anonymous_namespace{SkyNode.cpp}::Sun Struct Reference

List of all members.

Public Member Functions
	Sun ()
osg::Vec3d	getPosition (int year, int month, int date, double hoursUTC) const

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Detailed Description

Definition at line 277 of file SkyNode.cpp.

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Constructor & Destructor Documentation

anonymous_namespace{SkyNode.cpp}::Sun::Sun

(

)

[inline]

Definition at line 279 of file SkyNode.cpp.

{ }

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Member Function Documentation

osg::Vec3d anonymous_namespace{SkyNode.cpp}::Sun::getPosition	(	int	year,
		int	month,
		int	date,
		double	hoursUTC
	)		const [inline]

Definition at line 282 of file SkyNode.cpp.

        {
            double JD = getJulianDate(year, month, date);
            double JD1 = (JD - JD2000);                         // julian time since JD2000 epoch
            double JC = JD1/36525.0;                            // julian century

            double mu = 282.937348 + 0.00004707624*JD1 + 0.0004569*(JC*JC);

            double epsilon = 280.466457 + 0.985647358*JD1 + 0.000304*(JC*JC);

            // orbit eccentricity:
            double E = 0.01670862 - 0.00004204 * JC;

            // mean anomaly of the perihelion
            double M = epsilon - mu;

            // perihelion anomaly:
            double v =
                M + 
                360.0*E*sin(d2r(M))/osg::PI + 
                900.0*(E*E)*sin(d2r(2*M))/4*osg::PI - 
                180.0*(E*E*E)*sin(d2r(M))/4.0*osg::PI;

            // longitude of the sun in ecliptic coordinates:
            double sun_lon = d2r(v - 360.0 + mu); // lambda
            nrad2(sun_lon);

            // angle between the ecliptic plane and the equatorial plane
            double zeta = d2r(23.4392); // zeta

            // latitude of the sun on the ecliptic plane:
            double omega = d2r(0.0);

            // latitude of the sun with respect to the equatorial plane (solar declination):
            double sun_lat = asin( sin(sun_lon)*sin(zeta) );
            nrad2(sun_lat);

            // finally, adjust for the time of day (rotation of the earth)
            double time_r = hoursUTC/24.0; // 0..1
            nrad(sun_lon); // clamp to 0..TWO_PI
            double sun_r = sun_lon/TWO_PI; // convert to 0..1

            // rotational difference between UTC and current time
            double diff_r = sun_r - time_r;
            double diff_lon = TWO_PI * diff_r;

            // apparent sun longitude.
            double app_sun_lon = sun_lon - diff_lon + osg::PI;
            nrad2(app_sun_lon);

#if 0
            OE_INFO
                << "sun lat = " << r2d(sun_lat) 
                << ", sun lon = " << r2d(sun_lon)
                << ", time delta_lon = " << r2d(diff_lon)
                << ", app sun lon = " << r2d(app_sun_lon)
                << std::endl;
#endif

            return osg::Vec3d(
                cos(sun_lat) * cos(-app_sun_lon),
                cos(sun_lat) * sin(-app_sun_lon),
                sin(sun_lat) );
        }

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The documentation for this struct was generated from the following file:

• /home/cube/sources/osgearth/src/osgEarthUtil/SkyNode.cpp