CGQ/Assets/Scripts/NewBehaviourScript.cs

using UnityEngine;
using System.Collections;
public class NewBehaviourScript : MonoBehaviour
{
    public Vector2 mMouseStart, mMouseEnd;
    public bool mBDrawMouseRect;

    private Material rectMat = null;//画线的材质不设定系统会用当前材质画线 结果不可控 

   

    void Start()
    {

        mBDrawMouseRect = false;

        rectMat = new Material("Shader \"Lines/Colored Blended\" {" +
                               "SubShader { Pass { " +
                               "    Blend SrcAlpha OneMinusSrcAlpha " +
                               "    ZWrite Off Cull Off Fog { Mode Off } " +
                               "    BindChannels {" +
                               "      Bind \"vertex\", vertex Bind \"color\", color }" +
                               "} } }");//生成画线的材质 
        rectMat.hideFlags = HideFlags.HideAndDontSave;
        rectMat.shader.hideFlags = HideFlags.HideAndDontSave;
    } //Unity3D教程手册：www.unitymanual.com

    //void Update()
    //{
    //    if (Input.GetMouseButtonDown(0))
    //    //按下鼠标左键 
    //    {
    //        Vector3 mousePosition = Input.mousePosition;
    //        mMouseStart = new Vector2(mousePosition.x, mousePosition.y);
    //    }

    //    if (Input.GetMouseButton(0))
    //    //持续按下鼠标左键 
    //    {
    //        mBDrawMouseRect = true;
    //        Vector3 mousePosition = Input.mousePosition;
    //        mMouseEnd = new Vector2(mousePosition.x, mousePosition.y);
    //    }

    //    if (Input.GetMouseButtonUp(0))
    //    {
    //        mBDrawMouseRect = false;
    //    }
    //}
    //Unity3D教程手册：www.unitymanual.com
    void OnGUI()
    {
        if (mBDrawMouseRect)
            Draw(mMouseStart, mMouseEnd);
    }

    //渲染2D框 
   public void Draw(Vector2 start, Vector2 end)
    {
        rectMat.SetPass(0);

        GL.PushMatrix();//保存摄像机变换矩阵 

        Color clr = Color.green;
        clr.a = 0.1f;

        GL.LoadPixelMatrix();//设置用屏幕坐标绘图 
                             //透明框 
        GL.Begin(GL.QUADS);
        GL.Color(clr);
        GL.Vertex3(start.x, start.y, 0);
        GL.Vertex3(end.x, start.y, 0);
        GL.Vertex3(end.x, end.y, 0);
        GL.Vertex3(start.x, end.y, 0);
        GL.End();

        //线 
        //上 
        GL.Begin(GL.LINES);
        GL.Color(Color.green);
        GL.Vertex3(start.x, start.y, 0);
        GL.Vertex3(end.x, start.y, 0);
        GL.End();

        //下 
        GL.Begin(GL.LINES);
        GL.Color(Color.green);
        GL.Vertex3(start.x, end.y, 0);
        GL.Vertex3(end.x, end.y, 0);
        GL.End();

        //左 
        GL.Begin(GL.LINES);
        GL.Color(Color.green);
        GL.Vertex3(start.x, start.y, 0);
        GL.Vertex3(start.x, end.y, 0);
        GL.End();

        //右 
        GL.Begin(GL.LINES);
        GL.Color(Color.green);
        GL.Vertex3(end.x, start.y, 0);
        GL.Vertex3(end.x, end.y, 0);
        GL.End();

        GL.PopMatrix();//还原 
    }
}