Dungeon-Building Algorithm

(Originally written by Mike Anderson. Please note that this guide only contains the essential parts about the algorithm, nothing else from his guide)

In this algorithm a "feature" is taken to mean any kind of map component e.g. large room, small room, corridor, circular arena, vault etc.

1. Fill the whole map with solid earth

2. Dig out a single room in the centre of the map

3. Pick a wall of any room

4. Decide upon a new feature to build

5. See if there is room to add the new feature through the chosen wall

6. If yes, continue. If no, go back to step 3

7. Add the feature through the chosen wall

8. Go back to step 3, until the dungeon is complete

9. Add the up and down staircases at random points in map

10. Finally, sprinkle some monsters and items liberally over dungeon

Step 1 and 2 are easy once you've got the map set up. I have found it very useful to write a "fillRect" command that fills a rectangular map area with a specified tile type.

Step 3 is trickier. You can't pick random squares to add new features because the rule is to always add to the existing dungeon. This makes the connections look good, and also guarantees that every square is reachable. The way Tyrant does it is to pick random squares on the map until it finds a wall square adjacent (horizontally or vertically) to a clear square. This is a good method, since it gives you a roughly even chance of picking any particular wall square.

Step 4 isn't too hard - I just use a random switch statement to determine which of a range of features to build. You can change the whole look of the map by weighting the probabilities of different features. Well-ordered dungeons will have lots of regular rooms and long straight corridors. Cave complexes will tend to have jagged caverns, twisting passages etc.

Step 5 is more tricky, and the key to the whole algorithm. For each feature, you need to know the area of the map that it will occupy. Then you need to scan outwards from the chosen wall to see if this area intersects any features that are already there. Tyrant does this in a fairly simplistic way - it just works out the rectangular space that the new feature will occupy plus a square on each side for walls, then checks to see if the entire rectangle is currently filled with solid earth.

Step 6 decides whether or not to add the feature. If the area under consideration contains anything other than solid earth already, then the routine loops back to step 3. Note that *most* new features will be rejected in this way. This isn't a problem, as the processing time is negligible. Tyrant tries to add 300 or so features to each dungeon, but usually only 40 or so make it past this stage.

Step 7 draws the new feature once you've decided the area is OK. In this stage, you can also add any interesting room features, such as inhabitants, traps, secret doors and treasure.

Step 8 just loops back to build more rooms. The exact number of times that you want to do this will depend on map size and various other factors.

Step 9 is pretty self-explanatory. Easiest way to do it is to write a routine that picks random squares until it finds an empty one where the staircases can be added.

Step 10 just creates a host of extra random monsters in random locations to add some spice. Tyrant creates about most of the monsters at this point of the map generation, although it does add a few special creatures when individual rooms are generated.

Java example

(Made by Solarnus)

import java.lang.Integer; //so we can use Integer.parseInt()

import java.util.*; //and for getting today's date



public class dungen{
	//max size of the map

	private int xmax = 80; //80 columns

	private int ymax = 25; //25 rows



	//size of the map

	private int xsize = 0;

	private int ysize = 0;

	

	//number of "objects" to generate on the map

	private int objects = 0;

	

	//define the %chance to generate either a room or a corridor on the map
	//BTW, rooms are 1st priority so actually it's enough to just define the chance
	//of generating a room

	private int chanceRoom = 75; 

	private int chanceCorridor = 25;



	//our map

	private int[] dungeon_map = new int[0];

	

	//the old seed from the RNG is saved in this one

	private long oldseed = 0;

	

	//a list over tile types we're using

	final private int tileUnused = 0;

	final private int tileDirtWall = 1; //not in use

	final private int tileDirtFloor = 2;

	final private int tileStoneWall = 3;

	final private int tileCorridor = 4;

	final private int tileDoor = 5;

	final private int tileUpStairs = 6;

	final private int tileDownStairs = 7;

	final private int tileChest = 8;

	

	//misc. messages to print

	private String msgXSize = "X size of dungeon: \t";

	private String msgYSize = "Y size of dungeon: \t";

	private String msgMaxObjects = "max # of objects: \t";

	private String msgNumObjects = "# of objects made: \t";

	private String msgHelp = "";

	private String msgDetailedHelp = "";




