Line (line Renderer component)
Create a new line (right-click->effect->new line, you can also add a line Renderer component to other objects).
After adding the component, you will get a line segment renderer that is not affected by the object. You can adjust the position by changing the position of the line segment (size control The number of points, the rendering connects the points to achieve the line drawing effect)
Change the corner vertices to deal with the corners of the line turning, change the end vertices to deal with the corners of the fixed points of the line, so that the transition of the line will be smoother. Check the cycle, and the head and tail of the line will be connected. Click the first button of the scene 
tool
to get three points , drag the three points separately to change the position.
The button on the right can add points, click the mouse to add points, and if the mouse click is not loose, you can draw a line to add points