Let’s Program A 3D Browser Game Part 3: Feeling Boxed In

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.

Let’s Program A 3D Browser Game Part 2: Three.js To The Rescue

Sorry For The Delay

My original plan was to show how to program a 3D web application from scratch, but after several rewrites I’ve come to the conclusion I can’t really do that without spending weeks worth of posts talking about general 3D programming. If that’s what you really want I suggest hitting this tutorial. Please note that none of their sample code will work unless you also download the helper libraries they provide in the online code repository. Just copy pasting their examples will fail without them.

As for me, I’m going to use a third party library to help us jump right into web based 3D without having to mess around too much with linear algebra and view frustums, which are all quite interesting but a bit too deep for the casual and fun game programming series I wanted to write here.

The particular library we’ll be using is called “three.js”, which can be downloaded at threejs.org. They also have plenty of documentation and examples there so if you find you enjoy the little application we’re writing here you’ll know where to go next to learn some more advanced tricks.

Let’s Get To Work

Go ahead and download three.js and grab the relatively small “three.min.js” file it comes with. Unless you’re planning on editing the library itself (and we aren’t) that’s all you really need so toss a copy of it into a new folder called something like “3dwebmaze” and create a blank “index.html” file right next to it. Now pop open your index in your favorite text editor and get ready for some coding.

First things first: we need to set up the basic webpage where all of our cool 3D stuff is going to happen. Our main requirements are to set up a canvas, make sure we load the three.js library and then tell the body of the webpage to trigger a script after it finishes loading. The script we want it to trigger will, of course, be the 3d maze program we’re going to write.

   <title>Maze With three.js</title>
   <script src="three.min.js"></script>
      function runMaze()
<body onload="runMaze();">
   <canvas id="mazeCanvas" width=600 height=450 />

With the boring stuff out of the way we can start writing some real code and filling in our runMaze function. Please note that every line of code in this particular post needs to go inside of runMaze.

The first thing runMaze needs to do is grab a reference to our canvas. Not only do we need to tell three.js where to find its drawing target, we also need to be able to grab the canvas’s width and height in order to fine tune various bits of our rendering process.

var mazeCanvas = document.getElementById("mazeCanvas");

After that we need to set up three js itself. First up is a “scene” whose job is to keep track of all the objects we want to draw. Just creating a 3D shape isn’t enough, you have to add it to the scene for anything to happen.

var scene = new THREE.Scene();

Next we need to set up the renderer, which does all the work of actually drawing things. By default the renderer will try to create a brand new canvas but if you already have one you can pass a reference to it. Notice that we’re passing WebGLRenderer an anonymous object with a “canvas” property. Just passing the canvas reference alone won’t work; this function, like a lot of three.js, expects an object full of setup details instead of direct arguments.

var renderer = new THREE.WebGLRenderer({ canvas: mazeCanvas });

The last thing we need is a camera, which helps the renderer figure out exactly how things should be drawn to the screen. The camera needs four pieces of information to work properly, so buckle yourself in for a wall o’ text.

The first camera argument is “field of view”, which is kind of a weird idea. Think of it like this: humans and cameras see the world through a cone shape. Up close you can only see things right in front of you (like a single tree) but the farther away things are the wider an area you can see all at once (like miles of distant forest). Well field of view is just a measurement of what kind of vision cone you want your camera to have. Will it be a big wide panoramic camera or will it be more focused? The “best” cone shape depends heavily on what kind of scene you want to draw. For now we’ll choose a cone with a 75 degree angle and then tweak it later if we think that’s too wide / not wide enough.

The second piece of camera information is aspect ratio, or the shape of the final picture. This needs to match whatever you canvas size is or else things will get stretched and squished just like when you accidentally try to watch an old movie on a widescreen TV. The easiest way to make sure it’s right is to just calculate the aspect ratio on the spot based on the same canvas reference we passed to the renderer. That way if we later decide to change the size of the canvas the code here will automatically update the next time we reload the page.

The last two pieces of information are the minimum and maximum distances you want objects to appear at, commonly called the near and far plane of the view frustum. Anything closer to you than the near limit gets ignored (useful for making sure you don’t draw things behind or overlapping with your camera). Anything beyond the far limit also gets ignored (useful for making sure you don’t waste processing power drawing objects so far away they would barely be a blip on the screen anyways). Once again the exact values for these depend on what kind of scene you’re programming so for now we’ll just use the default values from the three.js online tutorial and then change them later if that doesn’t work.

Put those four pieces of information all together and we get this:

var camera = new THREE.PerspectiveCamera( 75, mazeCanvas.width/mazeCanvas.height, 0.1, 1000 );

With that three.js is all set up and ready for us to start building mazes.

