OpenGl入门

<uses-feature android:glEsVersion="0x00020000" android:required="true" />

public class GLView extends GLSurfaceView {

    public GLView(Context context) {
        super(context);
    }

    public GLView(Context context, AttributeSet attrs) {
        super(context, attrs);
        setEGLContextClientVersion(2);
        setRenderer(new GLRander(this));
        setRenderMode(GLSurfaceView.RENDERMODE_WHEN_DIRTY);
    }
}

public class GLRander implements GLSurfaceView.Renderer {
    protected View mView;
    Triangle mTriangle;
    public GLRander(View view) {
        mView = view;
    }

    @Override
    public void onSurfaceCreated(GL10 gl, EGLConfig config) {
        GLES20.glClearColor(0, 0, 0, 0);
        mTriangle = new Triangle();
    }

    @Override
    public void onSurfaceChanged(GL10 gl, int width, int height) {
        mTriangle.onSurfaceChanged(gl, width, height);
    }

    /**
     * 该方法不断被调用
     */
    @Override
    public void onDrawFrame(GL10 gl) {
        GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT|GLES20.GL_DEPTH_BUFFER_BIT);
        mTriangle.onDrawFrame(gl);
    }
}

public class Triangle {

    /**
     * 三个顶点
     */
    static float triangleCoords[] = {
            0.5f, 0.5f, 0.0f,
            -0.5f, -0.5f, 0.0f,
            0.5f, -0.5f, 0.0f,
    };

    /**
     * 管道
     */
    private FloatBuffer vertexBuffer;

    /**
     * 顶点着色器
     */
    private String vertextShaderCode = "attribute vec4 vPosition;\n" +
            "uniform mat4 vMatrix;\n" +
            "void main(){" +
            "gl_Position=vMatrix*vPosition;" +
            "}";

    /**
     * 片元着色器
     */
    private final String fragmentShaderCode = "precision mediump float;\n" +
            "uniform  vec4 vColor;\n" +
            "void main(){\n" +
            "gl_FragColor=vColor;\t\n" +
            "}";

    int mProgram;

    public Triangle(){
        ByteBuffer bb = ByteBuffer.allocateDirect(triangleCoords.length * 4);
        bb.order(ByteOrder.nativeOrder());
        vertexBuffer=bb.asFloatBuffer();
//        把顶点  推送 给GPU
        vertexBuffer.put(triangleCoords);
        vertexBuffer.position(0);

        //创建顶点着色器 并在GPU中编译
        int shader = GLES20.glCreateShader(GLES20.GL_VERTEX_SHADER);
        GLES20.glShaderSource(shader,vertextShaderCode);
        //编译顶点着色器
        GLES20.glCompileShader(shader);

        //创建片元着色器 并在GPU中编译
        int fragmentShader = GLES20.glCreateShader(GLES20.GL_FRAGMENT_SHADER);
        GLES20.glShaderSource(fragmentShader,fragmentShaderCode);
        //编译片元着色器
        GLES20.glCompileShader(fragmentShader);

        //将顶点着色器和片元着色器放到统一的管理器中进行管理
        mProgram = GLES20.glCreateProgram();
        GLES20.glAttachShader(mProgram,shader);
        GLES20.glAttachShader(mProgram,fragmentShader);

        //连接到着色器程序
        GLES20.glLinkProgram(mProgram);
    }
    public void onSurfaceChanged(GL10 gl, int width, int height) {
         //计算宽高比
        float ratio=(float)width/height;
        //投影矩阵
        Matrix.frustumM(mProjectMatrix, 0, -ratio, ratio, -1, 1, 3, 120);
        //相机
        Matrix.setLookAtM(mViewMatrix, 
                ////摄像机的坐标
                0, 0, 0, 7,
                //目标物的中心坐标
                0f, 0f, 0f,
                //相机方向
                0f, 1f, 0f);
        //计算变换矩阵
        Matrix.multiplyMM(mMVPMatrix,0,mProjectMatrix,0,mViewMatrix,0);
    }

    /**
     * rgba
     */
    float color[] = { 1.0f, 1.0f, 1.0f, 1.0f };
    private float[] mViewMatrix=new float[16];
    private float[] mProjectMatrix=new float[16];
    private float[] mMVPMatrix=new float[16];
    public void onDrawFrame(GL10 gl) {
        //开始渲染
        //拿到总的程序
        GLES20.glUseProgram(mProgram);
        //拿到vPosition的地址
        int mPositionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition");
        //设置缩放
        int mMatrixHandler = GLES20.glGetUniformLocation(mProgram, "vMatrix");
        GLES20.glUniformMatrix4fv(mMatrixHandler,1,false,mMVPMatrix,0);
        //允许对这个地址进行读写
        GLES20.glEnableVertexAttribArray(mPositionHandle);
        //给顶点着色器赋值
        GLES20.glVertexAttribPointer(mPositionHandle,3,
                GLES20.GL_FLOAT,false,3*4,vertexBuffer);

        //给片元着色器赋值
        int mColorHandle = GLES20.glGetUniformLocation(mProgram,"vColor");
        GLES20.glUniform4fv(mColorHandle,1,color,0);
        //开始绘制
        GLES20.glDrawArrays(GLES20.GL_TRIANGLES,0,3);
        //关闭读写
        GLES20.glDisableVertexAttribArray(mPositionHandle);
    }
}