Override river mix gen layer, improve polar regions with frozen rivers, and arctic regions in the frozen oceans

src/main/java/biomesoplenty/common/world/WorldChunkManagerBOP.java

@@ -161,7 +161,7 @@ public class WorldChunkManagerBOP extends WorldChunkManager
         riversBranch = new GenLayerSmooth(1000L, riversBranch);
         
         // mix rivers into main branch
-        GenLayer riverMixFinal = new GenLayerRiverMix(100L, mainBranch, riversBranch);
+        GenLayer riverMixFinal = new GenLayerRiverMixBOP(100L, mainBranch, riversBranch);
         
         // finish biomes with Voronoi zoom
         GenLayer biomesFinal = new GenLayerVoronoiZoom(10L, riverMixFinal);

src/main/java/biomesoplenty/common/world/layer/GenLayerHeatLatitude.java

@@ -77,7 +77,13 @@ public class GenLayerHeatLatitude extends GenLayer
                         break;
                     default:
                         // ICY
-                        out[x + y * areaWidth] = ((parentVal == 0) ? BiomeGenBase.frozenOcean.biomeID : 4);
+                        // change 50% of ocean to frozen ocean, the other 50% pick random ICY biomes - too much frozen ocean is very boring
+                        if (parentVal == 0 && this.nextInt(2) == 0)
+                        {
+                            out[x + y * areaWidth] = BiomeGenBase.frozenOcean.biomeID;
+                        } else {
+                            out[x + y * areaWidth] = 4;
+                        }
                         break;
                 }
             }

src/main/java/biomesoplenty/common/world/layer/GenLayerRiverMixBOP.java

@@ -0,0 +1,75 @@
+/*******************************************************************************
+ * Copyright 2015, the Biomes O' Plenty Team
+ * 
+ * This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Public License.
+ * 
+ * To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
+ ******************************************************************************/
+
+package biomesoplenty.common.world.layer;
+
+import biomesoplenty.api.biome.BOPBiomes;
+import net.minecraft.world.biome.BiomeGenBase;
+import net.minecraft.world.gen.layer.GenLayer;
+import net.minecraft.world.gen.layer.IntCache;
+
+public class GenLayerRiverMixBOP extends GenLayer
+{
+    private GenLayer biomesBranch;
+    private GenLayer riversBranch;
+
+    public GenLayerRiverMixBOP(long seed, GenLayer biomesBranch, GenLayer riversBranch)
+    {
+        super(seed);
+        this.biomesBranch = biomesBranch;
+        this.riversBranch = riversBranch;
+    }
+
+    @Override
+    public void initWorldGenSeed(long worldSeed)
+    {
+        this.biomesBranch.initWorldGenSeed(worldSeed);
+        this.riversBranch.initWorldGenSeed(worldSeed);
+        super.initWorldGenSeed(worldSeed);
+    }
+
+    @Override
+    public int[] getInts(int areaX, int areaY, int areaWidth, int areaHeight)
+    {
+        int[] biomeIds = this.biomesBranch.getInts(areaX, areaY, areaWidth, areaHeight);
+        int[] riverValues = this.riversBranch.getInts(areaX, areaY, areaWidth, areaHeight);
+        int[] out = IntCache.getIntCache(areaWidth * areaHeight);
+
+        for (int i = 0; i < areaWidth * areaHeight; ++i)
+        {
+            if (biomeIds[i] != BiomeGenBase.frozenOcean.biomeID && biomeIds[i] != BiomeGenBase.ocean.biomeID && biomeIds[i] != BiomeGenBase.deepOcean.biomeID)
+            {
+                if (riverValues[i] == BiomeGenBase.river.biomeID)
+                {
+                    if (biomeIds[i] == BiomeGenBase.icePlains.biomeID || (BOPBiomes.arctic.isPresent() && biomeIds[i] == BOPBiomes.arctic.get().biomeID))
+                    {
+                        out[i] = BiomeGenBase.frozenRiver.biomeID;
+                    }
+                    else if (biomeIds[i] != BiomeGenBase.mushroomIsland.biomeID && biomeIds[i] != BiomeGenBase.mushroomIslandShore.biomeID)
+                    {
+                        out[i] = riverValues[i] & 255;
+                    }
+                    else
+                    {
+                        out[i] = BiomeGenBase.mushroomIslandShore.biomeID;
+                    }
+                }
+                else
+                {
+                    out[i] = biomeIds[i];
+                }
+            }
+            else
+            {
+                out[i] = biomeIds[i];
+            }
+        }
+
+        return out;
+    }
+}

src/main/java/biomesoplenty/common/world/layer/GenLayerSubBiomesBOP.java

@@ -8,6 +8,7 @@
 
 package biomesoplenty.common.world.layer;
 
+import biomesoplenty.api.biome.BOPBiomes;
 import net.minecraft.world.biome.BiomeGenBase;
 import net.minecraft.world.gen.layer.GenLayer;
 import net.minecraft.world.gen.layer.IntCache;
@@ -230,7 +231,13 @@ public class GenLayerSubBiomesBOP extends GenLayer
             }
         }
         
-        // TODO: add BOP sub biomes here
+        // BOP sub biomes from here on
+        
+        if (biomeId == BiomeGenBase.frozenOcean.biomeID && BOPBiomes.arctic.isPresent())
+        {
+            biomeId = BOPBiomes.arctic.get().biomeID;
+        }
+        
         
         return biomeId;
     }