Last time we improved our engine to let us make nice clean 90 degree turns, a definite requirement of any proper dungeon crawler. The next logical step is to let us also move forward in whatever direction we happen to be facing so that we can actually explore our 3D maze instead of just admiring it from one spot.

The logic for moving forward is very similar for the logic of making a 90 degree turn.

1. Wait for the user to press the up key
2. Enter a “moving” state that blocks new player input
3. For every frame spent moving move the player a small distance in the direction they are facing
4. Once the user has moved an entire dungeon square distance reset their state and wait for the next key press

The only tricky bit here is keeping track of which direction the player needs to move in. With turning we could always just add (or subtract) 90 degrees from our current position and trust things would work out fine. But with movement sometimes we will need to add to the player’s x position and sometimes to their z position.

Obviously we need some way to keep track of which axis the player should move along when they press the move key. While we could technically calculate this information based off of the player’s current degree of rotation I think it makes for easier and cleaner code to just explicitly keep track of whether the player is facing north, east, south or west. And of course that means we’re going to need new constants and a new player variable.

const NORTH = 100;
const EAST = 101;
const WEST = 102;
const SOUTH = 103;

var direction = NORTH;

And then to keep track of our actual movement we’re going to need a few more:

const MOVING_FORWARD = 4;

var walkDistance = 0;
var startX = 0;
var startZ = 0;

Now let’s put those to work, first by updating our turning code to also properly update the direction the player is facing. Because the player is locked into a full turn as soon as they press the key we might as well do things the easy way and update their direction as soon as they press left or right; no need to wait until the end of the turn. So find the if statements inside of the waiting state and add to them like so:

if(playerInput.left){
   state = TURNING_LEFT;
   switch(direction){
      case NORTH:
         direction = WEST;
         break;
      case EAST:
         direction = NORTH;
         break;
      case SOUTH:
         direction = EAST;
         break;
      case WEST:
         direction = SOUTH;
         break;
   }
}
else if(playerInput.right){
   state = TURNING_RIGHT;
   switch(direction){
      case NORTH:
         direction = EAST;
         break;
      case EAST:
         direction = SOUTH;
         break;
      case SOUTH:
         direction = WEST;
         break;
      case WEST:
         direction = NORTH;
         break;
   }
 }

Now that we know what direction the player is facing we can safely move them forward. To start let’s add some detection code for the up key inside of our waiting state block. This else if should go immediately after the playerInput.right else if we just updated:

else if(playerInput.up){
   walkingDistance = 0;
   startX = camera.position.x;
   startZ = camera.position.z;
   state = MOVING_FORWARD;
}

Pretty simple. If the player presses the up button we put them in the MOVING_FORWARD state and initialize the data we need to make the move succeed. In particular we need to mark down where the player is currently standing in startX and startZ. We also reset the walkingDistance variable to 0 since we’re going to need to use that data to figure out when we should stop moving.

Of course, being in the MOVING_FORWARD state doesn’t do us any good unless there is code for it. So make some space at the end of your render function, right before the recursive call to render, and add this:

if(state == MOVING_FORWARD)
{
   walkingDistance += 1 /30;

   if(walkingDistance >= 1){
      walkingDistance = 1;
      state = WAITING;
   }

   switch(direction){
      case NORTH:
         camera.position.z = startZ - walkingDistance;
         break;
      case EAST:
         camera.position.x = startX + walkingDistance;
         break;
      case SOUTH:
         camera.position.z = startZ + walkingDistance;
         break;
      case WEST:
         camera.position.x = startX - walkingDistance;
         break;
   }
}

This logic should look familiar since it’s just our 90 degree turn code straightened into a line.

Basically for every frame we spend MOVING_FORWARD we extend our walking distance by a fraction of a square length (which for us is 1). We then look at our current direction to figure out which way we need to move and update the camera to a new position based off our starting location and the distance we have moved so far. As walkingDistance increases the camera gets moved farther and farther from where it started.

When walking distance exceeds 1 whole unit we force it back to a perfect 1 and reset our state to waiting for input. By not including a return statement we also get to have one final round of camera updates based off of the perfect 1 which should properly place the camera at the desired end point, ready for any future turns or moves. This is important because missing our target by even a tiny fraction can add up over the course of several hundred moves and leave the camera in the completely wrong place.

