planck-js/example/CollisionProcessing.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 test shows collision processing and tests
// deferred body destruction.
planck.testbed('CollisionProcessing', function(testbed) {
  var pl = planck, Vec2 = pl.Vec2;
  var world = pl.World(Vec2(0, -10));

  // Ground body
  world.createBody().createFixture(pl.Edge(Vec2(-50.0, 0.0), Vec2(50.0, 0.0)));

  var xLo = -5.0, xHi = 5.0;
  var yLo = 2.0, yHi = 35.0;

  // Small triangle
  var body1 = world.createDynamicBody(Vec2(pl.Math.random(xLo, xHi), pl.Math.random(yLo, yHi)));
  body1.createFixture(pl.Polygon([Vec2(-1.0, 0.0), Vec2(1.0, 0.0), Vec2(0.0, 2.0)]), 1.0);

  // Large triangle (recycle definitions)
  var body2 = world.createDynamicBody(Vec2(pl.Math.random(xLo, xHi), pl.Math.random(yLo, yHi)));
  body2.createFixture(pl.Polygon([Vec2(-1.0, 0.0), Vec2(1.0, 0.0), Vec2(0.0, 2.0)]), 1.0);

  // Small box
  var body3 = world.createDynamicBody(Vec2(pl.Math.random(xLo, xHi), pl.Math.random(yLo, yHi)));
  body3.createFixture(pl.Box(1.0, 0.5), 1.0);

  // Large box (recycle definitions)
  var body4 = world.createDynamicBody(Vec2(pl.Math.random(xLo, xHi), pl.Math.random(yLo, yHi)));
  body4.createFixture(pl.Box(2.0, 1.0), 1.0);

  // Small circle
  var body5 = world.createDynamicBody(Vec2(pl.Math.random(xLo, xHi), pl.Math.random(yLo, yHi)));
  body5.createFixture(pl.Circle(1.0), 1.0);

  // Large circle
  var body6 = world.createDynamicBody(Vec2(pl.Math.random(xLo, xHi), pl.Math.random(yLo, yHi)));
  body6.createFixture(pl.Circle(2.0), 1.0);

  var points = [];

  world.on('pre-solve', function(contact, oldManifold) {
    var manifold = contact.getManifold();

    if (manifold.pointCount == 0) {
      return;
    }

    var fixtureA = contact.getFixtureA();
    var fixtureB = contact.getFixtureB();

    var worldManifold = contact.getWorldManifold();

    for (var i = 0; i < manifold.pointCount; ++i) {
      var cp = {};
      cp.fixtureA = fixtureA;
      cp.fixtureB = fixtureB;
      cp.position = worldManifold.points[i];
      cp.normal = worldManifold.normal;
      // cp.state = state2[i];
      cp.normalImpulse = manifold.points[i].normalImpulse;
      cp.tangentImpulse = manifold.points[i].tangentImpulse;
      cp.separation = worldManifold.separations[i];
      points.push(cp);
    }
  });

  var bomb = null;
  var MAX_NUKE = 6;

  testbed.step = function() {

    // We are going to destroy some bodies according to contact
    // points. We must buffer the bodies that should be destroyed
    // because they may belong to multiple contact points.
    var nuke = [];

    // Traverse the contact results. Destroy bodies that
    // are touching heavier bodies.
    for (var i = 0; i < points.length && nuke.length < MAX_NUKE; ++i) {
      var point = points[i];

      var body1 = point.fixtureA.getBody();
      var body2 = point.fixtureB.getBody();
      var mass1 = body1.getMass();
      var mass2 = body2.getMass();

      if (mass1 > 0.0 && mass2 > 0.0) {
        if (mass2 > mass1) {
          nuke.push(body1);
        } else {
          nuke.push(body2);
        }
      }
    }

    for (var i = 0; i < nuke.length; i++) {
      var b = nuke[i];
      if (b != bomb) {
        world.destroyBody(b);
      }
    }

    points.length = 0;
  };

  return world;
});