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I'm doing P2 physics collisions with: sprite.body.collides(collisionGroups, callback, this); and I'm trying to get some info on the momentum transfer of the collision to calculate damage, but I can't find the right values. What I've tried is to use the velocity difference like this: var impactSquare = Math.pow(p2BodyA.velocity.x - p2BodyB.velocity.x, 2) + Math.pow(p2BodyA.velocity.y - p2BodyB.velocity.y, 2); This works ok, but obviously it gives totally wrong values when the bodies fly towards each other and just barely touch, then deltaV is pretty high but there is basically no momentum transfer. Since there is no V_old and V_new (as far as I know) to get the change of velocity per sprite (pre and post collision) I've tried to look into using the deltaX values: dx = sprite.previousPosition.x - sprite.position.x ... but stopped there because it feels like an over-complicated and unreliable way to get something that should be somewhere in the data anyway Has anybody an idea where to look? Another (likely over-complicated) idea was to use the onBeginContact method to get the pre-collision velocity and store that somewhere so we can call it in the collides feedback, but ... well feels like there must be something simpler ...

Does anyone know how to rotate a sprite from it's current rotation? I'm having a Math brain fart. Here is my Sandbox example of the issue: http://phaser.io/sandbox/HhWNhhmR/play The sprite rotates around it's center when you drag it, but it always snaps to the mouse. How can we rotate it from where it currently is? I would love to have it respond in a similar way that PropellerJS works. As a bonus, it would be awesome to add the inertia and stepped angle constraints. Thanks!