If everything went well you can now load your code and walk around our tiny three square maze. Of course, the lack of any sort of collision detection also means you can ghost through the walls and walk right out of the maze but solving that is a problem for another day.

Still, we have a little bit of time left over so let’s make a quick improvement to the code.

At the moment our turn and move code both move the player a set amount per frame. This is an OK approach, especially since the requestAnimationFrame function we’re using does its best to maintain a constant 60 or so frames per second.

But that frame rate is not guaranteed! If your game is really complicated or the user has too many tabs open that frame rate can start to drop and a quick turn that was supposed to take a single second can drag on and on and on.

Alternatively changes in computer technology might lead to a much higher frame rate and suddenly that carefully planned one second turn flashes by in half that time.

Even pro games have issues like this. For example, Dark Souls 2 originally ran at 30 frames per second and calculated weapon durability based on that fact. When it got ported to a new generation of faster machines they boosted the frame rate to 60 and suddenly all the weapons were breaking half twice as fast. Woops.

The solution to these problems is to, whenever possible, base game calculations not off of frames but off of actual time passed. That way you can program game events to take exactly one second regardless of whether that second lasts for thirty frames or three frames or three hundred frames.

First off we’re going to need a variable to keep track of what time it is. Let’s toss it up by the rest of our contsants and global variables:

var last_update = Date.now();

It’s default value is whatever time it is when the program gets initialized.

Now near the top of our render function we can add:

var now = Date.now();

var deltaTime = now - last_update;
last_update = now;

These three lines get the current time and compare it to our last stored time in order to figure out how long our last frame lasted. We then reset our update time so we can start counting our next frame.

Now if we want to turn once per second we can:

turningArc += Math.PI/2 * deltaTime/1000;

And if we want to walk forward one square in one second:

walkingDistance += 1 * deltaTime/1000;

We are now frame-rate independent!

If we want to actually control our dungeon experience of just spinning around in automated circles the first thing we’re going to need is a way to get user input. Fortunately we already know how to do that in javascript.

For those of you who don’t feel like reading the linked article we basically create a global javascript object that stores what buttons are currently being pushed. We then create a pair of functions, one designed to keep track of keys being pushed and one to keep track of keys being released. Finally we link those two functions to the webpages natural keyDown and keyUp events.

In other words, put this somewhere convenient, like at the top of your script before the runMaze function:

var playerInput = new Object();

function doKeyDown(event){
   var keynum;

   if(window.event){ //Browser is IE
      keynum = event.keyCode;
   }
   else{
      keynum = event.which;
   }

   if(keynum == 37){
      playerInput.left = 1;
   }
   else if(keynum == 38){
      playerInput.up = 1;
   }
   else if(keynum == 39){
      playerInput.right = 1;
   }
   else if(keynum == 40){
      playerInput.down = 1;
   }
}

function doKeyUp(event){
   var keynum;
   
   if(window.event){ //Browser is IE
      keynum = event.keyCode;
   }
   else{
      keynum = event.which;
   }

   if(keynum == 37){
      playerInput.left = 0;
   }
   else if(keynum == 38){
      playerInput.up = 0;
   }
   else if(keynum == 39){
      playerInput.right = 0;
   }
   else if(keynum == 40){
      playerInput.down = 0;
   }
}

Then be sure to update your body definition like so:

<body onload="runMaze();" onkeydown="doKeyDown(event);" onkeyup="doKeyUp(event);">

And voila! We can now track the arrow keys. Let’s see if we can do anything cool with that.

For instance, what if we were to wrap our automatic camera rotation code inside of an if statement?

var render = function () {
   requestAnimationFrame( render );

   if(playerInput.left){
      camera.rotation.y += 0.01;
   }
   else if(playerInput.right){
      camera.rotation.y -= 0.01;
   }

   renderer.render(scene, camera);
};

And now we can spin the camera IN BOTH DIRECTIONS by holding down the left and right arrows.

Wrong Genre?

Of course, if you’ve played a dungeon crawler before you might notice that something here doesn’t feel quite right. Specifically, we shouldn’t be able to turn just a few degrees at a time. It’s much more traditional to lock the player to the four cardinal directions and force them to slowly rotate through a full 90 degrees on each keypress.

