//计算屏幕点击处，和3D空间中的线段，在屏幕空间中的最短距离
        public static float DetectClickOnLine(Camera camera,Vector3 p1, Vector3 p2)
        {
            var v1 = camera.WorldToScreenPoint(p1);
            var v2 =camera.WorldToScreenPoint(p2);
            Vector2 point = Input.mousePosition;
            
            //计算点到直线的距离
            var xDis = v2.x - v1.x;
            var yDis = v2.y - v1.y;
            var dx = point.x - v1.x;
            var dy = point.y - v1.y;
            var d = xDis * xDis + yDis * yDis;
            var t = xDis * dx + yDis * dy;

            if (d > 0)
                t /= d;

            if (t < 0)
                t = 0;
            else if (t > 1)
                t = 1;

            dx = v1.x + t * xDis - point.x;
            dy = v1.y + t * yDis - point.y;
            return Mathf.Sqrt(dx * dx + dy * dy);
        }