// -*- C++ -*-
//  plane.cc by George Vanecek Jr., June 1994
//
//  bug fixes 2016.1.21 Glenn Burkhardt
//      - fix index out of bounds error
//      - correct computation of epsilon; need 'n' and 'd' before computing
//

#include "plane.h"

// Computes the plane equation using Newell's averaging algorithm.
Plane::Plane( const Counter nPoints, const Point points[] )
: n(0.0,0.0,0.0), d(0.0), eps(0.0)
{
  assert( nPoints > 2 );
  Vector avrPnt = Point(0,0,0);
  for( Index i = 0; i < nPoints; ++i ) {
    avrPnt += points[i];
    n      += Vector(points[i]) ^ Vector(points[(i+1) % nPoints]);
  }

  n.normalize();
  d = normal() * ((-1.0 / nPoints) * avrPnt );

  for( Index i = 0; i < nPoints; ++i )
      updateEpsilon( points[i] );
}

// Compute the intersection point with the transversal line (p,q).
Point Plane::onPoint( const Point &p, const Point &q ) const
{
  const Vector v(q - p);
  const double c = normal() * v;
  assert( c != 0.0 );
  const double t = -sDistance(p) / c;
  return p + t * v;
}

void Plane::updateEpsilon ( const Point& p )
{
  double d = sDistance(p);
  if( d < 0.0 )
    d = -d;
  if( d > eps)
    eps = d;
}