PostGIS  2.5.2dev-r@@SVN_REVISION@@

◆ edge_intersection()

int edge_intersection ( const GEOGRAPHIC_EDGE e1,
const GEOGRAPHIC_EDGE e2,
GEOGRAPHIC_POINT g 
)

Returns true if an intersection can be calculated, and places it in *g.

Returns false otherwise.

Definition at line 1105 of file lwgeodetic.c.

References dot_product(), edge_contains_point(), GEOGRAPHIC_EDGE::end, FP_EQUALS, geographic_point_equals(), GEOGRAPHIC_POINT::lat, GEOGRAPHIC_POINT::lon, LW_FALSE, LW_TRUE, LWDEBUG, LWDEBUGF, normalize(), rad2deg, robust_cross_product(), GEOGRAPHIC_EDGE::start, unit_normal(), POINT3D::x, POINT3D::y, and POINT3D::z.

Referenced by circ_tree_distance_tree_internal(), and test_edge_intersection().

1106 {
1107  POINT3D ea, eb, v;
1108  LWDEBUGF(4, "e1 start(%.20g %.20g) end(%.20g %.20g)", e1->start.lat, e1->start.lon, e1->end.lat, e1->end.lon);
1109  LWDEBUGF(4, "e2 start(%.20g %.20g) end(%.20g %.20g)", e2->start.lat, e2->start.lon, e2->end.lat, e2->end.lon);
1110 
1111  LWDEBUGF(4, "e1 start(%.20g %.20g) end(%.20g %.20g)", rad2deg(e1->start.lon), rad2deg(e1->start.lat), rad2deg(e1->end.lon), rad2deg(e1->end.lat));
1112  LWDEBUGF(4, "e2 start(%.20g %.20g) end(%.20g %.20g)", rad2deg(e2->start.lon), rad2deg(e2->start.lat), rad2deg(e2->end.lon), rad2deg(e2->end.lat));
1113 
1114  if ( geographic_point_equals(&(e1->start), &(e2->start)) )
1115  {
1116  *g = e1->start;
1117  return LW_TRUE;
1118  }
1119  if ( geographic_point_equals(&(e1->end), &(e2->end)) )
1120  {
1121  *g = e1->end;
1122  return LW_TRUE;
1123  }
1124  if ( geographic_point_equals(&(e1->end), &(e2->start)) )
1125  {
1126  *g = e1->end;
1127  return LW_TRUE;
1128  }
1129  if ( geographic_point_equals(&(e1->start), &(e2->end)) )
1130  {
1131  *g = e1->start;
1132  return LW_TRUE;
1133  }
1134 
1135  robust_cross_product(&(e1->start), &(e1->end), &ea);
1136  normalize(&ea);
1137  robust_cross_product(&(e2->start), &(e2->end), &eb);
1138  normalize(&eb);
1139  LWDEBUGF(4, "e1 cross product == POINT(%.12g %.12g %.12g)", ea.x, ea.y, ea.z);
1140  LWDEBUGF(4, "e2 cross product == POINT(%.12g %.12g %.12g)", eb.x, eb.y, eb.z);
1141  LWDEBUGF(4, "fabs(dot_product(ea, eb)) == %.14g", fabs(dot_product(&ea, &eb)));
1142  if ( FP_EQUALS(fabs(dot_product(&ea, &eb)), 1.0) )
1143  {
1144  LWDEBUGF(4, "parallel edges found! dot_product = %.12g", dot_product(&ea, &eb));
1145  /* Parallel (maybe equal) edges! */
1146  /* Hack alert, only returning ONE end of the edge right now, most do better later. */
1147  /* Hack alert #2, returning a value of 2 to indicate a co-linear crossing event. */
1148  if ( edge_contains_point(e1, &(e2->start)) )
1149  {
1150  *g = e2->start;
1151  return 2;
1152  }
1153  if ( edge_contains_point(e1, &(e2->end)) )
1154  {
1155  *g = e2->end;
1156  return 2;
1157  }
1158  if ( edge_contains_point(e2, &(e1->start)) )
1159  {
1160  *g = e1->start;
1161  return 2;
1162  }
1163  if ( edge_contains_point(e2, &(e1->end)) )
1164  {
1165  *g = e1->end;
1166  return 2;
1167  }
1168  }
1169  unit_normal(&ea, &eb, &v);
1170  LWDEBUGF(4, "v == POINT(%.12g %.12g %.12g)", v.x, v.y, v.z);
1171  g->lat = atan2(v.z, sqrt(v.x * v.x + v.y * v.y));
1172  g->lon = atan2(v.y, v.x);
1173  LWDEBUGF(4, "g == GPOINT(%.12g %.12g)", g->lat, g->lon);
1174  LWDEBUGF(4, "g == POINT(%.12g %.12g)", rad2deg(g->lon), rad2deg(g->lat));
1175  if ( edge_contains_point(e1, g) && edge_contains_point(e2, g) )
1176  {
1177  return LW_TRUE;
1178  }
1179  else
1180  {
1181  LWDEBUG(4, "flipping point to other side of sphere");
1182  g->lat = -1.0 * g->lat;
1183  g->lon = g->lon + M_PI;
1184  if ( g->lon > M_PI )
1185  {
1186  g->lon = -1.0 * (2.0 * M_PI - g->lon);
1187  }
1188  if ( edge_contains_point(e1, g) && edge_contains_point(e2, g) )
1189  {
1190  return LW_TRUE;
1191  }
1192  }
1193  return LW_FALSE;
1194 }
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:612
void normalize(POINT3D *p)
Normalize to a unit vector.
Definition: lwgeodetic.c:593
int edge_contains_point(const GEOGRAPHIC_EDGE *e, const GEOGRAPHIC_POINT *p)
Returns true if the point p is on the minor edge defined by the end points of e.
Definition: lwgeodetic.c:1012
double y
Definition: liblwgeom.h:343
#define LWDEBUG(level, msg)
Definition: lwgeom_log.h:83
double x
Definition: liblwgeom.h:343
double z
Definition: liblwgeom.h:343
void unit_normal(const POINT3D *P1, const POINT3D *P2, POINT3D *normal)
Calculates the unit normal to two vectors, trying to avoid problems with over-narrow or over-wide cas...
Definition: lwgeodetic.c:519
static double dot_product(const POINT3D *p1, const POINT3D *p2)
Convert cartesian coordinates on unit sphere to lon/lat coordinates static void cart2ll(const POINT3D...
Definition: lwgeodetic.c:424
#define LW_FALSE
Definition: liblwgeom.h:77
#define rad2deg(r)
Definition: lwgeodetic.h:80
GEOGRAPHIC_POINT start
Definition: lwgeodetic.h:63
#define LW_TRUE
Return types for functions with status returns.
Definition: liblwgeom.h:76
GEOGRAPHIC_POINT end
Definition: lwgeodetic.h:64
int geographic_point_equals(const GEOGRAPHIC_POINT *g1, const GEOGRAPHIC_POINT *g2)
Definition: lwgeodetic.c:170
#define FP_EQUALS(A, B)
#define LWDEBUGF(level, msg,...)
Definition: lwgeom_log.h:88
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