gistfile1.txt

using UnityEngine;
using System.Collections;

public class dottest : MonoBehaviour {

	public Transform p1;
	public Transform p2;
	public Transform p3;

	public GUIText guiDOT;

	
	void Update () 
	{

		Vector3 perpendicular = Vector3.Cross(p1.position-p2.position,Vector3.forward);
		Vector3 targetDir = (p3.position-p1.position);

		Debug.DrawLine(p1.position,p2.position,Color.gray);


		Vector3 midpoint = Vector3.Lerp(p1.position,p2.position,0.5f);
		Debug.DrawLine(midpoint,midpoint+perpendicular.normalized,Color.white);

		float dotVal = Vector3.Dot(perpendicular.normalized,targetDir.normalized);
		if (dotVal<0)
		{
			Debug.DrawLine(p1.position,p3.position,Color.red);
			Debug.DrawLine(p2.position,p3.position,Color.red);
		}else{
			Debug.DrawLine(p1.position,p3.position,Color.green);
			Debug.DrawLine(p2.position,p3.position,Color.green);

		}


		guiDOT.text = "DOT: "+dotVal;

	}
}