,7 +63,8 @@ struct SGSkyState
double gst; //!< GMT side real time.
double sun_dist; //!< the sun's distance from the current view point
// (to keep it inside your view volume).
double moon_dist;//!< The moon's distance from the current view point.
double moon_dist_bare ;//!< The moon's semi-mayor axis in the rendering (constant)
double moon_dist_factor ;//!< Any factor that are needed to artificially change the moon distance
double sun_angle;
};