function filter(p) {    
	
	/* Clamp velocity to maxVelocity units/second. Zeroing each component of acceleration keeps us from slamming.*/
	var maxVelocity = 5;
    function sign(val) {
        if (val > 0) {
            return 1;
        } else if (val < 0) {
            return -1;
        } else {
            return 0;
        }
    }
    if (p.velocity) {
        /* Random near-zero value used as "zero" to prevent two sequential updates from being
        exactly the same (which would cause them to be ignored) */
        var nearZero = 0.0001 * Math.random() + 0.001;
		if (Math.abs(p.velocity.x) > maxVelocity) {
			p.velocity.x = sign(p.velocity.x) * (maxVelocity + nearZero);
			p.acceleration.x = nearZero;
		}
		if (Math.abs(p.velocity.y) > maxVelocity) {
			p.velocity.y = sign(p.velocity.y) * (maxVelocity + nearZero);
			p.acceleration.y = nearZero;
		}
		if (Math.abs(p.velocity.z) > maxVelocity) {
			p.velocity.z = sign(p.velocity.z) * (maxVelocity + nearZero);
			p.acceleration.z = nearZero;
		}
    }

    return p;
}