planck-js/HelloWorld.js

2D JavaScript physics engine for cross-platform HTML5 game development

/*
 * MIT License
 * Copyright (c) 2019 Erin Catto
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

/*
 * This is a simple example of building and running a simulation
 * using Planck.js. Here we create a large ground box and a small dynamic
 * box.
 * There are no graphics for this example. Planck.js is meant to be used
 * with your rendering engine in your game engine.
 *
 * To run this example simply run `node HelloWorld.js` from command line.
 */

var planck = require('./lib')

var Vec2 = planck.Vec2;

// Define the gravity vector.
var gravity = Vec2(0.0, -10.0);

// Construct a world object, which will hold and simulate the rigid bodies.
var world = planck.World(gravity);

// Define the ground body.
var groundBodyDef = {
  position: Vec2(0.0, -10.0)
};

// Call the body factory which allocates memory for the ground body
// from a pool and creates the ground box shape (also from a pool).
// The body is also added to the world.
var groundBody = world.createBody(groundBodyDef);

// Define the ground box shape.
// The extents are the half-widths of the box.
var groundBox = planck.Box(50.0, 10.0);

// Add the ground fixture to the ground body.
groundBody.createFixture(groundBox, 0.0);

// Define the dynamic body. We set its position and call the body factory.
var bodyDef = {
    type: 'dynamic',
    position: Vec2(0.0, 4.0),
}
var body = world.createBody(bodyDef);

// Define another box shape for our dynamic body.
var dynamicBox = planck.Box(1.0, 1.0);

// Define the dynamic body fixture.
var fixtureDef = {
    shape: dynamicBox,
    // Set the box density to be non-zero, so it will be dynamic.
    density: 1.0,
    // Override the default friction.
    friction: 0.3,
};

// Add the shape to the body.
body.createFixture(fixtureDef);

// Prepare for simulation. Typically we use a time step of 1/60 of a
// second (60Hz) and 10 iterations. This provides a high quality simulation
// in most game scenarios.
var timeStep = 1.0 / 60.0;
var velocityIterations = 6;
var positionIterations = 2;


// This is our little game loop.
for (var i = 0; i < 60; ++i) {
    // Instruct the world to perform a single step of simulation.
    // It is generally best to keep the time step and iterations fixed.
    world.step(timeStep, velocityIterations, positionIterations);

    // Now print the position and angle of the body.
    var position = body.getPosition();
    var angle = body.getAngle();

    console.log(position.x.toFixed(2), position.y.toFixed(2), angle.toFixed(2));
}

console.log(Math.abs(position.x) < 0.01);
console.log(Math.abs(position.y - 1.01) < 0.01);
console.log(Math.abs(angle) < 0.01);