oomph::IntersectionChecker Namespace Reference

Namespace for intersection checker. More...

Functions
bool	intersects (const Vector< Vector< double > > &first_segment_vertex, const Vector< Vector< double > > &second_segment_vertex, const double &epsilon_parallel=1.0e-15)

Detailed Description

Namespace for intersection checker.

Function Documentation

intersects()

bool oomph::IntersectionChecker::intersects	(	const Vector< Vector< double > > &	first_segment_vertex,
		const Vector< Vector< double > > &	second_segment_vertex,
		const double &	epsilon_parallel = 1.0e-15
	)

Check if finite-length line segments specified by end points intersect (true) or not (false). From http://paulbourke.net/geometry/lineline2d/ C++ contribution by Damian Coventry.

 {
  
  double denom = ((first_segment_vertex[1][1] - first_segment_vertex[0][1])*
                  (second_segment_vertex[1][0] - second_segment_vertex[0][0])) -
   ((first_segment_vertex[1][0] - first_segment_vertex[0][0])*
    (second_segment_vertex[1][1] - second_segment_vertex[0][1]));
  
  double nume_a = ((first_segment_vertex[1][0] - first_segment_vertex[0][0])*
                   (second_segment_vertex[0][1] - first_segment_vertex[0][1])) -
   ((first_segment_vertex[1][1] - first_segment_vertex[0][1])*
    (second_segment_vertex[0][0] - first_segment_vertex[0][0]));
  
  double nume_b = ((second_segment_vertex[1][0] - second_segment_vertex[0][0])*
                   (second_segment_vertex[0][1] - first_segment_vertex[0][1])) -
   ((second_segment_vertex[1][1] - second_segment_vertex[0][1])*
    (second_segment_vertex[0][0] - first_segment_vertex[0][0]));
  
  if(std::fabs(denom) < epsilon_parallel)
   {
    if( (std::fabs(nume_a) < epsilon_parallel) &&
        (std::fabs(nume_b) < epsilon_parallel) )
     {
      return false; //COINCIDENT;
     }
    return false; //PARALLEL;
   }
  
  double ua = nume_a / denom;
  double ub = nume_b / denom;
  
  if( (ua >= 0.0) && (ua <= 1.0) && (ub >= 0.0) && (ub <= 1.0) )
   {
    /* // Get the intersection point. */
    /* intersection[0] = second_segment_vertex[0][0] +  */
    /*  ua*(second_segment_vertex[1][0] - second_segment_vertex[0][0]); */
    /* intersection[1] = second_segment_vertex[0][1] +  */
    /*  ua*(second_segment_vertex[1][1] - second_segment_vertex[0][1]); */
    
    return true; //INTERESECTING;
   }
  
  return false; //NOT_INTERESECTING;
 }

References boost::multiprecision::fabs().

Referenced by oomph::StefanBoltzmannHelper::setup_stefan_boltzmann_visibility().