//_____________________________________________________________________________
//  TG3Plane: class representing 2D plane in 3D space
//  Feb 03 2001 P.Murat
//_____________________________________________________________________________

#include "TMath.h"
#include "TG3Plane.hh"
#include "TLine3D.hh"


ClassImp(TG3Plane)

//_____________________________________________________________________________
TG3Plane::TG3Plane() {
}

//_____________________________________________________________________________
TG3Plane::TG3Plane(const TVector3& R0, const TVector3& Normal) {
  fR0     = R0;
  fNormal = Normal.Unit();
}

//_____________________________________________________________________________
TG3Plane::~TG3Plane() {
}


//_____________________________________________________________________________
Int_t TG3Plane::FindIntersection(const TLine3D& Line, TVector3& Point) 
{
  // returns 3D `Point' of intersection between the `Line' and *this plane
  
  int rc;
  TVector3 pos;
  TVector3 dir;

  Line.GetPosition(pos);
  Line.GetDirection(dir);

  Double_t denom = dir.Dot(fNormal);

  if (TMath::Abs(denom) > 1.e-10) {
    Double_t t = (fR0-pos).Dot(fNormal)/denom;

    Point.SetXYZ(pos.X()+t*dir.X(),
		 pos.Y()+t*dir.Y(),
		 pos.Z()+t*dir.Z());
    rc = 0;
  }
  else {
    Point.SetXYZ(0.,0.,0.);
    rc = -1;
  }
  return rc;
}