This week I showed you a HTML5 prototype of “Fling” game built with Phaser and Matter.js but it was flawed by varios Matter.js issues.
Actually we can’t talk about “issues” because it was me trying to force the way Matter.js handles the constraints, but in the end I wasn’t satisfied.
So I studied a bit how constraints work and wrote about three ways to deal with constraints.
Finally I sorted out things and now I got something enjoyable:
Click the mouse to fire the hook towards mouse pointer, click again when swinging to release it, then click again to fire another hook and pretend to be Spider-Man.
This is the updated source code:
let game; let gameOptions = { gravity: 1, // game gravity terrainObjects: 20, // amount of terrain objects heroSize: 20, // hero size constraintSpeed: 2, // constraint shrinkage speed minBoxSize: 50, // minimum box size maxBoxSize: 200, // maximum box size hookSpeed: 20, // speed use to fire the hook ropeTolerance: 6 // rope tolerance. Used to avoid body trespassing } const WALL = 0; const BALL = 1; const HOOK = 2; window.onload = function() { // game configuration let gameConfig = { type: Phaser.AUTO, scale: { mode: Phaser.Scale.FIT, autoCenter: Phaser.Scale.CENTER_BOTH, parent: "thegame", width: 1334, height: 750 }, scene: playGame, physics: { default: "matter", matter: { gravity: { y: gameOptions.gravity }, debug: true } } } game = new Phaser.Game(gameConfig); window.focus(); } class playGame extends Phaser.Scene{ constructor(){ super("PlayGame"); } create(){ // I want physics world to be updated 30 times per second this.matter.world.update30Hz(); // adding world bounds. Basically four walls this.matter.world.setBounds(10, 10, game.config.width - 20, game.config.height - 20); // placing some random static boxes labeled as WALL for (let i = 0; i < gameOptions.terrainObjects; i++){ let posX = Phaser.Math.Between(0, game.config.width); let posY = Phaser.Math.Between(0, game.config.height); let width = Phaser.Math.Between(gameOptions.minBoxSize, gameOptions.maxBoxSize); let height = Phaser.Math.Between(gameOptions.minBoxSize, gameOptions.maxBoxSize); let poly = this.matter.add.rectangle(posX, posY, width, height, { isStatic: true }); poly.label = WALL; } // adding a bouncing ball labeled as BALL this.hero = this.matter.add.rectangle(game.config.width / 2, game.config.height / 2, gameOptions.heroSize, gameOptions.heroSize, { restitution: 0.5 }); this.hero.label = BALL; // the hook this.hook = null; // event listeners this.input.on("pointerdown", this.fireHook, this); // no ropes at the beginning this.rope = null; // collision listener this.matter.world.on("collisionstart", function(e, b1, b2){ // when the hook collides with something, let's make it static and create the joint if((b1.label == HOOK || b2.label == HOOK) && !this.rope){ // make the hook static Phaser.Physics.Matter.Matter.Body.setStatic(this.hook, true); // calculate the distance between the ball and the hook let distance = Phaser.Math.Distance.Between(this.hero.position.x, this.hero.position.y, this.hook.position.x, this.hook.position.y); // is the distance fairly greater than hero size? if(distance > gameOptions.heroSize * 2){ // add the constraint this.rope = this.matter.add.constraint(this.hero, this.hook, distance, 0.1); } } }, this) } // method to fire the hook fireHook(e){ // do we have a constraint? if(this.hook){ // destroy current constraint this.releaseHook(); } // don't we have a constraint? else{ // calculate the angle between the pointer and the ball let angle = Phaser.Math.Angle.Between(this.hero.position.x, this.hero.position.y, e.position.x, e.position.y); this.hook = this.matter.add.rectangle(this.hero.position.x + (gameOptions.heroSize * 2) * Math.cos(angle), this.hero.position.y + (gameOptions.heroSize * 2) * Math.sin(angle), 10, 10); this.hook.label = HOOK; // give the hook the proper velocity Phaser.Physics.Matter.Matter.Body.setVelocity(this.hook, { x: gameOptions.hookSpeed * Math.cos(angle), y:gameOptions.hookSpeed * Math.sin(angle) }); } } // method to remove the hook releaseHook(){ // is there a constraint? Remove it if(this.rope){ this.matter.world.removeConstraint(this.rope); this.rope = null; } // is there a hook? Remove it if(this.hook){ this.matter.world.remove(this.hook); this.hook = null; } } // method to be executed at every frame update(){ // is there a constraint? Shrink it if(this.rope){ this.rope.length -= gameOptions.constraintSpeed; let hookPosition = this.hook.position; let heroPosition = this.hero.position; let distance = Phaser.Math.Distance.Between(hookPosition.x, hookPosition.y, heroPosition.x, heroPosition.y); if(distance - this.rope.length > gameOptions.ropeTolerance){ this.rope.length = distance; } this.rope.length = Math.max(this.rope.length, gameOptions.heroSize * 2); } } };
Just like in the 3rd example in the post Understanding how Matter.js constraints work with Phaser if the actual distance between the player and the hook differs from the constraint length, we set constraint length to such distance. Download the source code.