unity 物体不随相机的距离远近而变化(屏幕大小不变)

原理：

1将物体世界坐标转为屏幕坐标  计算物体所代表的屏幕宽度比例 

Start{

Vector3 v1 = Camera.main.WorldToScreenPoint(GizmoObj.transform.position);

Vector3 v2 = Camera.main.WorldToScreenPoint(GizmoObj.transform.position+ Camera.main.transform.right);

float Scale= Mathf.Abs(v2.x - v1.x);//屏幕宽度 ---》先获取默认比例下的宽度值

}

2 物体位置改变后执行  

    private void ChangeGizmoScale()     {         Debug.Log(Camera.main.transform.right);         Vector3 v1 = Camera.main.WorldToScreenPoint(GizmoObj.transform.position);         Vector3 v2 = Camera.main.WorldToScreenPoint(GizmoObj.transform.position+ Camera.main.transform.right);         float n = Scale / Mathf.Abs(v2.x - v1.x);//得到比例差

        Vector3 v3=GizmoObj.transform.localScale;

        GizmoObj.transform.localScale=new Vector3(v3.x*n,v3.y*n,v3.z*n);//改变新比例     }