add initial support to display variable brightness for variable stars

Author: henrysky

src/core/modules/Star.hpp

@@ -429,6 +429,36 @@ struct Star
       pmdec = sky_orbit_vel.dot(q2) * 1000.;
       StelUtils::rectToSphe(&ra, &dec, v);
    }
+
+   inline void getVarStarOffset(double epoch, double &offset) const // get brightness offset for variable stars (not actual brightness)
+   {
+      StarId star_id;  // star ID
+      if (getGaia() == 0)
+      {
+         star_id = getHip();
+      }
+      else
+      {
+         star_id = getGaia();
+      }
+      double period = StarMgr::getGcvsPeriod(star_id);
+      if (period == 0.)  // not a variable star
+         return;
+      double dyrs = (epoch - STAR_CATALOG_JDEPOCH) / 365.25;
+      double min1mag = StarMgr::getGcvsMinMagnitude(star_id) * 1000.;
+      double maxmag = StarMgr::getGcvsMaxMagnitude(star_id) * 1000.;
+      double epoch_offset = (StarMgr::getGcvsEpoch(star_id) - STAR_CATALOG_JDEPOCH) / 365.25;
+      double phase = fmod(dyrs - epoch_offset, period) / period;
+   
+      if (period && min1mag && maxmag && min1mag > maxmag)
+      {
+         double amplitude = (min1mag - maxmag) / 2.;
+         if (phase < 0.0)
+            phase += 1.0;
+         // sine wave
+         offset = amplitude * sin(2. * M_PI * phase);
+      }
+   }   
 };
 
 struct Star1 : public Star<Star1>

src/core/modules/StarWrapper.cpp

@@ -310,7 +310,9 @@ QString StarWrapper1::getInfoString(const StelCore *core, const InfoStringGroup&
 	{
 		magOffset = 5.f * log10(s->getPlx()/Plx);
 	} 
-	oss << getMagnitudeInfoString(core, flags, 2, magOffset);
+	double variable_magoffset = 0.0;
+	s->getVarStarOffset(core->getJDE(), variable_magoffset);
+	oss << getMagnitudeInfoString(core, flags, 2, magOffset + variable_magoffset / 1000.);
 
 	// should use Plx from getPlx because Plx can change with time, but not absolute magnitude
 	if ((flags&AbsoluteMagnitude) && s->getPlx())
@@ -668,7 +670,9 @@ QString StarWrapper2::getInfoString(const StelCore *core, const InfoStringGroup&
 			oss << QString("%1: <b>%2</b>").arg(q_("Type"), objectTypeI18nStr) << "<br />";
 	}
 
-	oss << getMagnitudeInfoString(core, flags, 2);
+	double variable_magoffset = 0.0;
+	s->getVarStarOffset(core->getJDE(), variable_magoffset);
+	oss << getMagnitudeInfoString(core, flags, 2, variable_magoffset / 1000.);
 
 	double RA, DEC, pmra, pmdec;
 	double Plx = s->getPlx();
@@ -895,7 +899,9 @@ QString StarWrapper3::getInfoString(const StelCore *core, const InfoStringGroup&
 			oss << QString("%1: <b>%2</b>").arg(q_("Type"), objectTypeI18nStr) << "<br />";
 	}
 
-	oss << getMagnitudeInfoString(core, flags, 2);
+	double variable_magoffset = 0.0;
+	s->getVarStarOffset(core->getJDE(), variable_magoffset);
+	oss << getMagnitudeInfoString(core, flags, 2, variable_magoffset / 1000.);
 
 	if (flags&Extra)
 	{

src/core/modules/ZoneArray.cpp

@@ -483,6 +483,11 @@ void SpecialZoneArray<Star>::draw(StelPainter* sPainter, int index, bool isInsid
 			Vec3d u = (r * (1. + pmr0 * dyrs) + pmvec0 * dyrs) * f;
 			v.set(u[0], u[1], u[2]);
 		}
+		// take variable star brightness delta into account
+		double variable_magoffset = 0.0;
+		s->getVarStarOffset(core->getJDE(), variable_magoffset);
+		starMag += variable_magoffset;
+
 		// recompute magIndex with the new magnitude
 		magIndex = static_cast<int>((starMag - (mag_min - 7000.)) * 0.02);  // 1 / (50 milli-mag)
 

src/core/modules/ZoneArray.hpp

@@ -111,7 +111,8 @@ class ZoneArray
 					  const RCMag* rcmag_table, int limitMagIndex, StelCore* core,
 					  int maxMagStarName, float names_brightness,
 					  const QVector<SphericalCap>& boundingCaps,
-					  const bool withAberration, const Vec3d vel, const double withParallax, const Vec3d diffPos) const = 0;
+					  const bool withAberration, const Vec3d vel, const double withParallax, 
+					  const Vec3d diffPos) const = 0;
 
 	//! Get whether or not the catalog was successfully loaded.
 	//! @return @c true if at least one zone was loaded, otherwise @c false
@@ -183,7 +184,8 @@ class SpecialZoneArray : public ZoneArray
 	          const RCMag *rcmag_table, int limitMagIndex, StelCore* core,
 	          int maxMagStarName, float names_brightness,
 	          const QVector<SphericalCap>& boundingCaps,
-	          const bool withAberration, const Vec3d vel, const double withParallax, const Vec3d diffPos) const override;
+	          const bool withAberration, const Vec3d vel, const double withParallax, 
+			  const Vec3d diffPos) const override;
 
 	void searchAround(const StelCore* core, int index, const Vec3d &v, const double withParallax, 
 					  const Vec3d diffPos, double cosLimFov, QList<StelObjectP > &result) override;