• Creating a 3D Game With Three.js and WebGL

    Comments Off on Creating a 3D Game With Three.js and WebGL
    April 18, 2020 /  Computer Technology, Programming

    Prerequisites

    • A browser with WebGL – this game has been tested on Chrome and Firefox. IE still doesn’t support WebGL, unless you’re using Windows 8.1 with IE11.
    • Three.js library available for download from the Three.js website
    • The Keyboard.js helper library I used for this project, created by Arthur Schreiber at No Karma. Download it from my GitHub repository
    • A basic understanding of what Three.js does. Read this super simple, super quick tutorial by Paul Lewis. It’s basically a short-hand version of this article.

    Setup

    Get a base index.html running

    Step one when making a web-based game is to create the host index.html file. In our case, it only needs to be a very simple set of elements, so we can bundle the CSS styling too.

    Import Keyboard.js and Three.js

    Three.js is a library contained in just one JavaScript file, so we can grab the minified version from the website.

    For Keyboard input, we will need to referencethe aforementioned JavaScript file in our index.html as well.

    Create setup() and draw() functions

    The setup() function will be the start point for the game code. The draw() function will be run every frame and will handle all the rendering and game logic.

    In order to loop the draw() function, we simply utilise the requestAnimationFrame() function call, and pass ‘draw’ as the parameter. Remember, not all browsers natively support the call, and you might have to use Paul Irish’s shim to gain maximum compatibility. Also, it is important to realise that requestAnimationFrame() does not guarantee a fixed frame-rate, so you need to use time-deltas to calculate realistic physics. For a basic game like Pong, we don’t really care about that.

    Basic World

    Set up the Three.js world and camera

    Three.js includes these important elements:

    • Scene
    • Renderer
    • Camera
    • Mesh
    • Light
    • Material

    Cameras, Meshes, and Lights need to be added to the scene using the scene.add() function.

    Attach a WebGL Three.js Renderer to the DIV

    The renderer is attached to whichever HTML DOM element you wish to render the scene to, and a render() call is made each frame to the renderer in order to draw the Three.js scene.

    Add a camera to the scene

    Three.js has the option to create Perspective and Orthographic cameras. For most uses, Perspective camera is the best choice. We can change position and rotation information of the camera like any other object in the scene.

    Draw a sphere and light it

    Meshes must be paired with Materials in order to give them a defined look and feel. Meshes can be of many types, include primitives such as Cube, Sphere, Plane and Torus. Materials can have different characteristics depending on their type. The basic Material types include Lambert, Phong, and Basic.

    • Basic renders an unlit Mesh with no shadows or dark shading. A sphere will look like a circle if rendered with Basic.
    • Lambert is a simple diffuse-like lighting that creates shading on sides facing away from a light source. It gives a basic 3D look of surfaces that are matte (non-shiny and non-reflective)
    • Phong is used for achieving a plastic-like look and feel, with the ability to gain highlights that give a much shinier appearance to the Mesh.

    Show off your sphere with a Point Light. This is the most basic light, with no direction or rotation. Make sure you tweak the light’s intensity and distance to get it looking good.

    Add Game Objects

    Draw playing area plane

    The playing area will be a Three.js Mesh object of type Plane. Make sure the plane matches the play area, giving a small buffer gap to indicate where the paddles can and can’t go.

    Draw paddles

    The paddles will be Mesh objects of type Cube. Position each of the paddles on opposite sides of the play area.

