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 n, 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.n, 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;
        if (kdt_open (kdt[nt], name)) {
  	fprintf (stderr, "terrain: could not open terrain database '%s'\n", 
  		 name);
  	exit (1);
        }
      }
      nt++;
    }
    va_end (ap);

    scalar n = new scalar;
    scalar dmin = new scalar;
    scalar dmax = new scalar;
    zb.n = 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);
    }
  }