[Freeciv-Dev] (PR#12806) idea: harsh climate generator

["Brian Dunstan" <bdunstan149@xxxxxxxxx>]

<URL: http://bugs.freeciv.org/Ticket/Display.html?id=12806 >

I have noticed that even with extreme settings e.g.
temperature=0, you do not get extreme results with the
terrain generator.  I am sure this is by design, but
some users may want to create an ice planet, or desert
planet, perhaps for a scenario.

The attached patch adds a setting (under 'rare'),
harshclimate, that will take the climate settings
literally.  Literally meaning, no hills when steepness
is zero, no deserts when wetness is 100, etc.

Also: I have noticed that sometimes the river
generator will move a river from a non-hill square
(e.g. jungle), to a hill sqare, and then off again. 
This seems to defy common sense.  I think it is
because the height map views the river as moving from
a high-elevation jungle, to a lower elevation hill, to
still lower elevation.  It still looks very odd
however.  I am wondering if this behavior is unwelcome
(i.e. should I bother making a patch for it)




                
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diff -Nur -Xfreeciv/diff_ignore freeciv/common/map.h 
freeciv_altered/common/map.h
--- freeciv/common/map.h        2005-04-15 10:33:38.364027920 -0400
+++ freeciv_altered/common/map.h        2005-04-15 13:38:53.221312776 -0400
@@ -109,6 +109,7 @@
   bool tinyisles;
   bool separatepoles;
   bool alltemperate;
+  bool harshclimate;
   int temperature;
   int wetness;
   int steepness;
@@ -594,6 +595,10 @@
 #define MAP_MIN_ALLTEMPERATE       FALSE
 #define MAP_MAX_ALLTEMPERATE       TRUE
 
+#define MAP_DEFAULT_HARSHCLIMATE   FALSE
+#define MAP_MIN_HARSHCLIMATE       FALSE
+#define MAP_MAX_HARSHCLIMATE       TRUE
+
 #define MAP_DEFAULT_TEMPERATURE   50
 #define MAP_MIN_TEMPERATURE       0
 #define MAP_MAX_TEMPERATURE       100
diff -Nur -Xfreeciv/diff_ignore freeciv/server/generator/mapgen.c 
freeciv_altered/server/generator/mapgen.c
--- freeciv/server/generator/mapgen.c   2005-04-15 10:33:38.185055128 -0400
+++ freeciv_altered/server/generator/mapgen.c   2005-04-15 14:40:22.576445544 
-0400
@@ -190,6 +190,12 @@
                                int thill, int my_height)
 {
   int higher_than_me = 0;
+
+  /* Harsh climate: when steepness is set very low, it's ok to get
+   * unending flatlands. */
+  if(map.harshclimate &&
+     map.steepness <= 15) return FALSE;
+
   square_iterate(ptile, 2, tile1) {
     if (hmap(tile1) > thill) {
       return FALSE;
@@ -213,13 +219,19 @@
 
 /**************************************************************************
   we don't want huge areas of hill/mountains, 
-  so we put in a plains here and there, where it gets too 'heigh' 
+  so we put in a plains here and there, where it gets too 'high' 
 
   Return TRUE if the terrain at the given map position is too heigh.
 ****************************************************************************/
 static bool terrain_is_too_high(struct tile *ptile,
                                int thill, int my_height)
 {
+
+  /* Harsh climate -- when steepness is set very high, it's ok to get
+   *  unending mountains.  */
+  if(map.harshclimate &&
+     map.steepness >= 85) return FALSE;
+
   square_iterate(ptile, 1, tile1) {
     if (hmap(tile1) + (hmap_max_level - hmap_mountain_level) / 5 < thill) {
       return FALSE;
@@ -357,10 +369,24 @@
   } else if (tmap_is(ptile, TT_COLD)) {
     map_set_terrain(ptile, T_TUNDRA); 
   } else {
-    if (myrand(100) > 50) {
-      map_set_terrain(ptile, T_GRASSLAND);
-    } else {
-      map_set_terrain(ptile, T_PLAINS);
+
+    /* Harsh climate: do not place grasslands on dry maps.
+     * Do not place plains on wet maps. */
+    if(map.harshclimate) {
+      if(myrand(99) < map.wetness) {
+       map_set_terrain(ptile, T_GRASSLAND);
+      }
+      else {
+       map_set_terrain(ptile, T_PLAINS);
+      }
+    }  
+    /* Normal climate: random choice between plains, grassland */
+    else {
+      if (myrand(100) > 50) {
+       map_set_terrain(ptile, T_GRASSLAND);
+      } else {
+       map_set_terrain(ptile, T_PLAINS);
+      }
     }
   }
   map_set_placed(ptile);
@@ -1142,20 +1168,58 @@
 
   mountain_pct = factor * map.steepness * 90;
 
