File: src/collision/Pair.js
/**
* The `Matter.Pair` module contains methods for creating and manipulating collision pairs.
*
* @class Pair
*/
var Pair = {};
module.exports = Pair;
var Contact = require('./Contact');
(function() {
/**
* Creates a pair.
* @method create
* @param {collision} collision
* @param {number} timestamp
* @return {pair} A new pair
*/
Pair.create = function(collision, timestamp) {
var bodyA = collision.bodyA,
bodyB = collision.bodyB;
var pair = {
id: Pair.id(bodyA, bodyB),
bodyA: bodyA,
bodyB: bodyB,
collision: collision,
contacts: [],
activeContacts: [],
separation: 0,
isActive: true,
confirmedActive: true,
isSensor: bodyA.isSensor || bodyB.isSensor,
timeCreated: timestamp,
timeUpdated: timestamp,
inverseMass: 0,
friction: 0,
frictionStatic: 0,
restitution: 0,
slop: 0
};
Pair.update(pair, collision, timestamp);
return pair;
};
/**
* Updates a pair given a collision.
* @method update
* @param {pair} pair
* @param {collision} collision
* @param {number} timestamp
*/
Pair.update = function(pair, collision, timestamp) {
var contacts = pair.contacts,
supports = collision.supports,
activeContacts = pair.activeContacts,
parentA = collision.parentA,
parentB = collision.parentB,
parentAVerticesLength = parentA.vertices.length;
pair.isActive = true;
pair.timeUpdated = timestamp;
pair.collision = collision;
pair.separation = collision.depth;
pair.inverseMass = parentA.inverseMass + parentB.inverseMass;
pair.friction = parentA.friction < parentB.friction ? parentA.friction : parentB.friction;
pair.frictionStatic = parentA.frictionStatic > parentB.frictionStatic ? parentA.frictionStatic : parentB.frictionStatic;
pair.restitution = parentA.restitution > parentB.restitution ? parentA.restitution : parentB.restitution;
pair.slop = parentA.slop > parentB.slop ? parentA.slop : parentB.slop;
collision.pair = pair;
activeContacts.length = 0;
for (var i = 0; i < supports.length; i++) {
var support = supports[i],
contactId = support.body === parentA ? support.index : parentAVerticesLength + support.index,
contact = contacts[contactId];
if (contact) {
activeContacts.push(contact);
} else {
activeContacts.push(contacts[contactId] = Contact.create(support));
}
}
};
/**
* Set a pair as active or inactive.
* @method setActive
* @param {pair} pair
* @param {bool} isActive
* @param {number} timestamp
*/
Pair.setActive = function(pair, isActive, timestamp) {
if (isActive) {
pair.isActive = true;
pair.timeUpdated = timestamp;
} else {
pair.isActive = false;
pair.activeContacts.length = 0;
}
};
/**
* Get the id for the given pair.
* @method id
* @param {body} bodyA
* @param {body} bodyB
* @return {string} Unique pairId
*/
Pair.id = function(bodyA, bodyB) {
if (bodyA.id < bodyB.id) {
return 'A' + bodyA.id + 'B' + bodyB.id;
} else {
return 'A' + bodyB.id + 'B' + bodyA.id;
}
};
})();