CollisionProcessing.js

/*
 * Copyright (c) 2016-2018 Ali Shakiba http://shakiba.me/planck.js
 * Copyright (c) 2006-2009 Erin Catto  http://www.box2d.org
 *
 * This software is provided 'as-is', without any express or implied
 * warranty.  In no event will the authors be held liable for any damages
 * arising from the use of this software.
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 * 1. The origin of this software must not be misrepresented; you must not
 * claim that you wrote the original software. If you use this software
 * in a product, an acknowledgment in the product documentation would be
 * appreciated but is not required.
 * 2. Altered source versions must be plainly marked as such, and must not be
 * misrepresented as being the original software.
 * 3. This notice may not be removed or altered from any source distribution.
 */

// 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 m_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];
      m_points.push(cp);
    }
  });

  var m_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 < m_points.length && nuke.length < MAX_NUKE; ++i) {
      var point = m_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 != m_bomb) {
        world.destroyBody(b);
      }
    }

    m_points.length = 0;
  };

  return world;
});