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    // set up the paddle vars
    paddleWidth = 10;
    paddleHeight = 30;
    paddleDepth = 10;
    paddleQuality = 1;
    // set up paddle 1
    paddle1 = new THREE.Mesh(
    new THREE.CubeGeometry(
    paddleWidth,
    paddleHeight,
    paddleDepth,
    paddleQuality,
    paddleQuality,
    paddleQuality),
    paddle1Material);
    // add the paddle to the scene
    scene.add(paddle1);
    // Set up the second paddle
    paddle2 = new THREE.Mesh(
    new THREE.CubeGeometry(
    paddleWidth,
    paddleHeight,
    paddleDepth,
    paddleQuality,
    paddleQuality,
    paddleQuality),
    paddle2Material);
    // Add the second paddle to the scene
    scene.add(paddle2);
    // set paddles on each side of the table
    paddle1.position.x = -fieldWidth/2 + paddleWidth;
    paddle2.position.x = fieldWidth/2 – paddleWidth;
    // lift paddles over playing surface
    paddle1.position.z = paddleDepth;
    paddle2.position.z = paddleDepth;
    view rawBNG_Pong_paddlecreateThis Gist brought to you by GitHub.

    If you manipulate the camera positions, as seen in the screenshot, you can give a different perspective to the player.

    Basic Logic

    Ball movement

    The ball will have an X-direction and a Y-direction that determines the movement per frame.

    // ball’s x-direction, y-direction and speed per frame
    var ballDirX = 1, ballDirY = 1, ballSpeed = 2;

    The ball will move at a constant speed in the X-plane every frame. To this end, we will specify a ballSpeed variable that acts as a multiplier for the direction values.

    // update ball position over time
    ball.position.x += ballDirX * ballSpeed;
    ball.position.y += ballDirY * ballSpeed;

    We want the ball to have some unpredictable characteristics (e.g. when it gets sliced quite hard) so we will allow the Y-direction to go up to a maximum of ballSpeed * 2. You can tweak the values until you’re happy with how the ball behaves.

    // limit ball’s y-speed to 2x the x-speed
    // this is so the ball doesn’t speed from left to right super fast
    // keeps game playable for humans
    if (ballDirY > ballSpeed * 2)
    {
    ballDirY = ballSpeed * 2;
    }
    else if (ballDirY < -ballSpeed * 2)
    {
    ballDirY = -ballSpeed * 2;
    }

    Ball wall bounce logic

    Simple collision detection logic is required to check if the ball is touching each of the side ‘walls’. Using a series of ‘if-else’ statements, we check the ball positions against the predetermined wall positions. In the case of a collision, we simply switch the Y-direction of the ball, creating a bounce effect.

    // if ball goes off the top side (side of table)
    if (ball.position.y <= -fieldHeight/2)
    {
    ballDirY = -ballDirY;
    }
    // if ball goes off the bottom side (side of table)
    if (ball.position.y >= fieldHeight/2)
    {
    ballDirY = -ballDirY;
    }

    Later, we will edit some of this code in order to implement scoring when the ball passes a paddle.

    Keyboard input for paddles

    We will utilise a very effective short-cut in order to easily get keyboard input working in this game. Using the Keyboard.js file provided, we simply have to include the reference to it in the index.html file and we are set. Only one function call is required, the Key.isDown() call. Given a parameter, the library checks if that particular key is current being pressed, and returns a boolean value.

    // move left
    if (Key.isDown(Key.A))
    {
    // code to move paddle left
    }

    We use the ‘A’ and ‘D’ keys to move the paddle left and right, but you can edit the Keyboard.js with additional values if you want to use your own control scheme.

    var Key = {
    _pressed: {},
    A: 65,
    W: 87,
    D: 68,
    S: 83,
    // add your required key code (ASCII) along with the name here
    // for example:
    SPACE: 32,
    };

    While dealing with keyboard input, it is also important to ensure that the input is never blindly updated in game. We have to check that the paddle isn’t made to move off the play area, and we do that with some ‘if-else’ statements as well.

    // move left
    if (Key.isDown(Key.A))
    {
    // if paddle is not touching the side of table
    // we move
    if (paddle1.position.y < fieldHeight * 0.45)
    {
    paddle1DirY = paddleSpeed * 0.5;
    }
    // else we don’t move and stretch the paddle
    // to indicate we can’t move
    else
    {
    paddle1DirY = 0;
    paddle1.scale.z += (10 – paddle1.scale.z) * 0.2;
    }
    }

    Note that we use a paddle direction variable, rather than simply applying a change to the position values. This will come in handy when programming the ball to ‘slice’ when hit at an angle with a fast-moving paddle.

