OpenGL ES系列 之 基本-3：Hello,EGL

功夫羊 kongfu.yang(a)gmail.com http://www.play3d.net

注：本文中例子针对Windows CE平台编写。

OpenGL ES简化了模型描述，取消了通过在 glBegin/glEnd 之间使用大量glVertex之类的调用来逐点描述模型，统一到使用VertexArray。

下面我们就来画一个简单的物体：用三角形拼出的HELLO EGL。该物体的示意图如下：

照例，先New App：

然后设置一下项目属性：

共有三处要改的，使得该项目可以利用上如下图所示的库和头文件：

首先是头文件包含目录：

然后是库文件目录：

最后是OpenGL ES库：

OK，环境准备好了，可以写代码了。先把我们准备好的OpenGL ES初始化代码加上：

最后标记出来的那个draw()函数就是实际绘制HELLO EGL的代码了：

正如前面提过的，我们只能通过VERTEX_ARRAY批量的将模型顶点坐标发送给OpenGL ES，为此需要先glEnableClientState()以打开相关支持。为了让世界看上去更美好一点，我还用ColorArray给每个顶点指定了颜色。然后通过glVertexPointer/glColorPointer将数据发送出去，再通过glDrawArrays(GL_TRIANGLES)进行绘制。值得一提的是，目前GLES不支持GL_QUADS。 除了调用glDrawArrays()，OpenGL ES还提供了更为灵活的glDrawElements()方法，值得看一下规范里的说明。

剩下的奥密就全在数组helloVertex里了。其实它的内容已经完全表示的本文开始的那张示意图里了，建议您自己推算一下，以熟悉TRIANGLES建模。这个小小的例子也可以利用GL_TRIANG_STRIP得到很大的优化，感兴趣的可以练习一下。

