src/terrain.h

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    #include <stdarg.h>
    #include <kdt/kdt.h>
    #pragma autolink -L$BASILISK/kdt -lkdt
    
    @if _OPENMP
    @ define NPROC omp_get_max_threads()
    @ define PROC tid()
    @else
    @ define NPROC 1
    @ define PROC 0
    @endif
    
    attribute {
      void ** kdt;
      scalar nt, dmin, dmax;
    }
    
    static int includes (KdtRect rect, Point * p)
    {
      Point point = *p;
      Delta_x /= 2.; Delta_y /= 2.;
      return (rect[0].l >= x - Delta_x && rect[0].h <= x + Delta_x &&
    	  rect[1].l >= y - Delta_y && rect[1].h <= y + Delta_y);
    }
    
    static int intersects (KdtRect rect, Point * p)
    {
      Point point = *p;
      Delta_x /= 2.; Delta_y /= 2.;
      return (rect[0].l <= x + Delta_x && rect[0].h >= x - Delta_x &&
    	  rect[1].l <= y + Delta_y && rect[1].h >= y - Delta_y);
    }
    
    static void reconstruct_terrain (Point point, scalar zb)
    {
      KdtSum s;
      kdt_sum_init (&s);
      Delta_x /= 2.; Delta_y /= 2.;
      KdtRect rect = {{x - Delta_x, x + Delta_x},
    		  {y - Delta_y, y + Delta_y}};
      for (Kdt ** kdt = (Kdt **) zb.kdt[PROC]; *kdt; kdt++)
        kdt_query_sum (*kdt,
    		   (KdtCheck) includes,
    		   (KdtCheck) intersects, &point,
    		   rect, &s);
      scalar n = zb.nt, dmin = zb.dmin, dmax = zb.dmax;
      n[] = s.n;
      if (s.w > 0.) {
        zb[] = s.H0/s.w;
        dmin[] = s.Hmin;
        dmax[] = s.Hmax;
      }
      else {
        /* not enough points in database, use bilinear interpolation
           from coarser level instead */
        if (level > 0)
          zb[] = (9.*coarse(zb,0,0) + 
    	      3.*(coarse(zb,child.x,0) + coarse(zb,0,child.y)) + 
    	      coarse(zb,child.x,child.y))/16.;
        else
          zb[] = 0.; // no points at level 0!
        dmin[] = nodata;
        dmax[] = nodata;
      }
    }
    
    void refine_terrain (Point point, scalar zb)
    {
      foreach_child()
        reconstruct_terrain (point, zb);
    }
    
    static void delete_terrain (scalar zb)
    {
      for (int i = 0; i < NPROC; i++) {
        for (Kdt ** kdt = (Kdt **) zb.kdt[i]; *kdt; kdt++)
          kdt_destroy (*kdt);
        free (zb.kdt[i]);
      }
      free (zb.kdt);
    }
    
    void terrain (scalar zb, ...)
    {
      zb.kdt = qcalloc (NPROC, void *);
      zb.delete = delete_terrain;
    
      int nt = 0;
      va_list ap;
      va_start (ap, zb);
      char * name;
      while ((name = va_arg (ap, char *))) {
        for (int i = 0; i < NPROC; i++) {
          Kdt ** kdt = (Kdt **) zb.kdt[i];
          zb.kdt[i] = qrealloc (kdt, nt + 2, Kdt *);
          kdt[nt] = kdt_new();
          kdt[nt + 1] = NULL;
          char * fname = name;
          if (name[0] == '~') {
    	char * home = getenv ("HOME");
    	if (home != NULL) {
    	  fname = malloc(sizeof(char)*(strlen(home) + strlen(name)));
    	  strcpy (fname, home);
    	  strcat (fname, name + 1);
    	}
          }
          if (kdt_open (kdt[nt], fname)) {	
    	fprintf (stderr, "terrain: could not open terrain database '%s'\n", 
    		 fname);
    	exit (1);
          }
          if (fname != name)
    	free (fname);
        }
        nt++;
      }
      va_end (ap);
    
      scalar n = new scalar;
      scalar dmin = new scalar;
      scalar dmax = new scalar;
      zb.nt = n;
      zb.dmin = dmin;
      zb.dmax = dmax;
    
    #if TREE
      zb.refine = refine_terrain;
      n.refine = no_restriction;
      n.restriction = no_restriction;
      dmin.refine = no_restriction;
      dmin.restriction = no_restriction;
      dmax.refine = no_restriction;
      dmax.restriction = no_restriction;
    #endif
    
      trash ({zb});
      for (int l = 0; l <= depth(); l++) {
        foreach_level (l)
          reconstruct_terrain (point, zb);
        boundary_level ({zb}, l);
      }
    }