motion.cs

for (var i = 0; i < 12; ++i) {
    g = GameObject.Instantiate(prefab);
    g.transform.SetParent(prefab.transform.parent);
    g.transform.localPosition = Vector3.zero;
    g.transform.localScale = Vector3.one;

    var angle = 30f * i;
    var radius = Velocity.AccelByRatio(218f, Source.Constant(0.92f)).Offset(83f);
    var speed = Velocity.AccelByRatio(0.75f, Source.Constant(0.94f)).Offset(0.01f);
    g.MotionP().Circular(radius, speed).Angle(angle).Fbm(new Vector2(0f, 1f), 3).AmplifyComponents(new Vector2(0f, 0.3f));
}

解説はこちら

UrMotion でめっちゃ簡単にモーションを作る for Unity - Qiita
http://qiita.com/beinteractive/items/52a937e08fcb88ac06f2