如果配合UI做渲染，那么需要把canvas改为 scree space - camera 类型，否则在ui上的linerenderer无法和ui融合
LineRenderer line;
line = gameObject.AddComponent<LineRenderer>();
line.startColor = Color.white;
line.endColor = Color.yellow;
line.startWidth = 30f;
line.endWidth = 0f;
line.useWorldSpace = false;
addPot(new Vector3());
addPot(to_target.transform.position-transform.position);
void addPot(Vector3 pot){
pots.Add(pot);
line.positionCount++;
line.SetPosition(line.positionCount-1,pot);
}
