Integrator = function(_value, _damping, _attraction)
{
	var _self = this;
	var DAMPING = 0.5;
	var ATTRACTION = 0.2;
	
	var vel = 0;//速度
	var accel = 0;//加速度
	var force = 0;//力
	var mass = 1;//質量
	var damping;//制動係数
	var attraction;//引力
	var targeting = false;
	this.target;
	this.value = (_value) ?_value :0;
	damping = (_damping) ?_damping :DAMPING;
	attraction = (_attraction) ?_attraction :ATTRACTION;
	
	this.set = function(v)
	{
		//console.log(v);
		this.value = v;
	}
	this.update = function()
	{
		//console.log(this.value);
		if (targeting)
		{
			force += attraction * (this.target - this.value);      
		}
		accel = force / mass;
		vel = (vel + accel) * damping;
		this.value += vel;
		force = 0;
	}
	this.target = function(t)
	{
		targeting = true;
		this.target = t;
	}
	this.noTarget = function()
	{
		targeting = false;
	}
}