被拖动物体mesh 设为convex,is trigger为true。collider之间至少有一个rigidbody
void OnTriggerEnter(Collider collider){
if(collider.gameObject.layer==LayerMask.NameToLayer("Obstacles"))Debug.Log("Error,a obstacle!");
Renderer rd= gameObject.GetComponent<MeshRenderer> ();
rd.material.color = Color.yellow;
}
void OnTriggerExit(Collider collider){
if(collider.gameObject.layer==LayerMask.NameToLayer("Obstacles"))
Debug.Log("leaving a obstacle!");
Renderer rd= gameObject.GetComponent<MeshRenderer> ();
rd.material.color = Color.white;
}