使用OpenGL在Unity中画一个框

转载自：http://blog.csdn.net/xv_ly15/article/details/9047509

Unity3D使用的图形引擎是DirectX，OpenGL和自带的APi（Wii）

我们这里使用OpenGL的渲染方式



代码：

（使用过OpenGl的应该相对容易理解

另外：代码中使用Shader是因为矩形框中部的透明部分需要）

using UnityEngine;
using System.Collections;

public class DrawRect : MonoBehaviour {

private Vector2 mMouseStart, mMouseEnd;
private 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;
}

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;
}
}

void OnGUI()
{
if (mBDrawMouseRect)
Draw(mMouseStart, mMouseEnd);
}

//渲染2D框
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
}
}