Ironically limiting the player’s control like this is actually going to be harder than just letting them do whatever they want. No more directly reacting to button presses on each frame. Instead we need a multi-step workflow like this:

1) Put the player into a TURNING state that blocks new input

2) While TURNING rotate the player a few degrees per frame

3) When the player has turned a full 90 degrees remove the TURNING state and wait for more input

That means we’re going to need some constants (which Javascript finally sort-of supports) to list out our possible states and a variable for keeping track of which state the player is currently in.

const WAITING = 1;
const TURNING_RIGHT = 2;
const TURNING_LEFT = 3;

var state = WAITING;

We’re also going to want to keep track of which way the camera is currently pointing as well as how far the player has already turned.

var currentDirection = 0;
var turningArc = 0;

With all that we can now setup our loop to start managing state for us by putting this in our render function.

if(state == WAITING){
   if(playerInput.left){
      state = TURNING_LEFT;
   }
   else if(playerInput.right){
      state = TURNING_RIGHT;
   }
}

And now we can use that state to slowly (over the course of 60 frames) move the player through a 90 degree (half PI radian) arc by getting rid of our old turning code and replacing it with something like this:

if(state == TURNING_LEFT){
   turningArc += Math.PI/2 / 60;
   if(turningArc >= Math.PI/2){
      turningArc = Math.PI/2;
      currentDirection = currentDirection + turningArc;
      turningArc = 0;
      state = WAITING;
   }
   
   camera.rotation.y = currentDirection + turningArc;
}

if(state == TURNING_RIGHT){
   turningArc += Math.PI/2 / 60;
   if(turningArc >= Math.PI/2){
      turningArc = Math.PI/2;
      currentDirection = currentDirection - turningArc;
      turningArc = 0;
      state = WAITING;
   }

   camera.rotation.y = currentDirection - turningArc;
}

Now when we are TURNING_LEFT (or RIGHT) we start each frame by adding one 60^th of a turn to our turningArc. We then adjust the camera by setting its y rotation to the combination of our turningArc to our currentDirection. So if the player is facing north (0 radians) and has turned 30 degrees the camera will point North-North East.

We also check whether or not we’ve turned a full 90 degrees. When we have that means the turn is finished and several things happen:

1) We set our turningArc to exactly 90 degrees to avoid overshooting out goal. We don’t want the player accidentally turning 91 degrees or eventually they’ll be pointing in the completely wrong direction.

2) We update our currentDirection to reflect the completed turn.

3) We reset the turningArc so it’s ready for our next turn

4) We change the state to waiting so the game will accept input again

Really the only strange thing here is the fact that we have to ADD turning angles when turning left and SUBTRACT them when turning right, which seems backwards. This is just because of the orientation of the default y axis of our engine. If you really cared I’m sure you can swap it around by turning the game’s main camera completely upside down before moving the player or building any walls but I’m just going to live with it.

Time To Move On

We have a nice basic framework for turning around now, but it’s hard to call this a dungeon crawler while the player is stuck in just one place. The next obvious step is to add some actual movement through some code pretty similar to what we just wrote. Sadly there’s no quite enough room to include that all right here so I guess I’ll see you next time!

We’ve seen how to use three.js to manually create and position walls within our labyrinth. But building a full size maze by hand would be be boring, easy to mess up and hard to maintain.

Let’s not do that.

Instead let’s write a bunch of helper code to do the heavy lifting for us.

For starters I’d like a function to help put walls in the right place, a function that would let us forget about doing math and instead just say something like “I want a north wall at maze location <3, 5>”.

Not a particularly hard thing to write either. First we calculate the center point of the maze location we want to put the wall at. Since all of our walls are a convenient 1 unit wide that’s as simple as directly assigning our maze coordinates to our wall coordinates. The only trick here is that by default in 3D space the y axis points straight up so what we call the “y coordinate” in 2D space is actually the  “z coordinate” in 3D space. (Well… unless you want to rotate the camera around a bunch but let’s not bother with that).