I think it’s safe to say that the most important part of a maze is the walls. You can get away with leaving off the ceiling and people usually don’t look too closely at the floor but without walls it’s not a maze at all. So let’s draw some walls.

In general the easiest way to draw a wall is to just make a 2D rectangle and stick it the way of the player, and after a little experimentation I found that a wall twice as wide as it is tall seems to look the best. But exactly how tall should it be?

If this was a real life maze we’d probably base the height of our maze walls off of the average height of the people we want to explore it. Example: Almost all humans (at the time of this writing) are less than seven feet tall so an eight foot high wall should be enough to prevent anybody from bumping their head.

But this isn’t a physical maze. It’s a 3D graphics maze and the imaginary cameraman running through the maze is exactly 0 units tall and has no head to bump. That means that exact size of our walls doesn’t actually matter. We could make our walls HUGE and still get them to fit on screen by just putting them far away. We could also make them super tiny but still have them feel taller than the player by just putting them close together and right in the front of the camera. What matters isn’t the size of the wall, but the ratio of its size and camera distance.

This is nice because it means we can set the scale of our maze to whatever is most convenient to work with and then adjust the camera until everything looks appropriately player sized.

Now it seems to me that the most convenient scale for a grid based maze is to let every grid square be one unit wide and one unit long. That way we can easily convert between maze locations (column 5, row 3) and 3D positions (x:5, z:3). And of course if the grid squares are one unit wide every wall will also be 1 unit wide and to get the proper 2-to-1 width to height ratio that means every wall will be 0.5 units tall.

So now that we know what size our walls are going to be let’s finish up this post by building one and drawing it to screen. It will be one unit wide, half a unit tall and we will put it half a unit away from the camera. Since the camera, by default, sits at (0,0,0) and faces in the negative Z direction that means we want to put the wall at (0,0,-0.5).

Digital Carpentry

To build this wall we need two things:

1) Some geometry describing the shape of the wall

2) A “material” describing how the wall should be colored and textured.

var wallGeometry = new THREE.PlaneGeometry( 1, 0.5 );
 var wallMaterial = new THREE.MeshBasicMaterial( );
 var wall = new THREE.Mesh( wallGeometry, wallMaterial );
 wall.position.z = -0.5;
 scene.add( wall );

For our geometry we used a simple plane, basically a flat rectangle with whatever width and height we want.

For our material we use the default MeshBasicMaterial. Without any special arguments this represents a simple flat coat of white digital paint. The only interesting thing about is that it’s a one sided texture; you can only see it from the front. Look at the wall from behind and it’s invisible. This is actually very useful (and efficient) because most of the time you only want to draw one side of a shape anyways. We will only ever look at our maze from the inside and a character like Mario should only ever be seen from the outside.

Now that we have our rectangle and our boring white material we can mix them together into a an actual useable 3D mesh. We then push its z position away from the camera by half a unit and add the final objection to our scene. Remember, only objects that are part of the scene get rendered!

But how do we make that rendering happen? Simple enough, we just have to set up a function with a few three.js hooks and then call it.

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

   renderer.render(scene, camera);


And with that we have a wall. A single, bland wall that frankly doesn’t look very 3D at all. We could have done the same thing with a single 2D draw rectangle call. But it’s a start.

Yes, it’s a boring screenshot but just think how easy it would be to compress!

Bonus Project!

Earlier I said that the exact size of our wall didn’t matter since we could make small walls look big by getting up close or big walls look small by backing away. Test this out by making the wall two or five or ten times bigger (or smaller) while also changing its z position to be two or five or ten times further away (or closer). You should notice that as long as the ratio of size to distance is constant you’ll get the exact seem fills-most-of-the-screen rectangle no matter what sizes you choose.

Let’s Illustrate Planetbase Part 5: The Key To Success Is Low Expectations

Thanks to our unreliable wind turbine the Fault Inc base was able to barely scrape through the night without any causalities. And that means we unlock our first milestone: Survival. Admittedly making it through the game’s first day isn’t all that impressive but I’ll take whatever positive reinforcement I can get.

People in suits shaking hands is what business is all about, right?

All things considered that’s a LOT of construction work for one day, seven people a couple robots.

If you look at the full size screenshot you’ll notice a few potentially interesting things. Besides the turbine and the solar panels there’s a glowing blue cylinder. That’s a huge battery and while it wasn’t finished in time to help with the first night it should smooth out life support in the coming weeks. On the right side of the base there are a bunch of more of domes. Admittedly they are more or less identical so you’ll just have to take my word that one is a dorm, one is a cafeteria and one is a hydroponics space farm. That weird black skeleton is the beginnings of a mine so we can start properly exploiting this big ball of rock.

I’ll admit I wonder if I’m building too many different things too fast. Or too slowly. Guess we’ll have to find out the hard way.