基于Android的OpenGL ES 2.0学习笔记（1）

之前大概接触过OpenGL ES 1.0，最近买了本书打算学习一下2.0的相关知识。本来以为顶多是多了一些API而已，结果真正学起来才发现用法完全不一样。最大的不同还是多了shader这么一个概念，目前我也没法完全理解shader是什么，只能在学习的过程中慢慢理解。不过基本的东西还都没变，点，线，三角等等

首先要使用es2.0的话需要先在manifest文件里声明

以下为Activity的代码

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // 隐藏标题栏
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);

        mPoint = new CZPoint();
        // 初始化GLSurfaceView
        GLSurfaceView glSurfaceView = new GLSurfaceView(this);
        glSurfaceView.setEGLContextClientVersion(2);
        glSurfaceView.setRenderer(new CZRenderer(mPoint));
        setContentView(glSurfaceView);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        // 获取touch的事件
        float x = event.getX();
        float y = event.getY();
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                mPoint.setPosition(x * 2 / CZRenderer.width - 1.0f, 1.0f - y * 2 / CZRenderer.height);
                mPoint.setColor(0.0f, 1.0f, 0.0f, 1.0f);
                break;
            case MotionEvent.ACTION_UP:
                mPoint.setPosition(x * 2 / CZRenderer.width - 1.0f, 1.0f - y * 2 / CZRenderer.height);
                mPoint.setColor(0.0f, 0.0f, 1.0f, 1.0f);
                break;
        }
        return super.onTouchEvent(event);
    }

为了以后的扩展性定义了一个接口：

public interface ICZgles {
    void init(int program, int vertexShader, int fragmentShader);
    String getVertexShader();
    String getFragmentShader();
    void draw();
}

以下为顶点相关的类，其中涉及到glsl语言，以后还得慢慢学

public class CZPoint implements ICZgles {
    private static final String TAG = "CZPoint";

    private static final String VERTEX_SHADER
            = "attribute vec4 a_Position;"
            + "void main() {"
            + "    gl_Position = a_Position;"
            + "    gl_PointSize = 50.0;"
            + "}";
    private static final String FRAGMENT_SHADER
            = "precision mediump float;"
            + "uniform vec4 u_FragmentColor;"
            + "void main() {"
            + "    gl_FragColor = u_FragmentColor;"
            + "}";

    private int mAPosition;
    private int mUFragmentColor;
    private float[] mPosition = {0.0f, 0.0f};
    private float[] mColor = {1.0f, 0.0f, 0.0f, 1.0f};

    CZPoint() {
        Log.d(TAG, "chenzhen");
    }

    @Override
    public void init(int program, int vertexShader, int fragmentShader) {
        mAPosition = GLES20.glGetAttribLocation(program, "a_Position");
        mUFragmentColor = GLES20.glGetUniformLocation(program, "u_FragmentColor");
    }

    @Override
    public String getVertexShader() {
        return VERTEX_SHADER;
    }

    @Override
    public String getFragmentShader() {
        return FRAGMENT_SHADER;
    }

    @Override
    public void draw() {
        GLES20.glVertexAttrib3f(mAPosition, mPosition[0], mPosition[1], 0.0f);
        GLES20.glUniform4f(mUFragmentColor, mColor[0], mColor[1], mColor[2], mColor[3]);
        GLES20.glDrawArrays(GLES20.GL_POINTS, 0, 1);
    }

    public void setPosition(float x, float y) {
        mPosition[0] = x;
        mPosition[1] = y;
    }

    public void setColor(float r, float g, float b, float a) {
        mColor[0] = r;
        mColor[1] = g;
        mColor[2] = b;
        mColor[3] = a;
    }
}

最后是Renderer的代码：

public class CZRenderer implements GLSurfaceView.Renderer {
    public static float width = 0;
    public static float height = 0;

    private int mProgram;
    private String mVertexShaderSource;
    private String mFragmentShaderSource;
    private ICZgles iCZ;

    public CZRenderer(ICZgles icZgles) {
        iCZ = icZgles;
        mVertexShaderSource = iCZ.getVertexShader();
        mFragmentShaderSource = iCZ.getFragmentShader();
    }

    @Override
    public void onSurfaceCreated(GL10 gl10, EGLConfig eglConfig) {
        GLES20.glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
        mProgram = GLES20.glCreateProgram();
        int vertexShader = loadShader(GLES20.GL_VERTEX_SHADER, mVertexShaderSource);
        int fragmentShader = loadShader(GLES20.GL_FRAGMENT_SHADER, mFragmentShaderSource);
        GLES20.glAttachShader(mProgram, vertexShader);
        GLES20.glAttachShader(mProgram, fragmentShader);
        GLES20.glLinkProgram(mProgram);
        GLES20.glUseProgram(mProgram);
        iCZ.init(mProgram, vertexShader, fragmentShader);
    }

    @Override
    public void onSurfaceChanged(GL10 gl10, int i, int i1) {
        GLES20.glViewport(0, 0, i, i1);
        width = i;
        height = i1;
    }

    @Override
    public void onDrawFrame(GL10 gl10) {
        GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);
        iCZ.draw();
    }

    private int loadShader(int type, String source) {
        int shader = GLES20.glCreateShader(type);
        GLES20.glShaderSource(shader, source);
        GLES20.glCompileShader(shader);
        return shader;
    }
}

针对shader多了很多api，也需要慢慢理解