Index: binaries/data/mods/public/maps/random/rmgen/RandomMap.js
===================================================================
--- binaries/data/mods/public/maps/random/rmgen/RandomMap.js
+++ binaries/data/mods/public/maps/random/rmgen/RandomMap.js
@@ -16,13 +16,15 @@
 	this.IDToName = [];
 
 	// Texture 2D array
-	this.texture = [];
+	this.textureIDs = [];
+	this.texturePriorities = [];
+
 	for (let x = 0; x < this.size; ++x)
 	{
-		this.texture[x] = new Uint16Array(this.size);
-
+		this.textureIDs[x] = new Uint16Array(this.size);
+		this.texturePriorities = new Uint16Array(this.size);
 		for (let z = 0; z < this.size; ++z)
-			this.texture[x][z] = this.getTextureID(
+			this.textureIDs[x][z] = this.getTextureID(
 				typeof baseTerrain == "string" ? baseTerrain : pickRandom(baseTerrain));
 	}
 
@@ -228,7 +230,7 @@
 };
 
 /**
- * Returns the name of the texture of the given tile.
+ * Returns the name of the texture and the priority of the given tile.
  */
 RandomMap.prototype.getTexture = function(position)
 {
@@ -235,21 +237,38 @@
 	if (!this.inMapBounds(position))
 		throw new Error("getTexture: invalid tile position " + uneval(position));
 
-	return this.IDToName[this.texture[position.x][position.y]];
+	return this.IDToName[this.textureIDs[position.x][position.y]];
 };
 
 /**
- * Paints the given texture on the given tile.
+ * Paints the given texture on the given tile at the given priority.
  */
-RandomMap.prototype.setTexture = function(position, texture)
+RandomMap.prototype.setTexture = function(position, texture, priority = HIGH)
 {
 	if (position.x < 0 ||
 	    position.y < 0 ||
-	    position.x >= this.texture.length ||
-	    position.y >= this.texture[position.x].length)
+	    position.x >= this.textureIDs.length ||
+	    position.y >= this.textureIDs[position.x].length)
 		throw new Error("setTexture: invalid tile position " + uneval(position));
 
-	this.texture[position.x][position.y] = this.getTextureID(texture);
+	let [x, y] = [position.x, position.y];
+
+	// the 8 surrounding squares.
+	let surroundingTiles = [
+		this.texturePriorities[x - 1][y - 1],
+		this.texturePriorities[x][y - 1],
+		this.texturePriorities[x + 1][y - 1],
+		this.texturePriorities[x - 1][y + 1],
+		this.texturePriorities[x][y + 1],
+		this.texturePriorities[x + 1][y + 1],
+		this.texturePriorities[x - 1][y],
+		this.texturePriorities[x + 1][y]
+	];
+
+	let priorityIndex = priority == LOW ? Math.max(0, Math.min(...surroundingTiles.priority) - 1) : Math.min(65535, Math.max(...surroundingTiles.priority) + 1);
+
+	this.textureIDs[x][y] = this.getTextureID(texture);
+	this.texturePriorities[x][y] = priorityIndex;
 };
 
 RandomMap.prototype.getHeight = function(position)
@@ -463,9 +482,8 @@
 	for (let x = 0; x < this.size; ++x)
 		for (let z = 0; z < this.size; ++z)
 		{
-			// TODO: For now just use the texture's index as priority, might want to do this another way
-			tileIndex[z * this.size + x] = this.texture[x][z];
-			tilePriority[z * this.size + x] = this.texture[x][z];
+			tileIndex[z * this.size + x] = this.textureIDs[x][z];
+			tilePriority[z * this.size + x] = this.texturePriorities[x][z] || this.textureIDs[x][z];
 		}
 
 	return {
Index: binaries/data/mods/public/maps/random/rmgen/Terrain.js
===================================================================
--- binaries/data/mods/public/maps/random/rmgen/Terrain.js
+++ binaries/data/mods/public/maps/random/rmgen/Terrain.js
@@ -2,6 +2,9 @@
  * @file A Terrain is a class that modifies an arbitrary property of a given tile.
  */
 
+const LOW = 0;
+const HIGH = 1;
+
 /**
  * SimpleTerrain paints the given texture on the terrain.
  *
@@ -8,7 +11,7 @@
  * Optionally it places an entity on the affected tiles and
  * replaces prior entities added by SimpleTerrain on the same tile.
  */
-function SimpleTerrain(texture, templateName = undefined)
+function SimpleTerrain(texture, templateName = undefined, priority = HIGH)
 {
 	if (texture === undefined)
 		throw new Error("SimpleTerrain: texture not defined");
@@ -15,6 +18,7 @@
 
 	this.texture = texture;
 	this.templateName = templateName;
+	this.priority = priority;
 }
 
 SimpleTerrain.prototype.place = function(position)
@@ -22,7 +26,7 @@
 	if (this.templateName && g_Map.validTilePassable(position))
 		g_Map.setTerrainEntity(this.templateName, 0, Vector2D.add(position, new Vector2D(0.5, 0.5)), randomAngle());
 
-	g_Map.setTexture(position, this.texture);
+	g_Map.setTexture(position, this.texture, this.priority);
 };
 
 /**