我们正在 Nexus 10 上使用 OpenGL ES 2.0 开发动态壁纸。

动态壁纸使用 2 个小型 (128x128) 外部帧缓冲区在它们之间进行乒乓渲染以模糊图像。

虽然这在任何设备上都运行良好(即使在旧的 Motorola Milestone 上)，但 Nexus 10 存在一个奇怪的问题。仅当设备处于横向时才有效。如果设备在任何其他位置(90、180 或 270 度)旋转，则帧缓冲区只有清晰的颜色。我已将 glClearColor 设置为红色，因此可以清楚地看到这些帧缓冲区已被清除但没有任何渲染。

我已经在 Tegra 2、Tegra 3、Adreno 200、Adreno 320、2 个 PowerVR GPU 上对其进行了测试，它运行良好。

这看起来像是一些奇怪的驱动程序错误，但也可能是 Mali 驱动程序的一些细节。请指教。

代码摘录。

初始化帧缓冲区:

private void initBloomStuff() {
    mBloomTextureID = loadTexture("textures/empty128.png");
    mBloomVertTextureID = loadTexture("textures/empty128.png");

    mBloomFBHeight = 128;
    mBloomFBWidth = 128;

    float blurSize = 1.0f;

    // Texel offset for blur filter kernel
    m_fTexelOffset = 1.0f / mBloomFBWidth / blurSize;

    ByteBuffer tmpFB, tmpRB;
    IntBuffer handle, renderbuffers;
    int result;

    tmpFB = ByteBuffer.allocateDirect(4);
    tmpFB.order(ByteOrder.nativeOrder());
    handle = tmpFB.asIntBuffer();
    GLES20.glGenFramebuffers(1, handle);
    framebufferHandle = handle.get(0);
    GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, mBloomTextureID);
    GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, framebufferHandle);
    GLES20.glFramebufferTexture2D(GLES20.GL_FRAMEBUFFER, GLES20.GL_COLOR_ATTACHMENT0, GLES20.GL_TEXTURE_2D, mBloomTextureID, 0);

    checkGlError("FB 1");
    tmpRB = ByteBuffer.allocateDirect(4);
    renderbuffers = tmpRB.asIntBuffer();
    GLES20.glGenRenderbuffers(1, renderbuffers);
    checkGlError("FB 1 - glGenRenderbuffers");
    depthbufferHandle = renderbuffers.get(0);
    GLES20.glBindRenderbuffer(GLES20.GL_RENDERBUFFER, depthbufferHandle);
    checkGlError("FB 1 - glBindRenderbuffer");
    GLES20.glRenderbufferStorage(GLES20.GL_RENDERBUFFER, GLES20.GL_DEPTH_COMPONENT16, mBloomFBWidth, mBloomFBHeight);
    checkGlError("FB 1 - glRenderbufferStorage");
    GLES20.glFramebufferRenderbuffer(GLES20.GL_FRAMEBUFFER, GLES20.GL_DEPTH_ATTACHMENT, GLES20.GL_RENDERBUFFER, depthbufferHandle);
    checkGlError("FB 1 - glFramebufferRenderbuffer");

    result = GLES20.glCheckFramebufferStatus(GLES20.GL_FRAMEBUFFER);
    if (result != GLES20.GL_FRAMEBUFFER_COMPLETE) {
        Log.d(TAG, "Error creating framebufer 1: " + result);
    } else {
        Log.d(TAG, "Created framebufer 1: " + result);
    }

    GLES20.glBindRenderbuffer(GLES20.GL_RENDERBUFFER, 0);
    GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, 0);
    GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, 0);

    tmpFB = ByteBuffer.allocateDirect(4);
    tmpFB.order(ByteOrder.nativeOrder());
    handle = tmpFB.asIntBuffer();
    GLES20.glGenFramebuffers(1, handle);
    framebufferVertHandle = handle.get(0);
    GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, mBloomVertTextureID);
    GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, framebufferVertHandle);
    GLES20.glFramebufferTexture2D(GLES20.GL_FRAMEBUFFER, GLES20.GL_COLOR_ATTACHMENT0, GLES20.GL_TEXTURE_2D, mBloomVertTextureID, 0);

