public Fish()
{
this.model = Resources.fish_model;
this.size = Vector3.One;
this.speed = 2;
this.max_speed = (float)rand.NextDouble()*2 + 0.5f;
this.time = new TimeSpan();
skinning_data = model.Tag as SkinningData;
if (skinning_data == null)
throw new InvalidOperationException
("This model does not contain a SkinningData tag.");
animation_player = new AnimationPlayer(skinning_data);
StartDefaultClip();
Update(0);
}