PostGIS  2.5.0dev-r@@SVN_REVISION@@
int lw_dist2d_fast_ptarray_ptarray ( POINTARRAY l1,
POINTARRAY l2,
DISTPTS dl,
GBOX box1,
GBOX box2 
)

The new faster calculation comparing pointarray to another pointarray the arrays can come from both polygons and linestrings.

The naming is not good but comes from that it compares a chosen selection of the points not all of them

Definition at line 1939 of file measures.c.

References getPoint2d_cp(), lw_dist2d_pre_seg_seg(), LW_FALSE, LW_TRUE, lwalloc(), LWDEBUG, lwfree(), POINTARRAY::npoints, LISTSTRUCT::pnr, struct_cmp_by_measure(), LISTSTRUCT::themeasure, DISTPTS::twisted, POINT2D::x, GBOX::xmax, GBOX::xmin, POINT2D::y, GBOX::ymax, and GBOX::ymin.

Referenced by lw_dist2d_distribute_fast().

1940 {
1941  /*here we define two lists to hold our calculated "z"-values and the order number in the geometry*/
1942 
1943  double k, thevalue;
1944  float deltaX, deltaY, c1m, c2m;
1945  POINT2D c1, c2;
1946  const POINT2D *theP;
1947  float min1X, max1X, max1Y, min1Y,min2X, max2X, max2Y, min2Y;
1948  int t;
1949  int n1 = l1->npoints;
1950  int n2 = l2->npoints;
1951 
1952  LISTSTRUCT *list1, *list2;
1953  list1 = (LISTSTRUCT*)lwalloc(sizeof(LISTSTRUCT)*n1);
1954  list2 = (LISTSTRUCT*)lwalloc(sizeof(LISTSTRUCT)*n2);
1955 
1956  LWDEBUG(2, "lw_dist2d_fast_ptarray_ptarray is called");
1957 
1958  max1X = box1->xmax;
1959  min1X = box1->xmin;
1960  max1Y = box1->ymax;
1961  min1Y = box1->ymin;
1962  max2X = box2->xmax;
1963  min2X = box2->xmin;
1964  max2Y = box2->ymax;
1965  min2Y = box2->ymin;
1966  /*we want the center of the bboxes, and calculate the slope between the centerpoints*/
1967  c1.x = min1X + (max1X-min1X)/2;
1968  c1.y = min1Y + (max1Y-min1Y)/2;
1969  c2.x = min2X + (max2X-min2X)/2;
1970  c2.y = min2Y + (max2Y-min2Y)/2;
1971 
1972  deltaX=(c2.x-c1.x);
1973  deltaY=(c2.y-c1.y);
1974 
1975 
1976  /*Here we calculate where the line perpendicular to the center-center line crosses the axes for each vertex
1977  if the center-center line is vertical the perpendicular line will be horizontal and we find it's crossing the Y-axes with z = y-kx */
1978  if ((deltaX*deltaX)<(deltaY*deltaY)) /*North or South*/
1979  {
1980  k = -deltaX/deltaY;
1981  for (t=0; t<n1; t++) /*for each segment in L1 */
1982  {
1983  theP = getPoint2d_cp(l1, t);
1984  thevalue = theP->y - (k * theP->x);
1985  list1[t].themeasure=thevalue;
1986  list1[t].pnr=t;
1987 
1988  }
1989  for (t=0; t<n2; t++) /*for each segment in L2*/
1990  {
1991  theP = getPoint2d_cp(l2, t);
1992  thevalue = theP->y - (k * theP->x);
1993  list2[t].themeasure=thevalue;
1994  list2[t].pnr=t;
1995 
1996  }
1997  c1m = c1.y-(k*c1.x);
1998  c2m = c2.y-(k*c2.x);
1999  }
2000 
2001 
2002  /*if the center-center line is horizontal the perpendicular line will be vertical. To eliminate problems with deviding by zero we are here mirroring the coordinate-system
2003  and we find it's crossing the X-axes with z = x-(1/k)y */
2004  else /*West or East*/
2005  {
2006  k = -deltaY/deltaX;
2007  for (t=0; t<n1; t++) /*for each segment in L1 */
2008  {
2009  theP = getPoint2d_cp(l1, t);
2010  thevalue = theP->x - (k * theP->y);
2011  list1[t].themeasure=thevalue;
2012  list1[t].pnr=t;
2013  /* lwnotice("l1 %d, measure=%f",t,thevalue ); */
2014  }
2015  for (t=0; t<n2; t++) /*for each segment in L2*/
2016  {
2017  theP = getPoint2d_cp(l2, t);
2018  thevalue = theP->x - (k * theP->y);
2019  list2[t].themeasure=thevalue;
2020  list2[t].pnr=t;
2021  /* lwnotice("l2 %d, measure=%f",t,thevalue ); */
2022  }
2023  c1m = c1.x-(k*c1.y);
2024  c2m = c2.x-(k*c2.y);
2025  }
2026 
2027  /*we sort our lists by the calculated values*/
2028  qsort(list1, n1, sizeof(LISTSTRUCT), struct_cmp_by_measure);
2029  qsort(list2, n2, sizeof(LISTSTRUCT), struct_cmp_by_measure);
2030 
2031  if (c1m < c2m)
2032  {
2033  if (!lw_dist2d_pre_seg_seg(l1,l2,list1,list2,k,dl))
2034  {
2035  lwfree(list1);
2036  lwfree(list2);
2037  return LW_FALSE;
2038  }
2039  }
2040  else
2041  {
2042  dl->twisted= ((dl->twisted) * (-1));
2043  if (!lw_dist2d_pre_seg_seg(l2,l1,list2,list1,k,dl))
2044  {
2045  lwfree(list1);
2046  lwfree(list2);
2047  return LW_FALSE;
2048  }
2049  }
2050  lwfree(list1);
2051  lwfree(list2);
2052  return LW_TRUE;
2053 }
void lwfree(void *mem)
Definition: lwutil.c:244
int struct_cmp_by_measure(const void *a, const void *b)
Definition: measures.c:2056
double xmax
Definition: liblwgeom.h:292
#define LWDEBUG(level, msg)
Definition: lwgeom_log.h:83
int lw_dist2d_pre_seg_seg(POINTARRAY *l1, POINTARRAY *l2, LISTSTRUCT *list1, LISTSTRUCT *list2, double k, DISTPTS *dl)
preparation before lw_dist2d_seg_seg.
Definition: measures.c:2067
double themeasure
Definition: measures.h:58
double x
Definition: liblwgeom.h:327
double ymin
Definition: liblwgeom.h:293
double xmin
Definition: liblwgeom.h:291
#define LW_FALSE
Definition: liblwgeom.h:76
#define LW_TRUE
Return types for functions with status returns.
Definition: liblwgeom.h:75
double ymax
Definition: liblwgeom.h:294
double y
Definition: liblwgeom.h:327
int twisted
Definition: measures.h:52
void * lwalloc(size_t size)
Definition: lwutil.c:229
const POINT2D * getPoint2d_cp(const POINTARRAY *pa, uint32_t n)
Returns a POINT2D pointer into the POINTARRAY serialized_ptlist, suitable for reading from...
Definition: lwgeom_api.c:364
int pnr
Definition: measures.h:59
uint32_t npoints
Definition: liblwgeom.h:370

Here is the call graph for this function:

Here is the caller graph for this function: