GL example 1

using UnityEngine;
using System.Collections;

public class joint
{
    public Vector3 org;
    public Vector3 end;
}

public class example : MonoBehaviour
{
    Event e;
    private Vector3 orgPos;
    private Vector3 endPos;
    private bool canDrawLines = false;
    ArrayList posAL;
    ArrayList temppos;
    public Material lineMaterial;

    void Start ()
    {
        temppos = new ArrayList ();
        posAL = new  ArrayList ();
    }

    void Update ()
    {
        if (Input.GetMouseButton (0)) {
            canDrawLines = true;
        }
        if (e.type != null & canDrawLines) {
            if (e.type == EventType.MouseDown) {
                orgPos = Input.mousePosition;
                endPos = Input.mousePosition;  

            }
            if (e.type == EventType.MouseDrag) {
                endPos = Input.mousePosition;
                //鼠标位置信息存入数组
                temppos.Add (Input.mousePosition);
                GLDrawLine (orgPos, endPos);
                orgPos = Input.mousePosition;
                print (temppos.Count);
            }
            if (e.type == EventType.MouseUp) {
                // orgPos=Input.mousePosition;
                endPos = Input.mousePosition;
            }
        }  

    }

    void GLDrawLine (Vector3 beg, Vector3 end)
    {
        if (!canDrawLines)
            return;
        GL.PushMatrix ();
        GL.LoadOrtho ();  

        beg.x = beg.x / Screen.width;
        end.x = end.x / Screen.width;
        beg.y = beg.y / Screen.height;
        end.y = end.y / Screen.height;
        joint tmpJoint = new joint ();
        tmpJoint.org = beg;
        tmpJoint.end = end;  

        posAL.Add (tmpJoint);  

        lineMaterial.SetPass (0);
        GL.Begin (GL.LINES);
        GL.Color (new Color (1, 1, 1, 0.5f));
        for (int i= 0; i<posAL.Count; i++) {
            joint tj = (joint)posAL [i];
            Vector3 tmpBeg = tj.org;
            Vector3 tmpEnd = tj.end;
            GL.Vertex3 (tmpBeg.x, tmpBeg.y, tmpBeg.z);
            GL.Vertex3 (tmpEnd.x, tmpEnd.y, tmpEnd.z);
        }
        GL.End ();
        GL.PopMatrix ();
    }

    void OnGUI ()
    {
        e = Event.current;  

        if (GUI.Button (new  Rect (150, 0, 100, 50), "End Lines")) {
            ClearLines ();
        }
    }

    void ClearLines ()
    {
        canDrawLines = false;
        posAL.Clear ();
    }

    void OnPostRender ()
    {
        GLDrawLine (orgPos, endPos);
    }
}