/**
 * \author mdejong
 */

    /**
     * Class to check whether a photon emitted from a position along the
     * z-axis crosses a DOM (approximated by a disc)
     * first, inefficient version
     */

    class DomCrossing {

    private:
      double __Rdom;
    public:

      DomCrossing(const double Rdom):__Rdom(Rdom)
      {}
      ~DomCrossing()
      {}

      bool operator()(const double theta,
                      const double phi,
                      const double z,
                      const double R,
                      const double dscat)
      {
	using namespace JGEOMETRY3D;

        const JVector3D p0(R,0,0);
        const JVector3D n(sin(theta),0,cos(theta));
        const JVector3D l0(0,0,z);
        const JVector3D l(sin(theta)*cos(phi),sin(theta)*sin(phi),cos(theta));

        const double d = JVector3D(p0-l0).getDot(n)/l.getDot(n);

        if(d<0) return false;

        const JVector3D crossing = l0+JVector3D(l.getX()*d,l.getY()*d,l.getZ()*d);

        const double hitdist = (p0-crossing).getLength();

        const double dist = sqrt(z*z+R*R);

        if(hitdist<__Rdom&&dscat>=dist) return true;
        else return false;

      }

    };

    //  DomCrossing shadow;