Geografic-Information-System/vector/v.voronoi/sw_voronoi.c

#include <stdlib.h>
#include <grass/gis.h>
#include "sw_defs.h"

/* implicit parameters: nsites, sqrt_nsites, xmin, xmax, ymin, ymax,
   deltax, deltay (can all be estimates).
   Performance suffers if they are wrong; better to make nsites,
   deltax, and deltay too big than too small.  (?) */

int voronoi(struct Site *(*nextsite) (void))
{
    struct Site *newsite, *bot, *top, *temp, *p;
    struct Site *v;
    struct Point newintstar;
    int pm;
    struct Halfedge *lbnd, *rbnd, *llbnd, *rrbnd, *bisector;
    struct Edge *e;
    int counter = 0;

    PQinitialize();
    bottomsite = (*nextsite) ();
    ELinitialize();

    newsite = (*nextsite) ();
    while (1) {
	if (!PQempty())
	    newintstar = PQ_min();

	if (newsite != (struct Site *)NULL && 
	    (PQempty() || newsite->coord.y < newintstar.y || 
	    (newsite->coord.y == newintstar.y && 
	    newsite->coord.x < newintstar.x))) {	/* new site is smallest */

	    G_percent(counter++, nsites, 2);

	    lbnd = ELleftbnd(&(newsite->coord));
	    rbnd = ELright(lbnd);
	    bot = rightreg(lbnd);
	    e = bisect(bot, newsite);
	    bisector = HEcreate(e, le);
	    ELinsert(lbnd, bisector);
	    if ((p = intersect(lbnd, bisector)) != (struct Site *)NULL) {
		PQdelete(lbnd);
		PQinsert(lbnd, p, dist(p, newsite));
	    }
	    lbnd = bisector;
	    bisector = HEcreate(e, re);
	    ELinsert(lbnd, bisector);
	    if ((p = intersect(bisector, rbnd)) != (struct Site *)NULL) {
		PQinsert(bisector, p, dist(p, newsite));
	    }
	    /* get next site, but ensure that it doesn't have the same
	       coordinates as the previous. If so, step over to the following
	       site. Andrea Aime 4/7/2001 */
	    do
		temp = (*nextsite) ();
	    while (temp != (struct Site *)NULL &&
		   temp->coord.x == newsite->coord.x &&
		   temp->coord.y == newsite->coord.y);
	    newsite = temp;
	}
	else if (!PQempty()) {
	    /* intersection is smallest */
	    lbnd = PQextractmin();
	    llbnd = ELleft(lbnd);
	    rbnd = ELright(lbnd);
	    rrbnd = ELright(rbnd);
	    bot = leftreg(lbnd);
	    top = rightreg(rbnd);

	    v = lbnd->vertex;
	    makevertex(v);
	    endpoint(lbnd->ELedge, lbnd->ELpm, v);
	    endpoint(rbnd->ELedge, rbnd->ELpm, v);
	    ELdelete(lbnd);
	    PQdelete(rbnd);
	    ELdelete(rbnd);
	    pm = le;
	    if (bot->coord.y > top->coord.y) {
		temp = bot;
		bot = top;
		top = temp;
		pm = re;
	    }
	    e = bisect(bot, top);
	    bisector = HEcreate(e, pm);
	    ELinsert(llbnd, bisector);
	    endpoint(e, re - pm, v);
	    deref(v);
	    if ((p = intersect(llbnd, bisector)) != (struct Site *)NULL) {
		PQdelete(llbnd);
		PQinsert(llbnd, p, dist(p, bot));
	    }
	    if ((p = intersect(bisector, rrbnd)) != (struct Site *)NULL) {
		PQinsert(bisector, p, dist(p, bot));
	    }
	}
	else
	    break;
    }

    G_percent(1, 1, 1);

    return 0;
}