	//setting a tile's type

	private void setCell(int x, int y, int celltype){

		dungeon_map[x + xsize * y] = celltype;

	}

	

	//returns the type of a tile

	private int getCell(int x, int y){

		return dungeon_map[x + xsize * y];

	}

	

	//The RNG. the seed is based on seconds from the "java epoch" ( I think..)
	//perhaps it's the same date as the unix epoch

	private int getRand(int min, int max){

		//the seed is based on current date and the old, already used seed
		Date now = new Date();

		long seed = now.getTime() + oldseed;

		oldseed = seed;

		

		Random randomizer = new Random(seed);

		int n = max - min + 1;

		int i = randomizer.nextInt() % n;

		if (i < 0)

			i = -i;

		//System.out.println("seed: " + seed + "\tnum:  " + (min + i));

		return min + i;

	}

	

	private boolean makeCorridor(int x, int y, int lenght, int direction){

		//define the dimensions of the corridor (er.. only the width and height..)

		int len = getRand(2, lenght);

		int floor = tileCorridor;

		int dir = 0;

		if (direction > 0 && direction < 4) dir = direction;

		
		int xtemp = 0;

		int ytemp = 0;

		

		switch(dir){

		case 0:

		//north

			//check if there's enough space for the corridor
			//start with checking it's not out of the boundaries

			if (x < 0 || x > xsize) return false;

			else xtemp = x;

			
			//same thing here, to make sure it's not out of the boundaries

			for (ytemp = y; ytemp > (y-len); ytemp--){

				if (ytemp < 0 || ytemp > ysize) return false; //oh boho, it was!

				if (getCell(xtemp, ytemp) != tileUnused) return false;

			}

			

			//if we're still here, let's start building

			for (ytemp = y; ytemp > (y-len); ytemp--){

				setCell(xtemp, ytemp, floor);

			}

			break;

		case 1:

		//east

				if (y < 0 || y > ysize) return false;

				else ytemp = y;

				

				for (xtemp = x; xtemp < (x+len); xtemp++){

					if (xtemp < 0 || xtemp > xsize) return false;

					if (getCell(xtemp, ytemp) != tileUnused) return false;

				}

				

				for (xtemp = x; xtemp < (x+len); xtemp++){

					setCell(xtemp, ytemp, floor);

				}

			break;

		case 2:

		//south

			if (x < 0 || x > xsize) return false;

			else xtemp = x;

			

			for (ytemp = y; ytemp < (y+len); ytemp++){

				if (ytemp < 0 || ytemp > ysize) return false;

				if (getCell(xtemp, ytemp) != tileUnused) return false;

			}

			

			for (ytemp = y; ytemp < (y+len); ytemp++){

				setCell(xtemp, ytemp, floor);

			}

			break;

		case 3:

		//west

			if (ytemp < 0 || ytemp > ysize) return false;

			else ytemp = y;

			

			for (xtemp = x; xtemp > (x-len); xtemp--){

				if (xtemp < 0 || xtemp > xsize) return false;

				if (getCell(xtemp, ytemp) != tileUnused) return false; 

			}

		

			for (xtemp = x; xtemp > (x-len); xtemp--){

				setCell(xtemp, ytemp, floor);

			}

			break;

		}

		

		//woot, we're still here! let's tell the other guys we're done!!

		return true;

	}

	

	private boolean makeRoom(int x, int y, int xlength, int ylength, int direction){

		//define the dimensions of the room, it should be at least 4x4 tiles (2x2 for walking on, the rest is walls)

		int xlen = getRand(4, xlength);

		int ylen = getRand(4, ylength);

		//the tile type it's going to be filled with

		int floor = tileDirtFloor; //jordgolv..

		int wall = tileDirtWall; //jordv?¤gg

		//choose the way it's pointing at

		int dir = 0;

		if (direction > 0 && direction < 4) dir = direction;



		switch(dir){

		case 0:

		//north

			//Check if there's enough space left for it

			for (int ytemp = y; ytemp > (y-ylen); ytemp--){

				if (ytemp < 0 || ytemp > ysize) return false;

				for (int xtemp = (x-xlen/2); xtemp < (x+(xlen+1)/2); xtemp++){

					if (xtemp < 0 || xtemp > xsize) return false;

					if (getCell(xtemp, ytemp) != tileUnused) return false; //no space left...

