顶点缓冲区VBO和索引缓冲区IBO的结合使用

	virtual void onInit()
	{
		//清空窗口为黑色
		glClearColor(0,0,0,1);
		//设置视口的位置和大小--尝试改变视口的位置和大小
		glViewport(0,0,(GLint)_winWidth,(GLint)_winHeight);

		//创建VBO-顶点缓冲区
		glGenBuffers(1, &_vertexId);//若创建多个，第二个参数应该是数组
		//绑定并指定buffer类型为VBO
		glBindBuffer(GL_ARRAY_BUFFER,_vertexId);

		float   x = 100;
		float   y = 100;
		float   w = 100;
		float   h = 100;
		CELL::float2  pos[] =
		{
			CELL::float2(x, y),
			CELL::float2(x + w, y),
			CELL::float2(x + w, y + h),
			CELL::float2(y, y + h),

		};
		//将内存中的顶点数据传送进显存
		glBufferData(GL_ARRAY_BUFFER,sizeof(pos),pos,GL_STATIC_DRAW);
		//切换状态
		glBindBuffer(GL_ARRAY_BUFFER, 0);
		//创建索引缓冲区
		glGenBuffers(1, &_indexId);
		glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,_indexId);
		//指定顶点索引
		unsigned short     arIndex[] =
		{
			0, 1, 2, 3, 0
		};
		//数据传递到显卡
		glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(arIndex), arIndex, GL_STATIC_DRAW);
		//切换状态
		glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,0);
	}

渲染

virtual void render()
	{
		//清除深度缓冲和颜色缓冲
		glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
		//指定视口大小
		glViewport(0,0,_winWidth,_winHeight);

		//创建一个投影矩阵
		CELL::matrix4 screenProj = CELL::ortho<float>(0, float(_winWidth), float(_winHeight), 0, -100.0f, 100);
		glBindBuffer(GL_ARRAY_BUFFER,_vertexId);
		_shader.begin();//启用顶点相关属性
		{
			glUniformMatrix4fv(_shader._MVP,1,false,screenProj.data());
			glUniform4f(_shader._color,1,0,0,1);
			glVertexAttribPointer(_shader._position, 2, GL_FLOAT, false, sizeof(CELL::float2), 0);
			unsigned short     arIndex[] =
			{
				0, 1, 2, 3, 0
			};
			glDrawElements(GL_LINE_STRIP,5,GL_UNSIGNED_SHORT,arIndex);
		}
		_shader.end();//关闭顶点相关属性
		glBindBuffer(GL_ARRAY_BUFFER,0);
		eglSwapBuffers(_display,_surface);
	}