planck-js/lib/shape/CollideCircle.js

2D physics engine for JavaScript/HTML5 game development

/*
 * Copyright (c) 2016      Ali Shakiba http://shakiba.me/planck.js
 * Copyright (c) 2006-2011 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.
 */

var create = require('../util/create');
var Settings = require('../Settings');
var Shape = require('../Shape');
var Contact = require('../Contact');
var Manifold = require('../Manifold');
var Math = require('../common/Math');
var Transform = require('../common/Transform');
var Vec2 = require('../common/Vec2');

var CircleShape = require('./CircleShape');

Contact.AddType(CircleShape.TYPE, CircleShape.TYPE, CircleCircleContact);

function CircleCircleContact(manifold, xfA, fixtureA, indexA, xfB, fixtureB,
    indexB) {
  Assert(fixtureA.GetType() == CircleShape.TYPE);
  Assert(fixtureB.GetType() == CircleShape.TYPE);
  CollideCircles(manifold, fixtureA.GetShape(), xfA, fixtureB.GetShape(), xfB);
}

function CollideCircles(manifold, circleA, xfA, circleB, xfB) {
  manifold.pointCount = 0;

  var pA = Transform.Mul(xfA, circleA.m_p);
  var pB = Transform.Mul(xfB, circleB.m_p);

  var distSqr = Vec2.DistanceSquared(pB, pA);
  var rA = circleA.m_radius;
  var rB = circleB.m_radius;
  var radius = rA + rB;
  if (distSqr > radius * radius) {
    return;
  }

  manifold.type = Manifold.e_circles;
  manifold.localPoint.Set(circleA.m_p);
  manifold.localNormal.SetZero();
  manifold.pointCount = 1;
  manifold.points[0].localPoint.Set(circleB.m_p);
  manifold.points[0].id.key = 0;
}