代码如下：
hellomesh.h
#ifndef _HELLO_MESH_ #define _HELLO_MESH_ GLfixed helloVertex[] = { // HELLO EGL // H Float2Fixed(0.0f), Float2Fixed(0.0f), Float2Fixed(0.1f), Float2Fixed(0.0f), Float2Fixed(0.1f), Float2Fixed(0.7f), Float2Fixed(0.0f), Float2Fixed(0.0f), Float2Fixed(0.1f), Float2Fixed(0.7f), Float2Fixed(0.0f), Float2Fixed(0.7f), Float2Fixed(0.1f), Float2Fixed(0.3f), Float2Fixed(0.3f), Float2Fixed(0.3f), Float2Fixed(0.3f), Float2Fixed(0.4f), Float2Fixed(0.1f), Float2Fixed(0.3f), Float2Fixed(0.3f), Float2Fixed(0.4f), Float2Fixed(0.1f), Float2Fixed(0.4f), Float2Fixed(0.3f), Float2Fixed(0.0f), Float2Fixed(0.4f), Float2Fixed(0.0f), Float2Fixed(0.4f), Float2Fixed(0.7f), Float2Fixed(0.3f), Float2Fixed(0.0f), Float2Fixed(0.4f), Float2Fixed(0.7f), Float2Fixed(0.3f), Float2Fixed(0.7f), // E Float2Fixed(0.5f), Float2Fixed(0.0f), Float2Fixed(0.6f), Float2Fixed(0.0f), Float2Fixed(0.6f), Float2Fixed(0.7f), Float2Fixed(0.5f), Float2Fixed(0.0f), Float2Fixed(0.6f), Float2Fixed(0.7f), Float2Fixed(0.5f), Float2Fixed(0.7f), Float2Fixed(0.6f), Float2Fixed(0.0f), Float2Fixed(0.9f), Float2Fixed(0.0f), Float2Fixed(0.9f), Float2Fixed(0.1f), Float2Fixed(0.6f), Float2Fixed(0.0f), Float2Fixed(0.9f), Float2Fixed(0.1f), Float2Fixed(0.6f), Float2Fixed(0.1f), Float2Fixed(0.6f), Float2Fixed(0.3f), Float2Fixed(0.9f), Float2Fixed(0.3f), Float2Fixed(0.9f), Float2Fixed(0.4f), Float2Fixed(0.6f), Float2Fixed(0.3f), Float2Fixed(0.9f), Float2Fixed(0.4f), Float2Fixed(0.6f), Float2Fixed(0.4f), Float2Fixed(0.6f), Float2Fixed(0.6f), Float2Fixed(0.9f), Float2Fixed(0.6f), Float2Fixed(0.9f), Float2Fixed(0.7f), Float2Fixed(0.6f), Float2Fixed(0.6f), Float2Fixed(0.9f), Float2Fixed(0.7f), Float2Fixed(0.6f), Float2Fixed(0.7f), // L Float2Fixed(1.0f), Float2Fixed(0.0f), Float2Fixed(1.1f), Float2Fixed(0.0f), Float2Fixed(1.1f), Float2Fixed(0.7f), Float2Fixed(1.0f), Float2Fixed(0.0f), Float2Fixed(1.1f), Float2Fixed(0.7f), Float2Fixed(1.0f), Float2Fixed(0.7f), Float2Fixed(1.1f), Float2Fixed(0.0f), Float2Fixed(1.4f), Float2Fixed(0.0f), Float2Fixed(1.4f), Float2Fixed(0.1f), Float2Fixed(1.1f), Float2Fixed(0.0f), Float2Fixed(1.4f), Float2Fixed(0.1f), Float2Fixed(1.1f), Float2Fixed(0.1f), // L Float2Fixed(1.5f), Float2Fixed(0.0f), Float2Fixed(1.6f), Float2Fixed(0.0f), Float2Fixed(1.6f), Float2Fixed(0.7f), Float2Fixed(1.5f), Float2Fixed(0.0f), Float2Fixed(1.6f), Float2Fixed(0.7f), Float2Fixed(1.5f), Float2Fixed(0.7f), Float2Fixed(1.6f), Float2Fixed(0.0f), Float2Fixed(1.9f), Float2Fixed(0.0f), Float2Fixed(1.9f), Float2Fixed(0.1f), Float2Fixed(1.6f), Float2Fixed(0.0f), Float2Fixed(1.9f), Float2Fixed(0.1f), Float2Fixed(1.6f), Float2Fixed(0.1f), // O