PostGIS  2.5.1dev-r@@SVN_REVISION@@

◆ lwt_GetFaceByPoint()

LWT_ELEMID lwt_GetFaceByPoint ( LWT_TOPOLOGY topo,
LWPOINT pt,
double  tol 
)

Find the face-id of a face containing a given point.

Parameters
topothe topology to operate on
pointthe point to use for query
tolmax distance around the given point to look for a containing face
Returns
a face identifier if one is found (0 if universe), -1 on error (multiple faces within distance or point on node or edge). The liblwgeom error handler will be invoked in case of error.

Definition at line 4718 of file lwgeom_topo.c.

References _lwt_release_edges(), LWT_TOPOLOGY_T::be_iface, LWT_ISO_EDGE::edge_id, LWT_ISO_EDGE::face_left, LWT_ISO_EDGE::face_right, LWT_ISO_EDGE::geom, LWDEBUG, LWDEBUGF, lwerror(), lwgeom_mindistance2d_tolerance(), lwline_as_lwgeom(), lwnotice(), lwpoint_as_lwgeom(), lwt_be_getEdgeWithinDistance2D(), lwt_be_getFaceContainingPoint(), lwt_be_lastErrorMessage(), LWT_COL_EDGE_EDGE_ID, LWT_COL_EDGE_FACE_LEFT, LWT_COL_EDGE_FACE_RIGHT, LWT_COL_EDGE_GEOM, and LWTFMT_ELEMID.

4719 {
4720  LWT_ELEMID id = 0;
4721  LWT_ISO_EDGE *elem;
4722  int num, i;
4723  int flds = LWT_COL_EDGE_EDGE_ID |
4727  LWGEOM *qp = lwpoint_as_lwgeom(pt);
4728 
4729  id = lwt_be_getFaceContainingPoint(topo, pt);
4730  if ( id == -2 ) {
4731  lwerror("Backend error: %s", lwt_be_lastErrorMessage(topo->be_iface));
4732  return -1;
4733  }
4734 
4735  if ( id > 0 )
4736  {
4737  return id;
4738  }
4739  id = 0; /* or it'll be -1 for not found */
4740 
4741  LWDEBUG(1, "No face properly contains query point,"
4742  " looking for edges");
4743 
4744  /* Not in a face, may be in universe or on edge, let's check
4745  * for distance */
4746  /* NOTE: we never pass a tolerance of 0 to avoid ever using
4747  * ST_Within, which doesn't include endpoints matches */
4748  elem = lwt_be_getEdgeWithinDistance2D(topo, pt, tol?tol:1e-5, &num, flds, 0);
4749  if ( num == -1 )
4750  {
4751  lwerror("Backend error: %s", lwt_be_lastErrorMessage(topo->be_iface));
4752  return -1;
4753  }
4754  for (i=0; i<num; ++i)
4755  {
4756  LWT_ISO_EDGE *e = &(elem[i]);
4757  LWT_ELEMID eface = 0;
4758  LWGEOM* geom;
4759  double dist;
4760 
4761  if ( ! e->geom )
4762  {
4763  _lwt_release_edges(elem, num);
4764  lwnotice("Corrupted topology: edge %" LWTFMT_ELEMID
4765  " has null geometry", e->edge_id);
4766  continue;
4767  }
4768 
4769  /* don't consider dangling edges */
4770  if ( e->face_left == e->face_right )
4771  {
4772  LWDEBUGF(1, "Edge %" LWTFMT_ELEMID
4773  " is dangling, won't consider it", e->edge_id);
4774  continue;
4775  }
4776 
4777  geom = lwline_as_lwgeom(e->geom);
4778  dist = lwgeom_mindistance2d_tolerance(geom, qp, tol);
4779 
4780  LWDEBUGF(1, "Distance from edge %" LWTFMT_ELEMID
4781  " is %g (tol=%g)", e->edge_id, dist, tol);
4782 
4783  /* we won't consider edges too far */
4784  if ( dist > tol ) continue;
4785  if ( e->face_left == 0 ) {
4786  eface = e->face_right;
4787  }
4788  else if ( e->face_right == 0 ) {
4789  eface = e->face_left;
4790  }
4791  else {
4792  _lwt_release_edges(elem, num);
4793  lwerror("Two or more faces found");
4794  return -1;
4795  }
4796 
4797  if ( id && id != eface )
4798  {
4799  _lwt_release_edges(elem, num);
4800  lwerror("Two or more faces found"
4801 #if 0 /* debugging */
4802  " (%" LWTFMT_ELEMID
4803  " and %" LWTFMT_ELEMID ")", id, eface
4804 #endif
4805  );
4806  return -1;
4807  }
4808  else id = eface;
4809  }
4810  if ( num ) _lwt_release_edges(elem, num);
4811 
4812  return id;
4813 }
LWT_ELEMID face_left
#define LWT_COL_EDGE_FACE_LEFT
void lwnotice(const char *fmt,...)
Write a notice out to the notice handler.
Definition: lwutil.c:177
double lwgeom_mindistance2d_tolerance(const LWGEOM *lw1, const LWGEOM *lw2, double tolerance)
Function handling min distance calculations and dwithin calculations.
Definition: measures.c:213
#define LWT_COL_EDGE_FACE_RIGHT
LWLINE * geom
#define LWDEBUG(level, msg)
Definition: lwgeom_log.h:83
LWGEOM * lwline_as_lwgeom(const LWLINE *obj)
Definition: lwgeom.c:330
const LWT_BE_IFACE * be_iface
LWT_ELEMID face_right
LWT_ELEMID edge_id
#define LWT_COL_EDGE_EDGE_ID
Edge fields.
static void _lwt_release_edges(LWT_ISO_EDGE *edges, int num_edges)
Definition: lwgeom_topo.c:457
LWT_ISO_EDGE * lwt_be_getEdgeWithinDistance2D(LWT_TOPOLOGY *topo, LWPOINT *pt, double dist, int *numelems, int fields, int limit)
Definition: lwgeom_topo.c:260
LWGEOM * lwpoint_as_lwgeom(const LWPOINT *obj)
Definition: lwgeom.c:335
LWT_INT64 LWT_ELEMID
Identifier of topology element.
#define LWT_COL_EDGE_GEOM
#define LWDEBUGF(level, msg,...)
Definition: lwgeom_log.h:88
LWT_ELEMID lwt_be_getFaceContainingPoint(LWT_TOPOLOGY *topo, LWPOINT *pt)
Definition: lwgeom_topo.c:330
const char * lwt_be_lastErrorMessage(const LWT_BE_IFACE *be)
Definition: lwgeom_topo.c:120
void lwerror(const char *fmt,...)
Write a notice out to the error handler.
Definition: lwutil.c:190
#define LWTFMT_ELEMID
Definition: lwgeom_topo.c:44
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