Once we have the x and z coordinates of the center of our maze location we next have to check whether the wall is supposed to be to the north, east, south or west. We then rotate the wall and push it half a unit away from the center. Be sure to double check this step; it’s pretty easy to accidentally mix things up so that east walls wind up getting pushed to the west or get rotated backwards and basically disappear (since walls are one-sided).

function placeWall(x,y,direction){
   var wall = new THREE.Mesh( wallGeometry, wallMaterial );
   wall.position.z = y;
   wall.position.x = x;

   if(direction == 'n'){
      wall.position.z -= 0.5;
   }
   else if(direction == 'e'){
      wall.position.x += 0.5;
      wall.rotation.y = -Math.PI/2;
   }
   else if(direction == 's'){
      wall.position.z += 0.5;
      wall.rotation.y = Math.PI;
   }
   else if(direction == 'w'){
      wall.position.x -= 0.5;
      wall.rotation.y = Math.PI/2;
   }
   else{
      return false;
   }

   scene.add(wall);
}

Now we can replace all of our wall positioning code with:

placeWall(0,0,'n');
placeWall(0,0,'e');
placeWall(0,0,'w');
placeWall(0,0,'s');

And everything looks the same as before.

Which is boring. Replace that with this:

placeWall(0,0,'n');
placeWall(0,0,'w');
placeWall(0,0,'s');
placeWall(1,0,'n');
placeWall(1,0,'e');
placeWall(1,0,'s');

And now we get a hallway that’s twice as wide as our original square room.

If only remodeling in real life was so easy…

I Thought You Had The Map…

Our new helper function makes it almost impossible to mess up when placing a wall. But there’s still a couple problems:

1) It’s kind of hard to remember where we have and haven’t placed walls

2) For an interactive maze it’s not enough to just place the walls, we need to keep track of where they are for later navigation.

So what we really need is a way to describe our entire maze all at once and all in one place. We can then use that maze data to build the 3D graphics and then also use it later on for keeping track of where the player is in the maze and how they can and can’t move.

So what is the most convenient way to define our high level maze data?

Well… a maze is fundamentally just a grid of connected cells that may or may not have walls between them. So we can think of a maze as a two dimensional array of cell objects and we can define a cell object as a set of four wall values that are either “true” (there is a wall) or “false” (there is no wall).

Now since a cell has 4 walls it basically contains 4 bits of information. This means we could define each cell as a single 4-bit super-short integer and then use bitwise logic to calculate…

JUST KIDDING!

Modern computers have billions of bytes of memory. Since our program is unlikely to ever have more than a few hundred cells there is absolutely no need to obsess about jamming as much information into as few bits as possible. Instead we can write our code in a way that’s easy for us humans to understand and work with.

Something like this:

function MazeCell(northWall, eastWall, southWall, westWall){
   this.northWall = northWall;
   this.eastWall = eastWall;
   this.southWall = southWall;
   this.westWall = westWall;
}

Then we can define new cells in our labyrinth as easily as:

var cell = new MazeCell(true, true, false, true);

Of course, we don’t want our cells just hanging out in random variables. We want them to be part of a nice big grid array, something more like this:

var mazeGrid = [Array(2), Array(2)];
mazeGrid[0][0] = new MazeCell(true, false, false, true);
mazeGrid[0][1] = new MazeCell(true, true, true, false);
mazeGrid[1][0] = new MazeCell(false, true, true, true);
mazeGrid[1][1] = new MazeCell(false,false,false,false);

Which works out to be a simple ‘L” shaped room. (That’s why the last room has no walls, it’s completely blocked off from the rest of the maze and doesn’t really matter because it can’t be seen.)

Bringing It All Together

Now we have some maze data AND a function that can accurately drop walls down wherever we want. Mix them together and we can build an entire maze!

All we need is a nested foreach loop. The first loop will grab the rows from the maze. Then for each row we’ll have a second loop that grabs each individual cell and builds whatever walls it needs.

mazeGrid.forEach(function(mazeRow, rowCount){
   mazeRow.forEach(function(mazeCell, colCount){
      if(mazeCell.northWall)
         placeWall(colCount, rowCount, 'n');
      if(mazeCell.eastWall)
         placeWall(colCount, rowCount, 'e');
      if(mazeCell.southWall)
         placeWall(colCount, rowCount, 's');
      if(mazeCell.westWall)
         placeWall(colCount, rowCount, 'w');
   });
});

And now we can use our automatically rotating camera to see the shape of our little “L” shaped room.