Float2Fixed(2.0f), Float2Fixed(0.0f), Float2Fixed(2.1f), Float2Fixed(0.0f), Float2Fixed(2.1f), Float2Fixed(0.7f), Float2Fixed(2.0f), Float2Fixed(0.0f), Float2Fixed(2.1f), Float2Fixed(0.7f), Float2Fixed(2.0f), Float2Fixed(0.7f), Float2Fixed(2.1f), Float2Fixed(0.0f), Float2Fixed(2.3f), Float2Fixed(0.0f), Float2Fixed(2.3f), Float2Fixed(0.1f), Float2Fixed(2.1f), Float2Fixed(0.0f), Float2Fixed(2.3f), Float2Fixed(0.1f), Float2Fixed(2.1f), Float2Fixed(0.1f), Float2Fixed(2.1f), Float2Fixed(0.6f), Float2Fixed(2.3f), Float2Fixed(0.6f), Float2Fixed(2.3f), Float2Fixed(0.7f), Float2Fixed(2.1f), Float2Fixed(0.6f), Float2Fixed(2.3f), Float2Fixed(0.7f), Float2Fixed(2.1f), Float2Fixed(0.7f), Float2Fixed(2.3f), Float2Fixed(0.0f), Float2Fixed(2.4f), Float2Fixed(0.0f), Float2Fixed(2.4f), Float2Fixed(0.7f), Float2Fixed(2.3f), Float2Fixed(0.0f), Float2Fixed(2.4f), Float2Fixed(0.7f), Float2Fixed(2.3f), Float2Fixed(0.7f), // E Float2Fixed(2.5f), Float2Fixed(0.0f), Float2Fixed(2.6f), Float2Fixed(0.0f), Float2Fixed(2.6f), Float2Fixed(0.7f), Float2Fixed(2.5f), Float2Fixed(0.0f), Float2Fixed(2.6f), Float2Fixed(0.7f), Float2Fixed(2.5f), Float2Fixed(0.7f), Float2Fixed(2.6f), Float2Fixed(0.0f), Float2Fixed(2.9f), Float2Fixed(0.0f), Float2Fixed(2.9f), Float2Fixed(0.1f), Float2Fixed(2.6f), Float2Fixed(0.0f), Float2Fixed(2.9f), Float2Fixed(0.1f), Float2Fixed(2.6f), Float2Fixed(0.1f), Float2Fixed(2.6f), Float2Fixed(0.3f), Float2Fixed(2.9f), Float2Fixed(0.3f), Float2Fixed(2.9f), Float2Fixed(0.4f), Float2Fixed(2.6f), Float2Fixed(0.3f), Float2Fixed(2.9f), Float2Fixed(0.4f), Float2Fixed(2.6f), Float2Fixed(0.4f), Float2Fixed(2.6f), Float2Fixed(0.6f), Float2Fixed(2.9f), Float2Fixed(0.6f), Float2Fixed(2.9f), Float2Fixed(0.7f), Float2Fixed(2.6f), Float2Fixed(0.6f), Float2Fixed(2.9f), Float2Fixed(0.7f), Float2Fixed(2.6f), Float2Fixed(0.7f), // G Float2Fixed(3.1f), Float2Fixed(0.6f), Float2Fixed(3.4f), Float2Fixed(0.6f), Float2Fixed(3.4f), Float2Fixed(0.7f), Float2Fixed(3.1f), Float2Fixed(0.6f), Float2Fixed(3.4f), Float2Fixed(0.7f), Float2Fixed(3.1f), Float2Fixed(0.7f), Float2Fixed(3.0f), Float2Fixed(0.0f), Float2Fixed(3.1f), Float2Fixed(0.0f), Float2Fixed(3.1f), Float2Fixed(0.7f), Float2Fixed(3.0f), Float2Fixed(0.0f), Float2Fixed(3.1f), Float2Fixed(0.7f), Float2Fixed(3.0f), Float2Fixed(0.7f), Float2Fixed(3.1f), Float2Fixed(0.0f), Float2Fixed(3.4f), Float2Fixed(0.0f), Float2Fixed(3.4f), Float2Fixed(0.1f), Float2Fixed(3.1f), Float2Fixed(0.0f), Float2Fixed(3.4f), Float2Fixed(0.1f), Float2Fixed(3.1f), Float2Fixed(0.1f), Float2Fixed(3.3f), Float2Fixed(0.1f), Float2Fixed(3.4f), Float2Fixed(0.1f), Float2Fixed(3.4f), Float2Fixed(0.3f), Float2Fixed(3.3f), Float2Fixed(0.1f), Float2Fixed(3.4f), Float2Fixed(0.3f), Float2Fixed(3.3f), Float2Fixed(0.3f), Float2Fixed(3.25f), Float2Fixed(0.3f), Float2Fixed(3.45f), Float2Fixed(0.3f), Float2Fixed(3.45f), Float2Fixed(0.4f), Float2Fixed(3.25f), Float2Fixed(0.3f), Float2Fixed(3.45f), Float2Fixed(0.4f), Float2Fixed(3.25f), Float2Fixed(0.4f), // L Float2Fixed(3.5f), Float2Fixed(0.0f), Float2Fixed(3.6f), Float2Fixed(0.0f), Float2Fixed(3.6f), Float2Fixed(0.7f), Float2Fixed(3.5f), Float2Fixed(0.0f), Float2Fixed(3.6f), Float2Fixed(0.7f), Float2Fixed(3.5f), Float2Fixed(0.7f), Float2Fixed(3.6f), Float2Fixed(0.0f), Float2Fixed(3.9f), Float2Fixed(0.0f), Float2Fixed(3.9f), Float2Fixed(0.1f), Float2Fixed(3.6f), Float2Fixed(0.0f), Float2Fixed(3.9f), Float2Fixed(0.1f), Float2Fixed(3.6f), Float2Fixed(0.1f) }; #define RED