PostGIS  2.2.8dev-r@@SVN_REVISION@@

## ◆ edge_point_side()

 static int edge_point_side ( const GEOGRAPHIC_EDGE * e, const GEOGRAPHIC_POINT * p )
static

Returns -1 if the point is to the left of the plane formed by the edge, 1 if the point is to the right, and 0 if the point is on the plane.

Definition at line 644 of file lwgeodetic.c.

Referenced by edge_point_on_plane(), and sphere_signed_area().

645 {
646  POINT3D normal, pt;
647  double w;
648  /* Normal to the plane defined by e */
649  robust_cross_product(&(e->start), &(e->end), &normal);
650  normalize(&normal);
651  geog2cart(p, &pt);
652  /* We expect the dot product of with normal with any vector in the plane to be zero */
653  w = dot_product(&normal, &pt);
654  LWDEBUGF(4,"dot product %.9g",w);
655  if ( FP_IS_ZERO(w) )
656  {
657  LWDEBUG(4, "point is on plane (dot product is zero)");
658  return 0;
659  }
660
661  if ( w < 0 )
662  return -1;
663  else
664  return 1;
665 }
void robust_cross_product(const GEOGRAPHIC_POINT *p, const GEOGRAPHIC_POINT *q, POINT3D *a)
Computes the cross product of two vectors using their lat, lng representations.
Definition: lwgeodetic.c:584
void normalize(POINT3D *p)
Normalize to a unit vector.
Definition: lwgeodetic.c:565
char * w
Definition: cu_out_twkb.c:25
#define LWDEBUG(level, msg)
Definition: lwgeom_log.h:50
#define FP_IS_ZERO(A)
static double dot_product(const POINT3D *p1, const POINT3D *p2)
Convert cartesion coordinates on unit sphere to lon/lat coordinates static void cart2ll(const POINT3D...
Definition: lwgeodetic.c:396
GEOGRAPHIC_POINT start
Definition: lwgeodetic.h:43
GEOGRAPHIC_POINT end
Definition: lwgeodetic.h:44
void geog2cart(const GEOGRAPHIC_POINT *g, POINT3D *p)
Convert spherical coordinates to cartesion coordinates on unit sphere.
Definition: lwgeodetic.c:354
#define LWDEBUGF(level, msg,...)
Definition: lwgeom_log.h:55
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