PostGIS  2.1.10dev-r@@SVN_REVISION@@
int edge_calculate_gbox_slow ( const GEOGRAPHIC_EDGE e,
GBOX gbox 
)

Definition at line 1291 of file lwgeodetic.c.

References distance(), GEOGRAPHIC_EDGE::end, FP_EQUALS, FP_IS_ZERO, gbox_init_point3d(), gbox_merge_point3d(), geog2cart(), LW_SUCCESS, LWDEBUG, normalize(), sphere_distance(), GEOGRAPHIC_EDGE::start, POINT3D::x, GBOX::xmax, GBOX::xmin, POINT3D::y, GBOX::ymax, GBOX::ymin, POINT3D::z, GBOX::zmax, and GBOX::zmin.

1292 {
1293  int steps = 1000000;
1294  int i;
1295  double dx, dy, dz;
1296  double distance = sphere_distance(&(e->start), &(e->end));
1297  POINT3D pn, p, start, end;
1298 
1299  /* Edge is zero length, just return the naive box */
1300  if ( FP_IS_ZERO(distance) )
1301  {
1302  LWDEBUG(4, "edge is zero length. returning");
1303  geog2cart(&(e->start), &start);
1304  geog2cart(&(e->end), &end);
1305  gbox_init_point3d(&start, gbox);
1306  gbox_merge_point3d(&end, gbox);
1307  return LW_SUCCESS;
1308  }
1309 
1310  /* Edge is antipodal (one point on each side of the globe),
1311  set the box to contain the whole world and return */
1312  if ( FP_EQUALS(distance, M_PI) )
1313  {
1314  LWDEBUG(4, "edge is antipodal. setting to maximum size box, and returning");
1315  gbox->xmin = gbox->ymin = gbox->zmin = -1.0;
1316  gbox->xmax = gbox->ymax = gbox->zmax = 1.0;
1317  return LW_SUCCESS;
1318  }
1319 
1320  /* Walk along the chord between start and end incrementally,
1321  normalizing at each step. */
1322  geog2cart(&(e->start), &start);
1323  geog2cart(&(e->end), &end);
1324  dx = (end.x - start.x)/steps;
1325  dy = (end.y - start.y)/steps;
1326  dz = (end.z - start.z)/steps;
1327  p = start;
1328  gbox->xmin = gbox->xmax = p.x;
1329  gbox->ymin = gbox->ymax = p.y;
1330  gbox->zmin = gbox->zmax = p.z;
1331  for ( i = 0; i < steps; i++ )
1332  {
1333  p.x += dx;
1334  p.y += dy;
1335  p.z += dz;
1336  pn = p;
1337  normalize(&pn);
1338  gbox_merge_point3d(&pn, gbox);
1339  }
1340  return LW_SUCCESS;
1341 }
double sphere_distance(const GEOGRAPHIC_POINT *s, const GEOGRAPHIC_POINT *e)
Given two points on a unit sphere, calculate their distance apart in radians.
Definition: lwgeodetic.c:897
void normalize(POINT3D *p)
Normalize to a unit vector.
Definition: lwgeodetic.c:564
double y
Definition: liblwgeom.h:296
double xmax
Definition: liblwgeom.h:249
#define LW_SUCCESS
Definition: liblwgeom.h:55
#define LWDEBUG(level, msg)
Definition: lwgeom_log.h:50
double x
Definition: liblwgeom.h:296
int gbox_init_point3d(const POINT3D *p, GBOX *gbox)
Initialize a GBOX using the values of the point.
Definition: g_box.c:197
#define FP_IS_ZERO(A)
double z
Definition: liblwgeom.h:296
double zmax
Definition: liblwgeom.h:253
double ymin
Definition: liblwgeom.h:250
double xmin
Definition: liblwgeom.h:248
GEOGRAPHIC_POINT start
Definition: lwgeodetic.h:44
int gbox_merge_point3d(const POINT3D *p, GBOX *gbox)
Update the GBOX to be large enough to include itself and the new point.
Definition: g_box.c:186
double ymax
Definition: liblwgeom.h:251
GEOGRAPHIC_POINT end
Definition: lwgeodetic.h:45
Datum distance(PG_FUNCTION_ARGS)
void geog2cart(const GEOGRAPHIC_POINT *g, POINT3D *p)
Convert spherical coordinates to cartesion coordinates on unit sphere.
Definition: lwgeodetic.c:355
double zmin
Definition: liblwgeom.h:252
#define FP_EQUALS(A, B)

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