Unity 拖动惯性效果

缓冲时间可以自己调
using UnityEngine;
using System.Collections;

public class Drag : MonoBehaviour
{
private Vector3 _screenPoint;
private Vector3 _offset;
private Vector3 _curScreenPoint;
private Vector3 _curPosition;
private Vector3 _velocity;
private bool _underInertia;
private float _time = 0.0f;
public float SmoothTime;

void Update()
{
if(_underInertia && _time <= SmoothTime)
{
transform.position += _velocity;
_velocity = Vector3.Lerp(_velocity, Vector3.zero, _time);
_time += Time.smoothDeltaTime;
}
else
{
_underInertia = false;
_time = 0.0f;
}
}
void OnMouseDown()
{
_screenPoint = Camera.main.WorldToScreenPoint(gameObject.transform.position);
_offset = gameObject.transform.position - Camera.main.ScreenToWorldPoint(new Vector3(Input.mousePosition.x, Input.mousePosition.y, _screenPoint.z));
//Screen.showCursor = false;
_underInertia = false;
}
void OnMouseDrag()
{
Vector3 _prevPosition = _curPosition;
_curScreenPoint = new Vector3(Input.mousePosition.x, Input.mousePosition.y, _screenPoint.z);
_curPosition = Camera.main.ScreenToWorldPoint(_curScreenPoint) + _offset;
_velocity = _curPosition - _prevPosition;
transform.position = _curPosition;
}
void OnMouseUp()
{
_underInertia = true;
//Screen.showCursor = true;
}
}