				}

			}

			

			//we're still here, build

			for (int ytemp = y; ytemp > (y-ylen); ytemp--){

				for (int xtemp = (x-xlen/2); xtemp < (x+(xlen+1)/2); xtemp++){

					//start with the walls

					if (xtemp == (x-xlen/2)) setCell(xtemp, ytemp, wall);

					else if (xtemp == (x+(xlen-1)/2)) setCell(xtemp, ytemp, wall);

					else if (ytemp == y) setCell(xtemp, ytemp, wall);

					else if (ytemp == (y-ylen+1)) setCell(xtemp, ytemp, wall);

					//and then fill with the floor

					else setCell(xtemp, ytemp, floor);

				}

			}

			break;

		case 1:

		//east

			for (int ytemp = (y-ylen/2); ytemp < (y+(ylen+1)/2); ytemp++){

				if (ytemp < 0 || ytemp > ysize) return false;

				for (int xtemp = x; xtemp < (x+xlen); xtemp++){

					if (xtemp < 0 || xtemp > xsize) return false;

					if (getCell(xtemp, ytemp) != tileUnused) return false;

				}

			}



			for (int ytemp = (y-ylen/2); ytemp < (y+(ylen+1)/2); ytemp++){

				for (int xtemp = x; xtemp < (x+xlen); xtemp++){

					

					if (xtemp == x) setCell(xtemp, ytemp, wall);

					else if (xtemp == (x+xlen-1)) setCell(xtemp, ytemp, wall);

					else if (ytemp == (y-ylen/2)) setCell(xtemp, ytemp, wall);

					else if (ytemp == (y+(ylen-1)/2)) setCell(xtemp, ytemp, wall);

					

					else setCell(xtemp, ytemp, floor);

				}

			}

			break;

		case 2:

		//south

			for (int ytemp = y; ytemp < (y+ylen); ytemp++){

				if (ytemp < 0 || ytemp > ysize) return false;

				for (int xtemp = (x-xlen/2); xtemp < (x+(xlen+1)/2); xtemp++){

					if (xtemp < 0 || xtemp > xsize) return false;

					if (getCell(xtemp, ytemp) != tileUnused) return false;

				}

			}

			

			for (int ytemp = y; ytemp < (y+ylen); ytemp++){

				for (int xtemp = (x-xlen/2); xtemp < (x+(xlen+1)/2); xtemp++){

					

					if (xtemp == (x-xlen/2)) setCell(xtemp, ytemp, wall);

					else if (xtemp == (x+(xlen-1)/2)) setCell(xtemp, ytemp, wall);

					else if (ytemp == y) setCell(xtemp, ytemp, wall);

					else if (ytemp == (y+ylen-1)) setCell(xtemp, ytemp, wall);

					

					else setCell(xtemp, ytemp, floor);

				}

			}

			break;

		case 3:

		//west

			for (int ytemp = (y-ylen/2); ytemp < (y+(ylen+1)/2); ytemp++){

				if (ytemp < 0 || ytemp > ysize) return false;

				for (int xtemp = x; xtemp > (x-xlen); xtemp--){

					if (xtemp < 0 || xtemp > xsize) return false;

					if (getCell(xtemp, ytemp) != tileUnused) return false; 

				}

			}

			

			for (int ytemp = (y-ylen/2); ytemp < (y+(ylen+1)/2); ytemp++){

				for (int xtemp = x; xtemp > (x-xlen); xtemp--){

					

					if (xtemp == x) setCell(xtemp, ytemp, wall);

					else if (xtemp == (x-xlen+1)) setCell(xtemp, ytemp, wall);

					else if (ytemp == (y-ylen/2)) setCell(xtemp, ytemp, wall);

					else if (ytemp == (y+(ylen-1)/2)) setCell(xtemp, ytemp, wall);

					

					else setCell(xtemp, ytemp, floor);

				}

			}

			break;

		}

		

		//yay, all done

		return true;

	}

	

	

