OpenGL学习

项目中要用到OpenGL,其实就是在Android中的实时添加滤镜GPUImage

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问题来了，看源码会涉及到OpenGL ,如果不去了解一下，有点对不起作为一个开发人员，所以，本逗比，开始学习，后期遇到其他的问题，会一一列出来，就作为以后的备忘录；
1. 遇到一个很奇葩的问题，当调用GSurfaceView 的时候会出现空指针异常，后来发现原来必须调用这个方法
也就是 gl.setRenderer(new GLSurfaceView.Renderer() {}这个方法，重写他的三个方法如下：

gl.setRenderer(new GLSurfaceView.Renderer() {            public void onSurfaceCreated(GL10 gl, EGLConfig config) {                // Set the background color to black ( rgba ).                gl.glClearColor(0.0f, 0.0f, 0.0f, 0.5f);  // OpenGL docs.                // Enable Smooth Shading, default not really needed.                gl.glShadeModel(GL10.GL_SMOOTH);// OpenGL docs.                // Depth buffer setup.                gl.glClearDepthf(1.0f);// OpenGL docs.                // Enables depth testing.                gl.glEnable(GL10.GL_DEPTH_TEST);// OpenGL docs.                // The type of depth testing to do.                gl.glDepthFunc(GL10.GL_LEQUAL);// OpenGL docs.                // Really nice perspective calculations.                gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, // OpenGL docs.                        GL10.GL_NICEST);            }            public void onDrawFrame(GL10 gl) {                // Clears the screen and depth buffer.                gl.glClear(GL10.GL_COLOR_BUFFER_BIT | // OpenGL docs.                        GL10.GL_DEPTH_BUFFER_BIT);            }            public void onSurfaceChanged(GL10 gl, int width, int height) {                // Sets the current view port to the new size.                gl.glViewport(0, 0, width, height);// OpenGL docs.                // Select the projection matrix                gl.glMatrixMode(GL10.GL_PROJECTION);// OpenGL docs.                // Reset the projection matrix                gl.glLoadIdentity();// OpenGL docs.                // Calculate the aspect ratio of the window                GLU.gluPerspective(gl, 45.0f,                        (float) width / (float) height,                        0.1f, 100.0f);                // Select the modelview matrix                gl.glMatrixMode(GL10.GL_MODELVIEW);// OpenGL docs.                // Reset the modelview matrix                gl.glLoadIdentity();// OpenGL docs.            }});