-  /* 27 % if wetness == 50 & */
-  forest_pct = factor * (map.wetness * 40 + 700) ; 
-  jungle_pct = forest_pct * (MAX_COLATITUDE - TROPICAL_LEVEL) /
-               (MAX_COLATITUDE * 2);
-  forest_pct -= jungle_pct;
-
-  /* 3 - 11 % */
-  river_pct = (100 - polar) * (3 + map.wetness / 12) / 100;
-
-  /* 6 %  if wetness == 50 && temperature == 50 */
-  swamp_pct = factor * MAX(0, 
-                          (map.wetness * 9 - 150 + map.temperature * 6));
-  desert_pct =factor * MAX(0,
-               (map.temperature * 15 - 250 + (100 - map.wetness) * 10)) ;
+  /* Harsh climate: use literal meaning of wetness, dryness,
+   * steepness settings.  No deserts on wet planets, no
+   * swamps on dry ones, no jungles on frozen ones */
+  if(map.harshclimate) {
+
+    int remaining = 0;
+
+    /* this must be done to prevent errors later on */
+    int t = MIN(map.temperature, 99);
+    
+#define SQR(x) ((x)*(x))
+    
+    river_pct = SQR(map.wetness) / SQR(100); 
+    remaining = 100 - mountain_pct;
+    
+    /* forests: prefer terrain steep or wet */
+    forest_pct = (map.steepness + map.wetness)/2;
+    forest_pct = (remaining*forest_pct)/100;
+    remaining -= forest_pct;
+
+    /* jungles: prefer terrain hot, and either wet or steep */
+    jungle_pct = (forest_pct * SQR(t)) / SQR(100);
+    forest_pct -= jungle_pct;
+
+    /* deserts: prefer terrain hot and dry */
+    desert_pct = (t*(100-map.wetness) * remaining) / SQR(100);
+    remaining -= desert_pct;
+
+    /* swamp: prefer terrain hot, wet, and flat */
+    swamp_pct = (map.wetness * (100 - map.steepness) * remaining) / SQR(100);
+    remaining -= swamp_pct;
+    
+#undef SQR
+  }
+  else {
+
+    forest_pct = factor * (map.wetness * 40 + 700) ; 
+    jungle_pct = forest_pct * (MAX_COLATITUDE - TROPICAL_LEVEL) /
+      (MAX_COLATITUDE * 2);
+    forest_pct -= jungle_pct;
+    
+    
+    river_pct = (100 - polar) * (3 + map.wetness / 12) / 100;
+    
+    
+  swamp_pct = 
+    factor * MAX(0, (map.wetness * 9 - 150 + map.temperature * 6));
+  desert_pct =
+    factor * MAX(0, (map.temperature * 15 - 250 + (100 - map.wetness) * 10));
+
+  }
+
 }
 
 /****************************************************************************
diff -Nur -Xfreeciv/diff_ignore freeciv/server/generator/temperature_map.c 
freeciv_altered/server/generator/temperature_map.c
--- freeciv/server/generator/temperature_map.c  2005-04-15 10:33:38.172057104 
-0400
+++ freeciv_altered/server/generator/temperature_map.c  2005-04-15 
15:05:32.000978136 -0400
@@ -85,6 +85,21 @@
   
      /* the base temperature is equal to base map_colatitude */
     int t = map_colatitude(ptile);
+
+    /* harsh climate: to the extent temperature differs from 50, 
+     * expand influence of very low planet temperatures to the equator,
+     * and the influence of very high planet temperature to the poles */
+    if(map.harshclimate) {
+#define SQR(x) ((x)*(x))
+      int planetary_temperature = (map.temperature * MAX_COLATITUDE)/100;
+      int harshness = SQR(100-2*map.temperature);
+      int mildness = SQR(100) - harshness;
+
+      t += ((harshness * planetary_temperature) + (mildness * t)) / 
+       (2*SQR(100));
+#undef SQR
+    }
+
     if (!real) {
       tmap(ptile) = t;
     } else {
@@ -95,15 +110,16 @@
       float temperate = 0.15 * (map.temperature / 100 - t / MAX_COLATITUDE) * 
          2 * MIN (50 ,count_ocean_near_tile(ptile, FALSE, TRUE)) /
          100;
-      
-      tmap(ptile) =  t * (1.0 + temperate) * (1.0 + height);
+
+      tmap(ptile) =  t * (1.0 + temperate) * (1.0 + height);      
     }
   } whole_map_iterate_end;
   /* adjust to get well sizes frequencies */
   /* Notice: if colatitude is load from a scenario never call adjust has
              scenario maybe has a odd colatitude ditribution and adjust will
             brack it */
-  if (!map.alltemperate) {
+  if (!map.alltemperate
+      && !map.harshclimate) {
     adjust_int_map(temperature_map, MAX_COLATITUDE);
   }
   /* now simplify to 4 base values */ 
@@ -119,5 +135,5 @@
     } else {
       temperature_map[i] = TT_FROZEN;
     }
-  } 
+  }
 }
diff -Nur -Xfreeciv/diff_ignore freeciv/server/settings.c 
freeciv_altered/server/settings.c
--- freeciv/server/settings.c   2005-04-15 10:33:38.105067288 -0400
+++ freeciv_altered/server/settings.c   2005-04-15 13:38:53.225312168 -0400
@@ -293,6 +293,18 @@
           N_("0 = normal Earth-like planet; 1 = all-temperate planet "),
           NULL, MAP_DEFAULT_ALLTEMPERATE)
 
+  GEN_BOOL("harshclimate", map.harshclimate, 
+          SSET_MAP_GEN, SSET_GEOLOGY, SSET_RARE, SSET_TO_CLIENT,
+          N_("Allows extreme climates"),
+          N_("Applies climate settings literally.  For example, "
+             "steepness=0 indicates that there are no hills or "
+             "mountains.  Wetness=0 will mean the planet is mostly "
+             "desert, with no swamps, forests, or jungles.  Setting "
+             "temperature=0 will lead to a planet almost completely "
+             "composed of arctic and tundra.\n"
+             "0 - standard climate.  1 - allow climate extremes"),
+          NULL, MAP_DEFAULT_HARSHCLIMATE)
+
   GEN_INT("temperature", map.temperature,
          SSET_MAP_GEN, SSET_GEOLOGY, SSET_SITUATIONAL, SSET_TO_CLIENT,
          N_("Average temperature of the planet"),