	//used to print the map on the screen

	public void showDungeon(){

		for (int y = 0; y < ysize; y++){

			for (int x = 0; x < xsize; x++){

				//System.out.print(getCell(x, y));

				switch(getCell(x, y)){

				case tileUnused:

					System.out.print(" ");

					break;

				case tileDirtWall:

					System.out.print("+");

					break;

				case tileDirtFloor:

					System.out.print(".");

					break;

				case tileStoneWall:

					System.out.print("O");

					break;

				case tileCorridor:

					System.out.print("#");

					break;

				case tileDoor:

					System.out.print("D");

					break;

				case tileUpStairs:

					System.out.print("<");

					break;

				case tileDownStairs:

					System.out.print(">");

					break;

				case tileChest:

					System.out.print("*");

					break;

				};

			}

			if (xsize < xmax) System.out.print("\n");

		}

	}

	

	//and here's the one generating the whole map

	public boolean createDungeon(int inx, int iny, int inobj){

		if (inobj < 1) objects = 10;

		else objects = inobj;

		

		//justera kartans storlek, om den ?¤r st?¶rre eller mindre ?¤n "gr?¤nserna"
		//adjust the size of the map, if it's smaller or bigger than the limits

		if (inx < 3) xsize = 3;

		else if (inx > xmax) xsize = xmax;

		else xsize = inx;

		

		if (iny < 3) ysize = 3;

		else if (iny > ymax) ysize = ymax;

		else ysize = iny;

		

		System.out.println(msgXSize + xsize);

		System.out.println(msgYSize + ysize);

		System.out.println(msgMaxObjects + objects);

		

		//redefine the map var, so it's adjusted to our new map size

		dungeon_map = new int[xsize * ysize];

		

		//start with making the "standard stuff" on the map

		for (int y = 0; y < ysize; y++){

			for (int x = 0; x < xsize; x++){

				//ie, making the borders of unwalkable walls

				if (y == 0) setCell(x, y, tileStoneWall);

				else if (y == ysize-1) setCell(x, y, tileStoneWall);

				else if (x == 0) setCell(x, y, tileStoneWall);

				else if (x == xsize-1) setCell(x, y, tileStoneWall);

				

				//and fill the rest with dirt

				else setCell(x, y, tileUnused);

			}

		}

		

		/*******************************************************************************

		And now the code of the random-map-generation-algorithm begins!

		*******************************************************************************/

		

		//start with making a room in the middle, which we can start building upon

		makeRoom(xsize/2, ysize/2, 8, 6, getRand(0,3)); //getrand saken f?¶r att slumpa fram riktning p?? rummet

		

		//keep count of the number of "objects" we've made

		int currentFeatures = 1; //+1 for the first room we just made

		

		//then we sart the main loop

		for (int countingTries = 0; countingTries < 1000; countingTries++){

			//check if we've reached our quota

			if (currentFeatures == objects){

				break;

			}

				

			//start with a random wall

			int newx = 0;

			int xmod = 0;

			int newy = 0;

			int ymod = 0;

			int validTile = -1;

			//1000 chances to find a suitable object (room or corridor)..
			//(yea, i know it's kinda ugly with a for-loop... -_-')

			for (int testing = 0; testing < 1000; testing++){

				newx = getRand(1, xsize-1);

				newy = getRand(1, ysize-1);

				validTile = -1;

				//System.out.println("tempx: " + newx + "\ttempy: " + newy);

				if (getCell(newx, newy) == tileDirtWall || getCell(newx, newy) == tileCorridor){

					//check if we can reach the place

					if (getCell(newx, newy+1) == tileDirtFloor || getCell(newx, newy+1) == tileCorridor){

						validTile = 0; //

						xmod = 0;

						ymod = -1;

					}

					else if (getCell(newx-1, newy) == tileDirtFloor || getCell(newx-1, newy) == tileCorridor){

						validTile = 1; //

						xmod = +1;

						ymod = 0;

					}

					else if (getCell(newx, newy-1) == tileDirtFloor || getCell(newx, newy-1) == tileCorridor){

						validTile = 2; //

						xmod = 0;

						ymod = +1;

					}

					else if (getCell(newx+1, newy) == tileDirtFloor || getCell(newx+1, newy) == tileCorridor){

						validTile = 3; //

						xmod = -1;

						ymod = 0;