    Opponent logic

    When you code a game of this calibre, it is of utmost importance that you create a vivid, lush environment with a host of emotional, highly-relatable characters that showcase this generation’s strides forward in technology. Instead, we will code a Pong A.I. that blindly follows the ball, because that is even better.

    We can update the opponent difficulty by using a variable instead of introducing magic numbers. This variable will affect the ‘reaction rate’ of the opponent by increasing the Lerp (Linear-Interpolation) time.

    When using a Lerp (Linear-Interpolation) function, we must ensure the opponent plays fairly by limiting their maximum travel speed. We do that with a few more if-else statements.

    // in case the Lerp function produces a value above max paddle speed, we clamp it
    if (Math.abs(paddle2DirY) <= paddleSpeed)
    {
    paddle2.position.y += paddle2DirY;
    }
    // if the lerp value is too high, we have to limit speed to paddleSpeed
    else
    {
    // if paddle is lerping in +ve direction
    if (paddle2DirY > paddleSpeed)
    {
    paddle2.position.y += paddleSpeed;
    }
    // if paddle is lerping in -ve direction
    else if (paddle2DirY < -paddleSpeed)
    {
    paddle2.position.y -= paddleSpeed;
    }
    }
    If want to extend immersion, you could also using the paddle.scale property to stretch the paddle when it can’t be moved. This indicates an issue to the player which they can then address immediately. In order to accomplish this, we must ensure the paddle always Lerps back to the default scale size.
    // We lerp the scale back to 1
    // this is done because we stretch the paddle at some points
    // stretching is done when paddle touches side of table and when paddle hits ball
    // by doing this here, we ensure paddle always comes back to default size
    paddle2.scale.y += (1 – paddle2.scale.y) * 0.2;

    Adding Gameplay

    Making the ball reset after missing a paddle

    To get the main scoring gameplay working, we need to first remove the ball’s ability to bonce off the paddle-facing walls. To do this, we remove the bounce code from the two corresponding if-else statements.

    // if ball goes off the top side (side of table)
    if (ball.position.y <= -fieldHeight/2)
    {
    ballDirY = -ballDirY;
    }
    // if ball goes off the bottom side (side of table)
    if (ball.position.y >= fieldHeight/2)
    {
    ballDirY = -ballDirY;
    }
    //// ——————————— ////
    CHANGED CODE
    //// ——————————— ////
    // if ball goes off the ‘left’ side (Player’s side)
    if (ball.position.x <= -fieldWidth/2)
    {
    // CPU scores a point
    // update scoreboard
    // and reset ball
    }
    // if ball goes off the ‘right’ side (CPU’s side)
    if (ball.position.x >= fieldWidth/2)
    {
    // player scores a point
    // update scoreboard
    // and reset ball
    }

    We can handle scoring in many different ways. For a simple game like this, we can simply increment the corresponding score count variable.

    // if ball goes off the ‘left’ side (Player’s side)
    if (ball.position.x <= -fieldWidth/2)
    {
    // CPU scores
    score2++;
    // update scoreboard HTML
    document.getElementById(“scores”).innerHTML = score1 + “-” + score2;
    // reset ball to center
    resetBall(2);
    // check if match over (someone scored maxScore points)
    matchScoreCheck();
    }

    We can then update the HUD element in the DOM by setting its innerHTML value. Finally, we have to reset the ball once someone has scored. A simple function can be written to reset the ball, with a parameter indicating which paddle just lost (so we know which paddle to send the ball to next time).

    // resets the ball’s position to the centre of the play area
    // also sets the ball direction speed towards the last point winner
    function resetBall(loser)
    {
    // position the ball in the center of the table
    ball.position.x = 0;
    ball.position.y = 0;
    // if player lost the last point, we send the ball to opponent
    if (loser == 1)
    {
    ballDirX = -1;
    }
    // else if opponent lost, we send ball to player
    else
    {
    ballDirX = 1;
    }
    // set the ball to move +ve in y plane (towards left from the camera)
    ballDirY = 1;
    }

    Making the ball bounce off paddles

    Alright, this is it. The big one. Literally the biggest feature of this game. It’s time to get the paddles hitting the ball. In a simple Pong game, paddle-ball physics are nothing more than a couple of if-else statements. We check the X-position and Y-position of the ball against the paddle’s rectangular bounds, and if they intersect, we bounce the ball away.

    // if ball is aligned with paddle1 on x plane
    // remember the position is the CENTER of the object
    // we only check between the front and the middle of the paddle (one-way collision)
    if (ball.position.x <= paddle1.position.x + paddleWidth
    && ball.position.x >= paddle1.position.x)
    {
    // and if ball is aligned with paddle1 on y plane
    if (ball.position.y <= paddle1.position.y + paddleHeight/2
    && ball.position.y >= paddle1.position.y – paddleHeight/2)
    {
    // ball is intersecting with the front half of the paddle
    }
    }

    It’s also important to check the direction of the ball’s travel, as we only want to check collisions in one direction (the direction towards the opponent.)

    // and if ball is travelling towards player (-ve direction)
    if (ballDirX < 0)
    {
    // stretch the paddle to indicate a hit
    paddle1.scale.y = 15;
    // switch direction of ball travel to create bounce
    ballDirX = -ballDirX;
    // we impact ball angle when hitting it
    // this is not realistic physics, just spices up the gameplay
    // allows you to ‘slice’ the ball to beat the opponent
    ballDirY -= paddle1DirY * 0.7;
    }

    We will also affect the ball’s lateral movement depending on the relative speed of the paddle when hitting the ball. This is particularly useful in introducing the biggest variable in Pong: the slice. Slicing the ball is often the only way to confuse and outmaneuver the opponent, so it is vital in this game.

    Remember to duplicate the code, but update the values to match the opponent’s paddle. You can use this opportunity to gimp your opponent’s ability somewhat, by reducing the hitbox size or decreasing the slice amount. It’s what we would all do.

    Here is the final paddle-ball collision function:

    // Handles paddle collision logic
    function paddlePhysics()
    {
    // PLAYER PADDLE LOGIC
    // if ball is aligned with paddle1 on x plane
    // remember the position is the CENTER of the object
    // we only check between the front and the middle of the paddle (one-way collision)
    if (ball.position.x <= paddle1.position.x + paddleWidth
    && ball.position.x >= paddle1.position.x)
    {
    // and if ball is aligned with paddle1 on y plane
    if (ball.position.y <= paddle1.position.y + paddleHeight/2
    && ball.position.y >= paddle1.position.y – paddleHeight/2)
    {
    // and if ball is travelling towards player (-ve direction)
    if (ballDirX < 0)
    {
    // stretch the paddle to indicate a hit
    paddle1.scale.y = 15;
    // switch direction of ball travel to create bounce
    ballDirX = -ballDirX;
    // we impact ball angle when hitting it
    // this is not realistic physics, just spices up the gameplay
    // allows you to ‘slice’ the ball to beat the opponent
    ballDirY -= paddle1DirY * 0.7;
    }
    }
    }
    // OPPONENT PADDLE LOGIC
    // if ball is aligned with paddle2 on x plane
    // remember the position is the CENTER of the object
    // we only check between the front and the middle of the paddle (one-way collision)
    if (ball.position.x <= paddle2.position.x + paddleWidth
    && ball.position.x >= paddle2.position.x)
    {
    // and if ball is aligned with paddle2 on y plane
    if (ball.position.y <= paddle2.position.y + paddleHeight/2
    && ball.position.y >= paddle2.position.y – paddleHeight/2)
    {
    // and if ball is travelling towards opponent (+ve direction)
    if (ballDirX > 0)
    {
    // stretch the paddle to indicate a hit
    paddle2.scale.y = 15;
    // switch direction of ball travel to create bounce
    ballDirX = -ballDirX;
    // we impact ball angle when hitting it
    // this is not realistic physics, just spices up the gameplay
    // allows you to ‘slice’ the ball to beat the opponent
    ballDirY -= paddle2DirY * 0.7;
    }
    }
    }
    }
    view rawBNG_Pong_paddlecollCompleteThis Gist brought to you by GitHub.

    Scoring

    In Pong, it is usually simplest to have a maximum score value, such that a game is won when either player reaches that score. To that end, we can easily create a maxScore variable and set it at the start of the match.

    We then create a function to check if either player has scored equal or higher than the maximum. This function should be called only when a score has been changed (i.e. when someone scores a point.)

    // checks if either player or opponent has reached 7 points
    function matchScoreCheck()
    {
    // if player has 7 points
    if (score1 >= maxScore)
    {
    // stop the ball
    ballSpeed = 0;
    // write to the banner
    document.getElementById(“scores”).innerHTML = “Player wins!”;
    document.getElementById(“winnerBoard”).innerHTML = “Refresh to play again”;
    }
    // else if opponent has 7 points
    else if (score2 >= maxScore)
    {
    // stop the ball
    ballSpeed = 0;
    // write to the banner
    document.getElementById(“scores”).innerHTML = “CPU wins!”;
    document.getElementById(“winnerBoard”).innerHTML = “Refresh to play again”;
    }
    }

    After a match is deemed complete, it is simplest to just return the ball to the centre and stop any movement, so that play doesnt inadvertently continue.

    Prettifying the Game

    HUD

    It’s important to give feedback to the player so they know what’s going on. For Pong, the least we can do is keep a scoreboard ticking over. Instead of trying to draw the HUD on the same layer as the game, we can use the other DOM elements to provide the required feedback.

    It’s also good to indicate the maximum score as well, so we have another element for that which we will update at match start.

    // update the board to reflect the max score for match win
    document.getElementById(“winnerBoard”).innerHTML = “First to ” + maxScore + ” wins!”;

    Shadows

    Finally, it is time to make things look a tad more polished. Three.js has the awesome ability to create shadows for primitive objects (Cube, Plane, Sphere, etc.) so we can utilise that to make the game look nicer.

    Shadows can’t be created with just a Point light, so we have to add a DirectionalLight or a SpotLight. A SpotLight shines a circular beam of light onto surfaces, which DirectionalLight simply shines a light in a certain direction with no regard to positioning.

    We will use a SpotLight because it clearly indicates where the light originates from and shines towards.

    We can update the SpotLight to follow the ball around to give a more dynamic look and feel to the game, whilst showcasing the hard work we just put into the lighting.

    // we can easily notice shadows if we dynamically move lights during the game
    spotLight.position.x = ball.position.x;
    spotLight.position.y = ball.position.y;

    To make an object in the scene cast or receive shadows, we simply set their .receiveShadow and .castShadow variables to true. For example,

    paddle1 = new THREE.Mesh(
    new THREE.CubeGeometry(paddleWidth, paddleHeight, paddleDepth, paddleQuality, paddleQuality, paddleQuality),
    paddle1Material);
    // add the sphere to the scene
    scene.add(paddle1);
    paddle1.receiveShadow = true;
    paddle1.castShadow = true;

    Conclusion

    This is but a basic introduction to the power of Three.js, which should allow you to create a basic Pong clone.

    Play the latest build of this game here: LATEST BUILD*

    Find the latest code at its GitHub page*

    You can still do quite a number of things to polish your game, such as

    • Create animations for the paddles and ball
    • Update the HUD to look prettier
    • Import complex objects created in Modeling packages, to design a more immersive environment
    • Move HUD elements inside the game view to allow for full-screen gaming
    • Mess around with complex shaders to create reflections and other cool effects

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