Float2Fixed(1.0f) , Float2Fixed(0.0f) , Float2Fixed(0.0f) , Float2Fixed(1.0f) #define GREEN Float2Fixed(0.0f) , Float2Fixed(1.0f) , Float2Fixed(0.0f) , Float2Fixed(1.0f) #define BLUE Float2Fixed(0.0f) , Float2Fixed(0.0f) , Float2Fixed(1.0f) , Float2Fixed(1.0f) float helloColor[] = { // HELLO EGL // H // 0.0,0.0, 0.1,0.0, 0.1,0.7, RED, GREEN, BLUE, // 0.0,0.0, 0.1,0.7, 0.0,0.7, RED, GREEN, BLUE, // 0.1,0.3, 0.3,0.3, 0.3,0.4, RED, GREEN, BLUE, // 0.1,0.3, 0.3,0.4, 0.1,0.4, RED, GREEN, BLUE, // 0.3,0.0, 0.4,0.0, 0.4,0.7, RED, GREEN, BLUE, // 0.3,0.0, 0.4,0.7, 0.3,0.7, RED, GREEN, BLUE, // E //0.5,0.0, 0.6,0.0, 0.6,0.7, RED, GREEN, BLUE, //0.5,0.0, 0.6,0.7, 0.5,0.7, RED, GREEN, BLUE, //0.6,0.0, 0.9,0.0, 0.9,0.1, RED, GREEN, BLUE, //0.6,0.0, 0.9,0.1, 0.6,0.1, RED, GREEN, BLUE, //0.6,0.3, 0.9,0.3, 0.9,0.4, RED, GREEN, BLUE, //0.6,0.3, 0.9,0.4, 0.6,0.4, RED, GREEN, BLUE, //0.6,0.6, 0.9,0.6, 0.9,0.7, RED, GREEN, BLUE, //0.6,0.6, 0.9,0.7, 0.6,0.7, RED, GREEN, BLUE, // L //1.0,0.0, 1.1,0.0, 1.1,0.7, RED, GREEN, BLUE, //1.0,0.0, 1.1,0.7, 1.0,0.7, RED, GREEN, BLUE, RED, GREEN, BLUE, //1.1,0.0, 1.4,0.0, 1.4,0.1, RED, GREEN, BLUE, //1.1,0.0, 1.4,0.1, 1.1,0.1, // L //1.5,0.0, 1.6,0.0, 1.6,0.7, RED, GREEN, BLUE, //1.5,0.0, 1.6,0.7, 1.5,0.7, RED, GREEN, BLUE, //1.6,0.0, 1.9,0.0, 1.9,0.1, RED, GREEN, BLUE, //1.6,0.0, 1.9,0.1, 1.6,0.1, RED, GREEN, BLUE, // O //2.0,0.0, 2.1,0.0, 2.1,0.7, RED, GREEN, BLUE, //2.0,0.0, 2.1,0.7, 2.0,0.7, RED, GREEN, BLUE, //2.1,0.0, 2.3,0.0, 2.3,0.1, RED, GREEN, BLUE, //2.1,0.0, 2.3,0.1, 2.1,0.1, RED, GREEN, BLUE, //2.1,0.6, 2.3,0.6, 2.3,0.7, RED, GREEN, BLUE, //2.1,0.6, 2.3,0.7, 2.1,0.7, RED, GREEN, BLUE, //2.3,0.0, 2.4,0.0, 2.4,0.7, RED, GREEN, BLUE, //2.3,0.0, 2.4,0.7, 2.3,0.7, RED, GREEN, BLUE, // E //2.5,0.0, 2.6,0.0, 2.6,0.7, RED, GREEN, BLUE, //2.5,0.0, 2.6,0.7, 2.5,0.7, RED, GREEN, BLUE, //2.6,0.0, 2.9,0.0, 2.9,0.1, RED, GREEN, BLUE, //2.6,0.0, 2.9,0.1, 2.6,0.1, RED, GREEN, BLUE, //2.6,0.3, 2.9,0.3, 2.9,0.4, RED, GREEN, BLUE, //2.6,0.3, 2.9,0.4, 2.6,0.4, RED, GREEN, BLUE, //2.6,0.6, 2.9,0.6, 2.9,0.7, RED, GREEN, BLUE, //2.6,0.6, 2.9,0.7, 2.6,0.7, RED, GREEN, BLUE, // G //3.1,0.6, 3.4,0.6, 3.4,0.7, RED, GREEN, BLUE, //3.1,0.6, 3.4,0.7, 3.1,0.7, RED, GREEN, BLUE, //3.0,0.0, 3.1,0.0, 3.1,0.7, RED, GREEN, BLUE, //3.0,0.0, 3.1,0.7, 3.0,0.7, RED, GREEN, BLUE, //3.1,0.0, 3.4,0.0, 3.4,0.1, RED, GREEN, BLUE, //3.1,0.0, 3.4,0.1, 3.1,0.1, RED, GREEN, BLUE, //3.3,0.1, 3.4,0.1, 3.4,0.3 RED, GREEN, BLUE, //3.3,0.1, 3.4,0.3, 3.3,0.3 RED, GREEN, BLUE, //3.25,0.3, 3.45,0.3, 3.45,0.4, RED, GREEN, BLUE, //3.25,0.3, 3.45,0.4, 3.25,0.4, RED, GREEN, BLUE, // L //3.5,0.0, 3.6,0.0, 3.6,0.7, RED, GREEN, BLUE, //3.5,0.0, 3.6,0.7, 3.5,0.7, RED, GREEN, BLUE, //3.6,0.0, 3.9,0.0, 3.9,0.1, RED, GREEN, BLUE, //3.6,0.0, 3.9,0.1, 3.6,0.1 RED, GREEN, BLUE }; #endif // _HELLO_MESH_
可能注意到里面大量调用了宏Float2Fixed，这是因为OpenGL ES 1.0 Common Lite Profile只支持定点数，不能直接使用浮点坐标。所谓定点数这里指的是16整数部份+16位小数部份的32位数，也就是OpenGL ES预定义的GLfixed类型。 将单精度浮点数转成定点数很简单，直接乘个65536再强制一下类型就行了，这也就是Float2Fixed所做的。

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