					}

					

					//check that we haven't got another door nearby, so we won't get alot of openings besides
					//each other

					if (validTile > -1){

						if (getCell(newx, newy+1) == tileDoor) //north

							validTile = -1;

						else if (getCell(newx-1, newy) == tileDoor)//east

							validTile = -1;

						else if (getCell(newx, newy-1) == tileDoor)//south

							validTile = -1;

						else if (getCell(newx+1, newy) == tileDoor)//west

							validTile = -1;

					}

					

					//if we can, jump out of the loop and continue with the rest

					if (validTile > -1) break;

				}

			}

			if (validTile > -1){

				//choose what to build now at our newly found place, and at what direction

				int feature = getRand(0, 100);

				if (feature <= chanceRoom){ //a new room

					if (makeRoom((newx+xmod), (newy+ymod), 8, 6, validTile)){

						currentFeatures++; //add to our quota

						

						//then we mark the wall opening with a door

						setCell(newx, newy, tileDoor);

						

						//clean up infront of the door so we can reach it

						setCell((newx+xmod), (newy+ymod), tileDirtFloor);

					}

				}

				else if (feature >= chanceRoom){ //new corridor

					if (makeCorridor((newx+xmod), (newy+ymod), 6, validTile)){

						//same thing here, add to the quota and a door

						currentFeatures++;

						

						setCell(newx, newy, tileDoor);

					}

				}

			}

		}

		

		

		/*******************************************************************************

		All done with the building, let's finish this one off

		*******************************************************************************/

		

		//sprinkle out the bonusstuff (stairs, chests etc.) over the map

		int newx = 0;

		int newy = 0;

		int ways = 0; //from how many directions we can reach the random spot from

		int state = 0; //the state the loop is in, start with the stairs

		while (state != 10){

			for (int testing = 0; testing < 1000; testing++){

				newx = getRand(1, xsize-1);

				newy = getRand(1, ysize-2); //cheap bugfix, pulls down newy to 0<y<24, from 0<y<25



				//System.out.println("x: " + newx + "\ty: " + newy);

				ways = 4; //the lower the better

				

				//check if we can reach the spot

				if (getCell(newx, newy+1) == tileDirtFloor || getCell(newx, newy+1) == tileCorridor){

				//north

					if (getCell(newx, newy+1) != tileDoor)

					ways--;

				}

				if (getCell(newx-1, newy) == tileDirtFloor || getCell(newx-1, newy) == tileCorridor){

				//east

					if (getCell(newx-1, newy) != tileDoor)

					ways--;

				}

				if (getCell(newx, newy-1) == tileDirtFloor || getCell(newx, newy-1) == tileCorridor){

				//south

					if (getCell(newx, newy-1) != tileDoor)

					ways--;

				}

				if (getCell(newx+1, newy) == tileDirtFloor || getCell(newx+1, newy) == tileCorridor){

				//west

					if (getCell(newx+1, newy) != tileDoor)

					ways--;

				}

				

				if (state == 0){

					if (ways == 0){

					//we're in state 0, let's place a "upstairs" thing

						setCell(newx, newy, tileUpStairs);

						state = 1;

						break;

					}

				}

				else if (state == 1){

					if (ways == 0){

					//state 1, place a "downstairs"

						setCell(newx, newy, tileDownStairs);

						state = 10;

						break;

					}

				}

			}

		}

		

		

		//all done with the map generation, tell the user about it and finish

		System.out.println(msgNumObjects + currentFeatures);

		

		return true;

	}



////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

	

	public static void main(String[] args){

		//initial stuff used in making the map

		int x = 80; int y = 25; int dungeon_objects = 0;

		

		//convert a string to a int, if there's more then one arg

		if (args.length >= 1)

			dungeon_objects = Integer.parseInt(args[0]);



		if (args.length >= 2)

			x = Integer.parseInt(args[1]);

		

		if (args.length >= 3)

			y = Integer.parseInt(args[2]);



		//create a new class of "dungen", so we can use all the goodies within it

		dungen generator = new dungen();

		

		//then we create a new dungeon map

		if (generator.createDungeon(x, y, dungeon_objects)){

			//always good to be able to see the results..

			generator.showDungeon();

		}

	}

}