void Comet::drawComa(StelCore* core, StelProjector::ModelViewTranformP transfo)
{
// Find rotation matrix from 0/0/1 to viewdirection! crossproduct for axis (normal vector), dotproduct for angle.
Vec3d eclposNrm=eclipticPos - core->getObserverHeliocentricEclipticPos() ; eclposNrm.normalize();
Mat4d comarot=Mat4d::rotation(Vec3d(0.0, 0.0, 1.0)^(eclposNrm), std::acos(Vec3d(0.0, 0.0, 1.0).dot(eclposNrm)) );
StelProjector::ModelViewTranformP transfo2 = transfo->clone();
transfo2->combine(comarot);
StelPainter* sPainter = new StelPainter(core->getProjection(transfo2));
glEnable(GL_BLEND);
glBlendFunc(GL_ONE, GL_ONE);
glDisable(GL_CULL_FACE);
// GZ: For the coma, we can use extinction via atmosphere.
// In addition, light falloff is a bit reduced for better visibility. Power basis should be 0.4, we use 0.6.
float minSkyMag=core->getSkyDrawer()->getLimitMagnitude();
float mag100pct=minSkyMag-6.0f; // should be 5, but let us draw it a bit brighter.
float magDrop=getVMagnitudeWithExtinction(core)-mag100pct;
float magFactor=std::pow(0.6f , magDrop);
magFactor=qMin(magFactor, 2.0f); // Limit excessively bright display.
comaTexture->bind();
sPainter->setColor(magFactor,magFactor,0.6f*magFactor);
sPainter->setArrays((Vec3d*)comaVertexArr.constData(), (Vec2f*)comaTexCoordArr.constData());
sPainter->drawFromArray(StelPainter::Triangles, comaVertexArr.size()/3);
glDisable(GL_BLEND);
if (sPainter)
delete sPainter;
sPainter=NULL;
}
void Comet::drawTail(StelCore* core, StelProjector::ModelViewTranformP transfo, bool gas)
{
// Find rotation matrix from 0/0/1 to eclipticPosition: crossproduct for axis (normal vector), dotproduct for angle.
Vec3d eclposNrm=eclipticPos; eclposNrm.normalize();
Mat4d tailrot=Mat4d::rotation(Vec3d(0.0, 0.0, 1.0)^(eclposNrm), std::acos(Vec3d(0.0, 0.0, 1.0).dot(eclposNrm)) );
StelProjector::ModelViewTranformP transfo2 = transfo->clone();
transfo2->combine(tailrot);
if (!gas) {
CometOrbit* orbit=(CometOrbit*)userDataPtr;
Vec3d velocity=orbit->getVelocity(); // [AU/d]
// This was a try to rotate a straight parabola somewhat away from the antisolar direction.
//Mat4d dustTailRot=Mat4d::rotation(eclposNrm^(-velocity), 0.15f*std::acos(eclposNrm.dot(-velocity))); // GZ: This scale factor of 0.15 is empirical from photos of Halley and Hale-Bopp.
// The curved tail is curved towards positive X. We first rotate around the Z axis into a direction opposite of the motion vector, then again the antisolar rotation applies.
Mat4d dustTailRot=Mat4d::zrotation(atan2(velocity[1], velocity[0]) + M_PI);
transfo2->combine(dustTailRot);
// In addition, we let the dust tail already start with a light tilt.
Mat4d dustTailYrot=Mat4d::yrotation(5.0f*velocity.length()); // again, this is pretty ad-hoc, feel free to improve!
transfo2->combine(dustTailYrot);
}
StelPainter* sPainter = new StelPainter(core->getProjection(transfo2));
glEnable(GL_BLEND);
glBlendFunc(GL_ONE, GL_ONE);
glDisable(GL_CULL_FACE);
// GZ: If we use getVMagnitudeWithExtinction(), a head extincted in the horizon mist can completely hide an otherwise frighteningly long tail.
// we must use unextincted mag, but mix/dim with atmosphere/sky brightness.
// In addition, light falloff is a bit reduced for better visibility. Power basis should be 0.4, we use 0.6.
//float magfactor=std::pow(0.4f , getVMagnitudeWithExtinction(core));
float magFactor=std::pow(0.6f , getVMagnitude(core));
if (core->getSkyDrawer()->getFlagHasAtmosphere())
{
// Mix with sky brightness and light pollution: This is very ad-hoc, if someone finds a better solution, please go ahead!
// Light pollution:
float bortleIndexFactor=0.1f * (11 - core->getSkyDrawer()->getBortleScaleIndex());
magFactor*= bortleIndexFactor*bortleIndexFactor; // GZ-Guesstimate for light pollution influence
// sky brightness: This is about 10 for twilight where bright comet tails should already be visible. Dark night is close to 0.
float avgAtmLum=GETSTELMODULE(LandscapeMgr)->getAtmosphereAverageLuminance();
float atmLumFactor=(15.0f-avgAtmLum)/15.0f; if (atmLumFactor<0.05f) atmLumFactor=0.05f; //atmLumFactor=std::sqrt(atmLumFactor);
magFactor*=atmLumFactor*atmLumFactor;
}
magFactor*=(gas? 0.9 : dustTailBrightnessFactor); // TBD: empirical adjustment for texture brightness.
magFactor=qMin(magFactor, 1.05f); // Limit excessively bright display.
gasTailTexture->bind();
if (gas) {
//gasTailTexture->bind();
sPainter->setColor(0.15f*magFactor,0.15f*magFactor,0.6f*magFactor);
sPainter->setArrays((Vec3d*)gastailVertexArr.constData(), (Vec2f*)gastailTexCoordArr.constData());
sPainter->drawFromArray(StelPainter::Triangles, gastailIndices.size(), 0, true, gastailIndices.constData());
} else {
//dustTailTexture->bind();
sPainter->setColor(magFactor, magFactor,0.6f*magFactor);
//sPainter->setArrays((Vec3d*)dusttailVertexArr.constData(), (Vec2f*)dusttailTexCoordArr.constData());
//sPainter->drawFromArray(StelPainter::Triangles, dusttailIndices.size(), 0, true, dusttailIndices.constData());
sPainter->setArrays((Vec3d*)dusttailVertexArr.constData(), (Vec2f*)gastailTexCoordArr.constData());
sPainter->drawFromArray(StelPainter::Triangles, gastailIndices.size(), 0, true, gastailIndices.constData());
}
glDisable(GL_BLEND);
if (sPainter)
delete sPainter;
sPainter=NULL;
}