PostGIS  2.3.8dev-r@@SVN_REVISION@@

◆ ptarray_segmentize_sphere()

static POINTARRAY* ptarray_segmentize_sphere ( const POINTARRAY pa_in,
double  max_seg_length 

Create a new point array with no segment longer than the input segment length (expressed in radians!)

pa_in- input point array pointer
max_seg_length- maximum output segment length in radians

Definition at line 1591 of file lwgeodetic.c.

References geog2cart(), geographic_point_init(), getPoint4d_p(), LW_TRUE, lwerror(), POINTARRAY::npoints, p4d_same(), ptarray_append_point(), ptarray_construct_empty(), ptarray_has_m(), ptarray_has_z(), ptarray_segmentize_sphere_edge_recursive(), sphere_distance(), POINT4D::x, and POINT4D::y.

Referenced by lwgeom_segmentize_sphere().

1592 {
1593  POINTARRAY *pa_out;
1594  int hasz = ptarray_has_z(pa_in);
1595  int hasm = ptarray_has_m(pa_in);
1596  POINT4D p1, p2;
1597  POINT3D q1, q2;
1598  GEOGRAPHIC_POINT g1, g2;
1599  int i;
1601  /* Just crap out on crazy input */
1602  if ( ! pa_in )
1603  lwerror("%s: null input pointarray", __func__);
1604  if ( max_seg_length <= 0.0 )
1605  lwerror("%s: maximum segment length must be positive", __func__);
1607  /* Empty starting array */
1608  pa_out = ptarray_construct_empty(hasz, hasm, pa_in->npoints);
1610  /* Simple loop per edge */
1611  for (i = 1; i < pa_in->npoints; i++)
1612  {
1613  getPoint4d_p(pa_in, i-1, &p1);
1614  getPoint4d_p(pa_in, i, &p2);
1615  geographic_point_init(p1.x, p1.y, &g1);
1616  geographic_point_init(p2.x, p2.y, &g2);
1618  /* Skip duplicate points (except in case of 2-point lines!) */
1619  if ((pa_in->npoints > 2) && p4d_same(&p1, &p2))
1620  continue;
1622  /* How long is this edge? */
1623  double d = sphere_distance(&g1, &g2);
1625  if (d > max_seg_length)
1626  {
1627  geog2cart(&g1, &q1);
1628  geog2cart(&g2, &q2);
1629  /* 3-d end points, XYZM end point, current edge size, min edge size */
1630  ptarray_segmentize_sphere_edge_recursive(&q1, &q2, &p1, &p2, d, max_seg_length, pa_out);
1631  }
1632  /* If we don't segmentize, we need to add first point manually */
1633  else
1634  {
1635  ptarray_append_point(pa_out, &p1, LW_TRUE);
1636  }
1637  }
1638  /* Always add the last point */
1639  ptarray_append_point(pa_out, &p2, LW_TRUE);
1640  return pa_out;
1641 }
double x
Definition: liblwgeom.h:351
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:913
int npoints
Definition: liblwgeom.h:370
POINTARRAY * ptarray_construct_empty(char hasz, char hasm, uint32_t maxpoints)
Create a new POINTARRAY with no points.
Definition: ptarray.c:70
Point in spherical coordinates on the world.
Definition: lwgeodetic.h:47
int ptarray_append_point(POINTARRAY *pa, const POINT4D *pt, int allow_duplicates)
Append a point to the end of an existing POINTARRAY If allow_duplicate is LW_FALSE, then a duplicate point will not be added.
Definition: ptarray.c:156
#define LW_TRUE
Return types for functions with status returns.
Definition: liblwgeom.h:75
void geog2cart(const GEOGRAPHIC_POINT *g, POINT3D *p)
Convert spherical coordinates to cartesion coordinates on unit sphere.
Definition: lwgeodetic.c:369
int ptarray_has_m(const POINTARRAY *pa)
Definition: ptarray.c:43
void geographic_point_init(double lon, double lat, GEOGRAPHIC_POINT *g)
Initialize a geographic point.
Definition: lwgeodetic.c:171
int ptarray_has_z(const POINTARRAY *pa)
Definition: ptarray.c:36
double y
Definition: liblwgeom.h:351
static int ptarray_segmentize_sphere_edge_recursive(const POINT3D *p1, const POINT3D *p2, const POINT4D *v1, const POINT4D *v2, double d, double max_seg_length, POINTARRAY *pa)
Definition: lwgeodetic.c:1542
void lwerror(const char *fmt,...)
Write a notice out to the error handler.
Definition: lwutil.c:102
int getPoint4d_p(const POINTARRAY *pa, int n, POINT4D *point)
Definition: lwgeom_api.c:244
int p4d_same(const POINT4D *p1, const POINT4D *p2)
Definition: lwalgorithm.c:31
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