planck-js/example/ApplyForce.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.
 */

planck.testbed('Apply Force', function(testbed) {
  testbed.y = -20;

  var pl = planck, Vec2 = pl.Vec2;

  var world = pl.World();

  var ground = world.createBody(Vec2(0.0, 20.0));

  var wallFD = {
    density: 0.0,
    restitution: 0.4,
  };

  // Left vertical
  ground.createFixture(pl.Edge(Vec2(-20.0, -20.0), Vec2(-20.0, 20.0)), wallFD);

  // Right vertical
  ground.createFixture(pl.Edge(Vec2(20.0, -20.0), Vec2(20.0, 20.0)), wallFD);

  // Top horizontal
  ground.createFixture(pl.Edge(Vec2(-20.0, 20.0), Vec2(20.0, 20.0)), wallFD);

  // Bottom horizontal
  ground.createFixture(pl.Edge(Vec2(-20.0, -20.0), Vec2(20.0, -20.0)), wallFD);

  var xf1 = pl.Transform();
  xf1.q.set(0.3524 * Math.PI);
  xf1.p.set(xf1.q.getXAxis());

  var poly1 = pl.Polygon([Vec2(-1.0, 0.0), Vec2(1.0, 0.0), Vec2(0.0, 0.5)].map(pl.Transform.mulFn(xf1)));

  var xf2 = pl.Transform();
  xf2.q.set(-0.3524 * Math.PI);
  xf2.p.set(Vec2.neg(xf2.q.getXAxis()));

  var poly2 = pl.Polygon([Vec2(-1.0, 0.0), Vec2(1.0, 0.0), Vec2(0.0, 0.5)].map(pl.Transform.mulFn(xf2)));

  var jet = world.createBody({
    type : 'dynamic',
    angularDamping : 2.0,
    linearDamping : 0.5,
    position : Vec2(0.0, 2.0),
    angle : Math.PI,
    allowSleep : false
  });

  jet.createFixture(poly1, 2.0);
  jet.createFixture(poly2, 2.0);

  var boxFD = {
    density: 1.0,
    friction: 0.3,
  };

  for (var i = 0; i < 10; ++i) {
    var box = world.createDynamicBody(Vec2(0.0, 5.0 + 1.54 * i));

    box.createFixture(pl.Box(0.5, 0.5), boxFD);

    var gravity = 10.0;
    var I = box.getInertia();
    var mass = box.getMass();

    // For a circle: I = 0.5 * m * r * r ==> r = sqrt(2 * I / m)
    var radius = Math.sqrt(2.0 * I / mass);

    world.createJoint(pl.FrictionJoint({
      collideConnected : true,
      maxForce : mass * gravity,
      maxTorque : mass * radius * gravity
    }, ground, box));
  }

  testbed.step = function() {
    if (testbed.activeKeys.right && !testbed.activeKeys.left) {
      jet.applyAngularImpulse(-0.2, true);

    } else if (testbed.activeKeys.left && !testbed.activeKeys.right) {
      jet.applyAngularImpulse(+0.2, true);
    }

    if (testbed.activeKeys.up) {
      var f = jet.getWorldVector(Vec2(0.0, -1.0));
      var p = jet.getWorldPoint(Vec2(0.0, 2.0));
      jet.applyLinearImpulse(f, p, true);
    }
  };

  return world;
});