PostGIS  2.5.7dev-r@@SVN_REVISION@@

## ◆ lw_dist2d_pt_arc()

 int lw_dist2d_pt_arc ( const POINT2D * P, const POINT2D * A1, const POINT2D * A2, const POINT2D * A3, DISTPTS * dl )

Definition at line 1439 of file measures.c.

1440 {
1442  POINT2D C; /* center of circle defined by arc A */
1443  POINT2D X; /* point circle(A) where line from C to P crosses */
1444
1445  if ( dl->mode < 0 )
1446  lwerror("lw_dist2d_pt_arc does not support maxdistance mode");
1447
1448  /* What if the arc is a point? */
1449  if ( lw_arc_is_pt(A1, A2, A3) )
1450  return lw_dist2d_pt_pt(P, A1, dl);
1451
1452  /* Calculate centers and radii of circles. */
1453  radius_A = lw_arc_center(A1, A2, A3, &C);
1454
1455  /* This "arc" is actually a line (A2 is colinear with A1,A3) */
1456  if ( radius_A < 0.0 )
1457  return lw_dist2d_pt_seg(P, A1, A3, dl);
1458
1459  /* Distance from point to center */
1460  d = distance2d_pt_pt(&C, P);
1461
1462  /* P is the center of the circle */
1463  if ( FP_EQUALS(d, 0.0) )
1464  {
1466  dl->p1 = *A1;
1467  dl->p2 = *P;
1468  return LW_TRUE;
1469  }
1470
1471  /* X is the point on the circle where the line from P to C crosses */
1472  X.x = C.x + (P->x - C.x) * radius_A / d;
1473  X.y = C.y + (P->y - C.y) * radius_A / d;
1474
1475  /* Is crossing point inside the arc? Or arc is actually circle? */
1476  if ( p2d_same(A1, A3) || lw_pt_in_arc(&X, A1, A2, A3) )
1477  {
1478  lw_dist2d_pt_pt(P, &X, dl);
1479  }
1480  else
1481  {
1482  /* Distance is the minimum of the distances to the arc end points */
1483  lw_dist2d_pt_pt(A1, P, dl);
1484  lw_dist2d_pt_pt(A3, P, dl);
1485  }
1486  return LW_TRUE;
1487 }
#define LW_TRUE
Return types for functions with status returns.
Definition: liblwgeom.h:76
double lw_arc_center(const POINT2D *p1, const POINT2D *p2, const POINT2D *p3, POINT2D *result)
Determines the center of the circle defined by the three given points.
Definition: lwalgorithm.c:228
#define FP_EQUALS(A, B)
int lw_arc_is_pt(const POINT2D *A1, const POINT2D *A2, const POINT2D *A3)
Returns true if arc A is actually a point (all vertices are the same) .
Definition: lwalgorithm.c:105
int lw_pt_in_arc(const POINT2D *P, const POINT2D *A1, const POINT2D *A2, const POINT2D *A3)
Returns true if P is on the same side of the plane partition defined by A1/A3 as A2 is.
Definition: lwalgorithm.c:85
int p2d_same(const POINT2D *p1, const POINT2D *p2)
Definition: lwalgorithm.c:49
void lwerror(const char *fmt,...)
Write a notice out to the error handler.
Definition: lwutil.c:190
double distance2d_pt_pt(const POINT2D *p1, const POINT2D *p2)
Definition: measures.c:2314
int lw_dist2d_pt_seg(const POINT2D *p, const POINT2D *A, const POINT2D *B, DISTPTS *dl)
lw_dist2d_comp from p to line A->B This one is now sending every occasion to lw_dist2d_pt_pt Before i...
Definition: measures.c:2206
int lw_dist2d_pt_pt(const POINT2D *thep1, const POINT2D *thep2, DISTPTS *dl)
Compares incoming points and stores the points closest to each other or most far away from each other...
Definition: measures.c:2282
POINT2D p1
Definition: measures.h:52
POINT2D p2
Definition: measures.h:53
int mode
Definition: measures.h:54
double distance
Definition: measures.h:51
double y
Definition: liblwgeom.h:331
double x
Definition: liblwgeom.h:331
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