making arrow with line renderer

hi guys.
i want to make a thick arrow with this situation. when the player put a finger on phone screen tip of the arrow generate and when player drag (his/her) finger tip of the arrow stretched till a Equilateral triangle generate and after that with player dragging the arrow rectangular generate.in abbreviation firstly we have just the tip of triangle and after some dragging we have whole of arrow(tip and body).
i wish we could use different material for each two consecutive point of line renderer.