//
// Update the position of the moon image in the sky
//
void CMoonImage::Reposition (sgVec3 p, double theta, double lst, double lat,
double ra, double dec, double spin)
{
sgMat4 LST, LAT, RA, DEC, D, SCALE, ECLIPTIC, SPIN;
sgVec3 axis;
sgVec3 v;
// Create scaling matrix for moon illusion (appears larger near horizon)
float scale = 1.0f;
sgMakeIdentMat4 (SCALE);
float maxMagnification = 0.5f;
float minThreshold = DegToRad (80.0f);
float maxThreshold = DegToRad (95.0f);
float span = maxThreshold - minThreshold;
if ((theta >= minThreshold) && (theta <= maxThreshold)) {
sgMat4 I;
sgMakeIdentMat4 (I);
scale = 1.0f + (maxMagnification * (theta - minThreshold) / span);
sgScaleMat4 (SCALE, I, scale);
}
// Rotation matrix for latitude
sgSetVec3 (axis, -1.0f, 0, 0);
sgMakeRotMat4 (LAT, 90.0f-(float)lat, axis);
// Rotation matrix for local sidereal time, converted from h to deg
sgSetVec3 (axis, 0, 0, -1.0f);
sgMakeRotMat4 (LST, ((float)lst * 15), axis);
// Rotation matrix for right ascension
sgSetVec3 (axis, 0, 0, 1);
sgMakeRotMat4 (RA, RadToDeg ((float)ra), axis);
// Rotation matrix for declination
sgSetVec3 (axis, 1, 0, 0);
sgMakeRotMat4 (DEC, 90.0f - RadToDeg ((float)dec), axis);
// Translate moon distance
sgSetVec3 (v, 0, 0, distance);
sgMakeTransMat4 (D, v);
// Rotate to align moon equator with ecliptic
sgSetVec3 (axis, 1.0f, 0, 0);
sgMakeRotMat4 (ECLIPTIC, 90.0f, axis);
/// Rotate the moon image accurately towards the sun position
sgSetVec3 (axis, 0, 0, 1);
sgMakeRotMat4 (SPIN, spin, axis);
// Combine all transforms
sgMakeIdentMat4 (T);
sgPreMultMat4 (T, LAT);
sgPreMultMat4 (T, LST);
sgPreMultMat4 (T, RA);
sgPreMultMat4 (T, DEC);
sgPreMultMat4 (T, D);
sgPreMultMat4 (T, ECLIPTIC);
sgPreMultMat4 (T, SPIN);
}
//
// Update the position of the moon image in the sky
//
void CMoonImage::Reposition (sgVec3 p, double theta, double lst, double lat,
double ra, double dec, double spin)
{
sgMat4 LST, LAT, RA, DEC, D, SCALE, ECLIPTIC, SPIN;
sgVec3 axis;
sgVec3 v;
// Create scaling matrix for moon illusion (appears larger near horizon)
float scale = 1.0f;
sgMakeIdentMat4 (SCALE);
float maxMagnification = 0.5f;
float minThreshold = DegToRad (80.0f);
float maxThreshold = DegToRad (95.0f);
float span = maxThreshold - minThreshold;
if ((theta >= minThreshold) && (theta <= maxThreshold)) {
sgMat4 I;
sgMakeIdentMat4 (I);
scale = 1.0f + (maxMagnification * (theta - minThreshold) / span);
sgScaleMat4 (SCALE, I, scale);
}
// Rotation matrix for latitude
sgSetVec3 (axis, -1.0f, 0, 0);
sgMakeRotMat4 (LAT, 90.0f-(float)lat, axis);
// Rotation matrix for local sidereal time, converted from h to deg
sgSetVec3 (axis, 0, 0, -1.0f);
sgMakeRotMat4 (LST, ((float)lst * 15), axis);
// Rotation matrix for right ascension
sgSetVec3 (axis, 0, 0, 1);
sgMakeRotMat4 (RA, RadToDeg ((float)ra), axis);
// Rotation matrix for declination
sgSetVec3 (axis, 1, 0, 0);
sgMakeRotMat4 (DEC, 90.0f - RadToDeg ((float)dec), axis);
// Translate moon distance
sgSetVec3 (v, 0, 0, distance);
sgMakeTransMat4 (D, v);
// Rotate to align moon equator with ecliptic
sgSetVec3 (axis, 1.0f, 0, 0);
sgMakeRotMat4 (ECLIPTIC, 90.0f, axis);
/// Rotate the moon image accurately towards the sun position
sgSetVec3 (axis, 0, 0, 1);
sgMakeRotMat4 (SPIN, spin, axis);
// Combine all transforms
sgMakeIdentMat4 (T);
sgPreMultMat4 (T, LAT);
sgPreMultMat4 (T, LST);
sgPreMultMat4 (T, RA);
sgPreMultMat4 (T, DEC);
sgPreMultMat4 (T, D);
sgPreMultMat4 (T, ECLIPTIC);
sgPreMultMat4 (T, SPIN);
/*
char debug[256];
double jd = CTimeManager::Instance().GetJulianDate();
SDateTime dt = CTimeManager::Instance().GetLocalDateTime ();
sprintf (debug, "JD=%f D=%d/%d/%d T=%d:%d RA=%f Dec=%f", jd,
dt.date.year, dt.date.month, dt.date.day, dt.time.hour, dt.time.minute,
RadToDeg(ra), RadToDeg(dec));
DrawNoticeToUser (debug, 1);
*/
}