OK… but where are we going to find a carpet that shape?

Of course there’s a limit to how much use we can get out of an automatically rotating camera. If the maze gets even a little bit bigger we wont be able to see the whole thing from our starting point at <0, 0>. If only we could control the camera, maybe walk around the maze like an actual dungeon crawler.

Hey! I’ve got a great idea for the next update!

Last time we started our adventure into building a 3D labyrinth by putting up a single wall, and while that was pretty neat the truth is it barely qualifies as a road block, much less a maze.

So let’s pop up another three walls and at least make ourselves a room.

Since all of our walls are the exact same shape and color (for now, at least) we can save on both code and memory by reusing the same geometry and material again and again. (Note: pro games do this too. If there are 100 identical orcs on the screen odds are good they’re all being drawn based off a single in-memory model).

While all of our walls will be sharing the same 3D data they will still have their own unique position data, which should make sense since we want all all the walls to be in difference places.

For example, let’s put a wall to the left of our camera (which lives at position <0,0,0>). To put a wall to the left of of the camera’s position we need to leave the z and y coordinates alone but set the x position to -0.5. We will then also need to twist the wall 90 degrees so that it sits at a right angle with our other wall. Well, I say 90 degrees but three.js uses radians so make that half a Pi instead. Translated into code:

var wall2 = new THREE.Mesh( wallGeometry, wallMaterial)
 wall2.position.x = -0.5;
 wall2.rotation.y = Math.PI/2;
 scene.add( wall2 );

The only trick here is making sure you twist the wall in the right direction. Since we are using a one sided material twisting the wall in the other direction would leave us looking at the wrong direction and make it invisible.

Load the page now and you should notice that the tiny bit of black you used to be able to see to the empty left of our wall has disappeared. That’s because there is now a left wall attached to it.

Now let’s add another wall to the right and one right behind the camera.

var wall3 = new THREE.Mesh( wallGeometry, wallMaterial)
 wall3.position.x = 0.5;
 wall3.rotation.y = -Math.PI/2;
 scene.add( wall3 );
 
 var wall4 = new THREE.Mesh( wallGeometry, wallMaterial)
 wall4.position.z = 0.5;
 wall4.rotation.y = Math.PI;
 scene.add( wall4 );

Now the white rectangle should go all the way from the left side of the screen to the right. But how do we make sure that the wall behind the camera was properly placed?

Easiest way is to add a little code to the render loop to make the camera spin so we can see all four walls of the room.

var render = function () {
   requestAnimationFrame( render );

   camera.rotation.y += 0.01;

   renderer.render(scene, camera);
};

Run the code now and you should look like you’re lazily spinning around in an office chair stuck in the middle of a room with pure white walls.

Although to be honest since the walls are pure white you might find that the whole thing looks more like one big white rectangle that keeps bulging and shrinking. There’s no strong sense of depth so it’s pretty easy to see the scene as a 2D animation instead of a 3D one.

Let’s fix this by adding some lighting. Lights and shadows will give the scene a strong sense of 3D.

But first we need to upgrade our material. The BasicMaterial we were using ignores lights and always looks the same no matter how bright or dark the scene is. So go find the line where we defined our material and change it to this:

var wallMaterial = new THREE.MeshStandardMaterial( );

This new wall material actually has a lighting system, which you can check this by reloading the code. Notice how the whole screen is suddenly pitch black? That’s because we don’t have any lights yet and standard materials can’t be seen without them.

So let’s give ourselves a light. Specifically we’ll be setting up a point light in the center of the room. A point light is basically a glowing point the shines equally in all directions, making it a great way to simulate light bulbs, torches and lanterns.

We can create a basic point light up by adding this code after our walls but before our rendering code:

var playerPointLight = new THREE.PointLight();
playerPointLight.position.set( 0, 0, 0 );
scene.add( playerPointLight );

Now run your code again. The point lighting should make the distant corners of the room much darker than the nearby centers of each wall, helping to improve the illusion that viewer is looking at a 3D space.

Monochromatic games are artsy and profound, right?

Cool! Technically we now know enough to build an entire maze. But let’s be honest, manually creating and positioning dozens or hundreds of walls sounds uper boring. So next time we’ll be building some utility code that will simplify maze building.