src/main/java/StevenDimDoors/experimental/MazeGenerator.java

@@ -1,5 +1,7 @@
 package StevenDimDoors.experimental;
 
+import java.util.ArrayList;
+import java.util.Collections;
 import java.util.Random;
 
 import net.minecraft.block.Block;
@@ -13,18 +15,60 @@ public class MazeGenerator
 {
 	public static final int ROOT_WIDTH = 40;
 	public static final int ROOT_LENGTH = 40;
-	public static final int ROOT_HEIGHT = 19;
+	public static final int ROOT_HEIGHT = 20;
 	private static final int MIN_HEIGHT = 4;
 	private static final int MIN_SIDE = 3;
-	private static final int SPLIT_COUNT = 8;
+	private static final int SPLIT_COUNT = 9;
 	
 	private MazeGenerator() { }
 	
 	public static void generate(World world, int x, int y, int z, Random random)
 	{
 		SpatialNode root = partitionRooms(ROOT_WIDTH, ROOT_HEIGHT, ROOT_LENGTH, SPLIT_COUNT, random);
+		// Collect all the leaf nodes by performing a tree traversal
+		ArrayList<SpatialNode> rooms = new ArrayList<SpatialNode>(1 << SPLIT_COUNT);
+		listRooms(root, rooms);
+		removeRandomRooms(rooms, random);
 		buildRooms(root, world, new Point3D(x - ROOT_WIDTH / 2, y - ROOT_HEIGHT - 1, z - ROOT_WIDTH / 2));
+	}
 	
+	private static void listRooms(SpatialNode node, ArrayList<SpatialNode> rooms)
+	{
+		if (node.isLeaf())
+		{
+			rooms.add(node);
+		}
+		else
+		{
+			listRooms(node.leftChild(), rooms);
+			listRooms(node.rightChild(), rooms);
+		}
+	}
+		
+	private static void removeRandomRooms(ArrayList<SpatialNode> rooms, Random random)
+	{
+		// Randomly remove a fraction of the rooms
+		Collections.shuffle(rooms, random);
+		int remaining = rooms.size() / 2;
+		for (int k = rooms.size() - 1; k >= remaining; k--)
+		{
+			removeRoom(rooms.remove(k));
+		}
+	}
+	
+	private static void removeRoom(SpatialNode node)
+	{
+		// Remove a node and any of its ancestors that become leaf nodes
+		SpatialNode parent;
+		SpatialNode current;
+		
+		current = node;
+		while (current != null && current.isLeaf())
+		{
+			parent = current.parent();
+			current.remove();
+			current = parent;
+		}
 	}
 	
 	private static SpatialNode partitionRooms(int width, int height, int length, int maxLevels, Random random)
@@ -99,7 +143,9 @@ public class MazeGenerator
 		}
 		else
 		{
+			if (node.leftChild() != null)
 				buildRooms(node.leftChild(), world, offset);
+			if (node.rightChild() != null)
 				buildRooms(node.rightChild(), world, offset);
 		}
 	}

src/main/java/StevenDimDoors/experimental/SpatialNode.java

@@ -6,17 +6,20 @@ public class SpatialNode
 {
 	private Point3D minCorner;
 	private Point3D maxCorner;
+	private SpatialNode parent;
 	private SpatialNode leftChild = null;
 	private SpatialNode rightChild = null;
 	
 	public SpatialNode(int width, int height, int length)
 	{
+		parent = null;
 		minCorner = new Point3D(0, 0, 0);
 		maxCorner = new Point3D(width - 1, height - 1, length - 1);
 	}
 	
-	private SpatialNode(Point3D minCorner, Point3D maxCorner)
+	private SpatialNode(SpatialNode parent, Point3D minCorner, Point3D maxCorner)
 	{
+		this.parent = parent;
 		this.minCorner = minCorner;
 		this.maxCorner = maxCorner;
 	}
@@ -38,7 +41,7 @@ public class SpatialNode
 	
 	public boolean isLeaf()
 	{
-		return (leftChild == null);
+		return (leftChild == null && rightChild == null);
 	}
 	
 	public SpatialNode leftChild()
@@ -61,9 +64,14 @@ public class SpatialNode
 		return maxCorner;
 	}
 	
+	public SpatialNode parent()
+	{
+		return parent;
+	}
+	
 	public void splitByX(int rightStart)
 	{
-		if (leftChild != null)
+		if (!this.isLeaf())
 		{
 			throw new IllegalStateException("This node has already been split.");
 		}
@@ -71,13 +79,13 @@ public class SpatialNode
 		{
 			throw new IllegalArgumentException("The specified cutting plane is invalid.");
 		}
-		leftChild = new SpatialNode(minCorner, new Point3D(rightStart - 1, maxCorner.getY(), maxCorner.getZ()));
-		rightChild = new SpatialNode(new Point3D(rightStart, minCorner.getY(), minCorner.getZ()), maxCorner);
+		leftChild = new SpatialNode(this, minCorner, new Point3D(rightStart - 1, maxCorner.getY(), maxCorner.getZ()));
+		rightChild = new SpatialNode(this, new Point3D(rightStart, minCorner.getY(), minCorner.getZ()), maxCorner);
 	}
 	
 	public void splitByY(int rightStart)
 	{
-		if (leftChild != null)
+		if (!this.isLeaf())
 		{
 			throw new IllegalStateException("This node has already been split.");
 		}
@@ -85,13 +93,13 @@ public class SpatialNode
 		{
 			throw new IllegalArgumentException("The specified cutting plane is invalid.");
 		}
-		leftChild = new SpatialNode(minCorner, new Point3D(maxCorner.getX(), rightStart - 1, maxCorner.getZ()));
-		rightChild = new SpatialNode(new Point3D(minCorner.getX(), rightStart, minCorner.getZ()), maxCorner);
+		leftChild = new SpatialNode(this, minCorner, new Point3D(maxCorner.getX(), rightStart - 1, maxCorner.getZ()));
+		rightChild = new SpatialNode(this, new Point3D(minCorner.getX(), rightStart, minCorner.getZ()), maxCorner);
 	}
 	
 	public void splitByZ(int rightStart)
 	{
-		if (leftChild != null)
+		if (!this.isLeaf())
 		{
 			throw new IllegalStateException("This node has already been split.");
 		}
@@ -99,7 +107,19 @@ public class SpatialNode
 		{
 			throw new IllegalArgumentException("The specified cutting plane is invalid.");
 		}
-		leftChild = new SpatialNode(minCorner, new Point3D(maxCorner.getX(), maxCorner.getY(), rightStart - 1));
-		rightChild = new SpatialNode(new Point3D(minCorner.getX(), minCorner.getY(), rightStart), maxCorner);
+		leftChild = new SpatialNode(this, minCorner, new Point3D(maxCorner.getX(), maxCorner.getY(), rightStart - 1));
+		rightChild = new SpatialNode(this, new Point3D(minCorner.getX(), minCorner.getY(), rightStart), maxCorner);
+	}
+	
+	public void remove()
+	{
+		if (parent != null)
+		{
+			if (parent.leftChild == this)
+				parent.leftChild = null;
+			else
+				parent.rightChild = null;
+			parent = null;
+		}
 	}
 }