[Freeciv-Dev] Re: PATCH: fix for smooth_map (PR#991)

[Raimar Falke <hawk@xxxxxxxxxxxxxxxxxxxxxxx>]

On Fri, Oct 05, 2001 at 12:15:26PM -0700, jdorje@xxxxxxxxxxxxxxxxxxxxx wrote:
> The following simple patch cleans up the smooth_map() function as
> discussed of freeciv-dev.
> 
> jason
> ? rc
> ? profile.sh
> Index: server/mapgen.c
> ===================================================================
> RCS file: /home/freeciv/CVS/freeciv/server/mapgen.c,v
> retrieving revision 1.72
> diff -u -r1.72 mapgen.c
> --- server/mapgen.c   2001/09/30 21:55:34     1.72
> +++ server/mapgen.c   2001/10/05 19:13:23
> @@ -31,7 +31,7 @@
>  #include "mapgen.h"
>  
>  /* Wrapper for easy access.  It's a macro so it can be a lvalue. */
> -#define hmap(x,y) (height_map[(y) * map.xsize + map_adjust_x(x)])
> +#define hmap(x,y) (height_map[map_inx(x, y)])
>  
>  static void make_huts(int number);
>  static void add_specials(int prob);
> @@ -1333,38 +1333,40 @@
>  }
>  
>  /**************************************************************************
> -  smooth_map should be viewed  as a  corrosion function on the map, it levels
> -  out the differences in the heightmap.
> +  smooth_map should be viewed  as a corrosion function on the map, it
> +  levels out the differences in the heightmap.
>  **************************************************************************/
>  static void smooth_map(void)
>  {
> -  int mx,my,px,py;
> -  int a;
> -  
> +  int* new_hmap = fc_malloc(sizeof(int) * map.xsize * map.ysize);
> +
> +  /* We make a new height map and then copy it back over the old one.
> +     Care must be taken so that the new height map uses the exact
> +     same storage structure as the real one - it must be the same
> +     size and use the same indexing.  --JDS */
> +
>    whole_map_iterate(x, y) {
> -    my = map_adjust_y(y - 1);
> -    py = map_adjust_y(y + 1);
> -    mx = map_adjust_x(x - 1);
> -    px = map_adjust_x(x + 1);
> -    a = hmap(x, y) * 2;
> -
> -    a += hmap(px, my);
> -    a += hmap(mx, my);
> -    a += hmap(mx, py);
> -    a += hmap(px, py);
> +    int a = hmap(x, y) * 2; /* double-count this tile */
> +    int dir;
>  
> -    a += hmap(x, my);
> -    a += hmap(mx, y);
> +    /* what about a new macro, adjc_nearest_iterate? */
> +    for (dir=0; dir<8; dir++) {
> +      int dx, dy, x2, y2;
> +      DIRSTEP(dx, dy, dir); /* can't use MAPSTEP */
> +      x2 = x + dx, y2 = y + dy;
> +      nearest_real_pos(&x2, &y2);

What about taking a real adjc_iterate macro and count the real tiles? 
Substitute "/10" by this count. Both methods (your patch and ignoring
un-real tiles) aren't wrong. They just differ. And we have already
changed the output of this method.

> -    a += hmap(x, py);
> -    a += hmap(px, y);
> +      a += hmap(x2, y2);
> +    }
>  
> -    a += myrand(60);
> -    a -= 30;
> +    a += myrand(60) - 30;
>      if (a < 0)
>        a = 0;
> -    hmap(x, y) = a / 10;
> +    new_hmap[map_inx(x, y)] = a / 10;
>    } whole_map_iterate_end;
> +
> +  memcpy(height_map, new_hmap, sizeof(int) * map.xsize * map.ysize);
> +  free(new_hmap);
>  }

        Raimar

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