triangulate.h File Reference

(Commit a65ccc9... : jennings : 2016-03-15 14:00:18 -0500)

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Classes
struct	ITRIANGLE
struct	IEDGE
struct	XYZ

Functions
int	Triangulate (int nv, XYZ *pxyz, ITRIANGLE *v, int *ntri)

Function Documentation

int Triangulate	(	int	nv,
		XYZ *	pxyz,
		ITRIANGLE *	v,
		int *	ntri
	)

Definition at line 41 of file triangulate.c.

References CircumCircle(), FALSE, ITRIANGLE::p1, IEDGE::p1, ITRIANGLE::p2, IEDGE::p2, ITRIANGLE::p3, TRUE, XYZ::x, XYZ::y, and XYZ::z.

Referenced by QxrdCenterFinder::calculateCalibration().

{
   int *complete = NULL;
   IEDGE *edges = NULL;
   int nedge = 0;
   int trimax,emax = 200;
   int status = 0;

   int inside;
   int i,j,k;
   double xp,yp,x1,y1,x2,y2,x3,y3,xc,yc,r;
   double xmin,xmax,ymin,ymax,xmid,ymid;
   double dx,dy,dmax;

   /* Allocate memory for the completeness list, flag for each triangle */
   trimax = 4 * nv;
   if ((complete = malloc(trimax*sizeof(int))) == NULL) {
      status = 1;
      goto skip;
   }

   /* Allocate memory for the edge list */
   if ((edges = malloc(emax*(long)sizeof(IEDGE))) == NULL) {
      status = 2;
      goto skip;
   }

   /*
      Find the maximum and minimum vertex bounds.
      This is to allow calculation of the bounding triangle
   */
   xmin = pxyz[0].x;
   ymin = pxyz[0].y;
   xmax = xmin;
   ymax = ymin;
   for (i=1;i<nv;i++) {
      if (pxyz[i].x < xmin) xmin = pxyz[i].x;
      if (pxyz[i].x > xmax) xmax = pxyz[i].x;
      if (pxyz[i].y < ymin) ymin = pxyz[i].y;
      if (pxyz[i].y > ymax) ymax = pxyz[i].y;
   }
   dx = xmax - xmin;
   dy = ymax - ymin;
   dmax = (dx > dy) ? dx : dy;
   xmid = (xmax + xmin) / 2.0;
   ymid = (ymax + ymin) / 2.0;

   /*
      Set up the supertriangle
      This is a triangle which encompasses all the sample points.
      The supertriangle coordinates are added to the end of the
      vertex list. The supertriangle is the first triangle in
      the triangle list.
   */
   pxyz[nv+0].x = xmid - 20 * dmax;
   pxyz[nv+0].y = ymid - dmax;
   pxyz[nv+0].z = 0.0;
   pxyz[nv+1].x = xmid;
   pxyz[nv+1].y = ymid + 20 * dmax;
   pxyz[nv+1].z = 0.0;
   pxyz[nv+2].x = xmid + 20 * dmax;
   pxyz[nv+2].y = ymid - dmax;
   pxyz[nv+2].z = 0.0;
   v[0].p1 = nv;
   v[0].p2 = nv+1;
   v[0].p3 = nv+2;
   complete[0] = FALSE;
   *ntri = 1;

   /*
      Include each point one at a time into the existing mesh
   */
   for (i=0;i<nv;i++) {

      xp = pxyz[i].x;
      yp = pxyz[i].y;
      nedge = 0;

      /*
         Set up the edge buffer.
         If the point (xp,yp) lies inside the circumcircle then the
         three edges of that triangle are added to the edge buffer
         and that triangle is removed.
      */
      for (j=0;j<(*ntri);j++) {
         if (complete[j])
            continue;
         x1 = pxyz[v[j].p1].x;
         y1 = pxyz[v[j].p1].y;
         x2 = pxyz[v[j].p2].x;
         y2 = pxyz[v[j].p2].y;
         x3 = pxyz[v[j].p3].x;
         y3 = pxyz[v[j].p3].y;
         inside = CircumCircle(xp,yp,x1,y1,x2,y2,x3,y3,&xc,&yc,&r);
         if (xc < xp && ((xp-xc)*(xp-xc)) > r)
                                complete[j] = TRUE;
         if (inside) {
            /* Check that we haven't exceeded the edge list size */
            if (nedge+3 >= emax) {
               emax += 100;
               if ((edges = realloc(edges,emax*(long)sizeof(IEDGE))) == NULL) {
                  status = 3;
                  goto skip;
               }
            }
            edges[nedge+0].p1 = v[j].p1;
            edges[nedge+0].p2 = v[j].p2;
            edges[nedge+1].p1 = v[j].p2;
            edges[nedge+1].p2 = v[j].p3;
            edges[nedge+2].p1 = v[j].p3;
            edges[nedge+2].p2 = v[j].p1;
            nedge += 3;
            v[j] = v[(*ntri)-1];
            complete[j] = complete[(*ntri)-1];
            (*ntri)--;
            j--;
         }
      }

      /*
         Tag multiple edges
         Note: if all triangles are specified anticlockwise then all
               interior edges are opposite pointing in direction.
      */
      for (j=0;j<nedge-1;j++) {
         for (k=j+1;k<nedge;k++) {
            if ((edges[j].p1 == edges[k].p2) && (edges[j].p2 == edges[k].p1)) {
               edges[j].p1 = -1;
               edges[j].p2 = -1;
               edges[k].p1 = -1;
               edges[k].p2 = -1;
            }
            /* Shouldn't need the following, see note above */
            if ((edges[j].p1 == edges[k].p1) && (edges[j].p2 == edges[k].p2)) {
               edges[j].p1 = -1;
               edges[j].p2 = -1;
               edges[k].p1 = -1;
               edges[k].p2 = -1;
            }
         }
      }

      /*
         Form new triangles for the current point
         Skipping over any tagged edges.
         All edges are arranged in clockwise order.
      */
      for (j=0;j<nedge;j++) {
         if (edges[j].p1 < 0 || edges[j].p2 < 0)
            continue;
         if ((*ntri) >= trimax) {
            status = 4;
            goto skip;
         }
         v[*ntri].p1 = edges[j].p1;
         v[*ntri].p2 = edges[j].p2;
         v[*ntri].p3 = i;
         complete[*ntri] = FALSE;
         (*ntri)++;
      }
   }

   /*
      Remove triangles with supertriangle vertices
      These are triangles which have a vertex number greater than nv
   */
   for (i=0;i<(*ntri);i++) {
      if (v[i].p1 >= nv || v[i].p2 >= nv || v[i].p3 >= nv) {
         v[i] = v[(*ntri)-1];
         (*ntri)--;
         i--;
      }
   }

skip:
   free(edges);
   free(complete);
   return(status);
}

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