Maintain speed after collision

[finspin]

I have 2 bouncing balls which are bouncing off world borders and also off each other. The balls do maintain their speed when bouncing off the world borders but they lose their speed when bouncing off each other.

 

I'd like them to maintain their speed after they collide with each other. I realise this is quite against the physics but is this doable?

 

Here it the game implemented with p2 physics http://finspin.github.io/bubble-game/version-2/ and the code below. And here is the same game implemented with arcade engine where balls are bouncing without losing the speed http://finspin.github.io/bubble-game/version-1/. I switched from the arcade engine to p2 after I learned arcade can't handle collision of circular objects.

var game = new Phaser.Game(480, 640, Phaser.AUTO, 'Bubble Game', {    preload: preload,    create: create,    update: update,    render: render});var b1, b2, bubble1, bubble2;function preload() {}function create() {    game.stage.backgroundColor = "#000";    game.physics.startSystem(Phaser.Physics.P2JS);    game.physics.p2.setImpactEvents(true);    var bubbleCollisionGroup = game.physics.p2.createCollisionGroup();    game.physics.p2.updateBoundsCollisionGroup();    b1 = game.add.graphics();    b1.beginFill(0xFF0000, 1);    b1.drawCircle(0, 0, 50);    bubble1 = game.add.sprite(game.world.width - 380, game.world.height - 50);    bubble1.addChild(b1);    bubble1.anchor.setTo(0.5, 0.5);    b2 = game.add.graphics();    b2.beginFill(0xFFFFFF, 1);    b2.drawCircle(0, 0, 50);    bubble2 = game.add.sprite(game.world.width - 245, game.world.height - 50);    bubble2.addChild(b2);    bubble2.anchor.setTo(0.5, 0.5);    bubbles = game.add.group();    bubbles.add(bubble1);    bubbles.add(bubble2);    game.physics.p2.enable(bubbles);    bubbles.forEach(function (bubble) {        bubble.body.setCircle(50);        bubble.body.setCollisionGroup(bubbleCollisionGroup);        bubble.body.collides([bubbleCollisionGroup, bubbleCollisionGroup]);    });    var bubbleMaterial = game.physics.p2.createMaterial('bubbleMaterial');    var worldMaterial = game.physics.p2.createMaterial('worldMaterial');    bubble1.body.setMaterial(bubbleMaterial);    bubble2.body.setMaterial(bubbleMaterial);    game.physics.p2.setWorldMaterial(worldMaterial, true, true, true, true);    var contactMaterial = game.physics.p2.createContactMaterial(bubbleMaterial, worldMaterial);    contactMaterial.friction = 0;    contactMaterial.restitution = 1.0;    bubble1.body.damping = 0;    bubble1.body.velocity.x = 200;    bubble1.body.velocity.y = -200;    bubble2.body.damping = 0;    bubble2.body.velocity.x = -100;    bubble2.body.velocity.y = 250;}function update() {}function render() {}

[Skeptron]

Could this post help? : http://www.html5gamedevs.com/topic/7474-set-constant-velocity-for-body-physicsp2js/

 

There seems to be a 'restitution' factor, maybe it's what you are looking for