无法让 opengl ES 在 Android 上绘制任何 2D 内容

Question

这是我为了让 2D 绘图工作而编写的代码。活动、视图和渲染器均以正确的方式设置。我得到一个全黑的屏幕，但上面没有多边形。什么也没画。这快要把我逼疯了……

public class OpenGLActivity extends Activity {

    private GLSurfaceView surfaceView;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(
                WindowManager.LayoutParams.FLAG_FULLSCREEN, 
                WindowManager.LayoutParams.FLAG_FULLSCREEN
                );

        this.surfaceView = new OpenGLSurfaceView(this);
        setContentView(this.surfaceView);
    }

    @Override
    protected void onPause() {
        super.onPause();
        surfaceView.onPause();
    }

    @Override
    protected void onResume() {
        super.onResume();
        surfaceView.onResume();
    }
}

public class OpenGLSurfaceView extends GLSurfaceView {

    private OpenGLSurfaceRenderer renderer;

    public OpenGLSurfaceView(Context context) {
        super(context);
        this.renderer = new OpenGLSurfaceRenderer();
        setRenderer(renderer);
    }

}

public class OpenGLSurfaceRenderer implements Renderer {

    private FloatBuffer vertexBuffer;
    private float[] vertices = {
            0.0f, 1.0f, 0.0f,
            0.0f, 0.0f, 0.0f,
            1.0f, 1.0f, 0.0f,
            1.0f, 0.0f, 0.0f,
            0.0f, 10.0f, 0.0f,
            0.0f, 0.0f, 0.0f,
            10.0f, 10.0f, 0.0f,
            10.0f, 0.0f, 0.0f
    };

    public OpenGLSurfaceRenderer() {
        ByteBuffer byteBuffer = ByteBuffer.allocateDirect(vertices.length * (Float.SIZE >> 3));
        vertexBuffer = byteBuffer.asFloatBuffer();
        vertexBuffer.put(vertices);
        vertexBuffer.position(0);
    }

    public void onSurfaceCreated(GL10 gl, EGLConfig config) {

        gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_FASTEST);

        gl.glClearColor(0.0f, 0.0f, 0.0f, 1);
        gl.glShadeModel(GL10.GL_FLAT);
        gl.glDisable(GL10.GL_DEPTH_TEST);
        gl.glEnable(GL10.GL_TEXTURE_2D);

        gl.glDisable(GL10.GL_DITHER);
        gl.glDisable(GL10.GL_LIGHTING);

        gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
    }

    public void onDrawFrame(GL10 gl) {

        gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);
        gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer);

        gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
        gl.glColor4f(1.0f, 1.0f, 1.0f, 1.0f);

        gl.glTranslatef(0.0f, 0.0f, 0.5f);
        gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, 4);
    }

    public void onSurfaceChanged(GL10 gl, int width, int height) {

        gl.glViewport(0, 0, width, height);

        // Clear the projection matrix
        gl.glMatrixMode(GL10.GL_PROJECTION);
        gl.glLoadIdentity();

        // Set up orthographic projection mode (2D drawing)
        gl.glOrthof(0, width, height, 0, 0, 1);

        gl.glMatrixMode(GL10.GL_MODELVIEW);
        gl.glLoadIdentity();
    }

}

Answer 1

我看到四个问题：

1. glDrawArrays() 的最后一个参数应该是 8，而不是 4。这是您提供的顶点数，而不是三角形带中的三角形数。

2. 您的正交投影使您的世界单位相当于像素。前 4 个顶点描述 1 像素宽的三角形。也许您在屏幕的左下角看到了一个白色像素？

3. 每一帧都沿 Z 轴推进模型投影。 2 帧后，它将脱离视锥体。

4. 最重要的是，您没有在 ByteBuffer 上设置正确的顺序。将此行插入到您的 OpenGlRenderer() 构造函数中：

   公共 OpenGLSurfaceRenderer() {
   ByteBuffer byteBuffer = ByteBuffer.allocateDirect(vertices.length * 4);
   byteBuffer.order(ByteOrder.nativeOrder()); <------
   vertexBuffer = byteBuffer.asFloatBuffer();
   vertexBuffer.put(顶点);
   vertexBuffer.position(0);
   最重要