    checkGlError("FB 2");
    tmpRB = ByteBuffer.allocateDirect(4);
    renderbuffers = tmpRB.asIntBuffer();
    GLES20.glGenRenderbuffers(1, renderbuffers);
    checkGlError("FB 2 - glGenRenderbuffers");
    depthbufferVertHandle = renderbuffers.get(0);
    GLES20.glBindRenderbuffer(GLES20.GL_RENDERBUFFER, depthbufferVertHandle);
    checkGlError("FB 2 - glBindRenderbuffer");
    GLES20.glRenderbufferStorage(GLES20.GL_RENDERBUFFER, GLES20.GL_DEPTH_COMPONENT16, mBloomFBWidth, mBloomFBHeight);
    checkGlError("FB 2 - glRenderbufferStorage");
    GLES20.glFramebufferRenderbuffer(GLES20.GL_FRAMEBUFFER, GLES20.GL_DEPTH_ATTACHMENT, GLES20.GL_RENDERBUFFER, depthbufferVertHandle);
    checkGlError("FB 2 - glFramebufferRenderbuffer");

    result = GLES20.glCheckFramebufferStatus(GLES20.GL_FRAMEBUFFER);
    if (result != GLES20.GL_FRAMEBUFFER_COMPLETE) {
        Log.d(TAG, "Error creating framebufer 2: " + result);
    } else {
        Log.d(TAG, "Created framebufer 2: " + result);
    }

    GLES20.glBindRenderbuffer(GLES20.GL_RENDERBUFFER, 0);
    GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, 0);
    GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, 0);

    mTriangleVerticesVignette = ByteBuffer.allocateDirect(mQuadTriangles.length * FLOAT_SIZE_BYTES).order(ByteOrder.nativeOrder()).asFloatBuffer();
    mTriangleVerticesVignette.put(mQuadTriangles).position(0);
}

渲染到 FB:

    GLES20.glUseProgram(mProgram);
    GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, mStemTextureID);
    drawBird();
    GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, mSphereTextureID);
    drawSphere();

    GLES20.glViewport(0, 0, mBloomFBWidth, mBloomFBHeight);
    GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, framebufferHandle);
    // GLES20.glBindRenderbuffer(GLES20.GL_FRAMEBUFFER, depthbufferHandle);

    GLES20.glClearColor(1.0f, 0.5f, 0.5f, 1.0f);
    GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT);
    GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, mStemTextureID);
    drawBird();
    GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, mSphereTextureID);
    drawSphere();

    GLES20.glViewport(0, 0, screenWidth, screenHeight);
    GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, 0);
    // GLES20.glBindRenderbuffer(GLES20.GL_FRAMEBUFFER, 0); 

在 2 个 FB 之间进行乒乓渲染以模糊图像:

    GLES20.glUseProgram(mBloomProgram);
    GLES20.glUniform1i(mBloom_sTexture, 0);
    GLES20.glUniform1f(mBloom_bloomFactor, 0.8f);

    GLES20.glActiveTexture(GL10.GL_TEXTURE0);
    GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, mBloomTextureID);
    GLES20.glViewport(0, 0, mBloomFBWidth, mBloomFBHeight);
    GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, framebufferVertHandle);
    GLES20.glUniform1f(mBloom_TexelOffsetX, m_fTexelOffset);
    GLES20.glUniform1f(mBloom_TexelOffsetY, 0.0f);
    GLES20.glActiveTexture(GL10.GL_TEXTURE0);
    GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, mBloomTextureID);
    GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT);
    drawBloom();
    GLES20.glViewport(0, 0, screenWidth, screenHeight);
    GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, 0);

    GLES20.glActiveTexture(GL10.GL_TEXTURE0);
    GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, mBloomVertTextureID);
    GLES20.glViewport(0, 0, mBloomFBWidth, mBloomFBHeight);
    GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, framebufferHandle);
    GLES20.glUniform1f(mBloom_TexelOffsetX, 0.0f);
    GLES20.glUniform1f(mBloom_TexelOffsetY, m_fTexelOffset);
    GLES20.glActiveTexture(GL10.GL_TEXTURE0);
    GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, mBloomVertTextureID);
    GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT);
    drawBloom();
    GLES20.glViewport(0, 0, screenWidth, screenHeight);
    GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, 0);

    GLES20.glActiveTexture(GL10.GL_TEXTURE0);
    GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, mBloomTextureID);
    GLES20.glViewport(0, 0, mBloomFBWidth, mBloomFBHeight);
    GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, framebufferVertHandle);
    GLES20.glUniform1f(mBloom_TexelOffsetX, m_fTexelOffset / 2);
    GLES20.glUniform1f(mBloom_TexelOffsetY, m_fTexelOffset / 2);
    GLES20.glActiveTexture(GL10.GL_TEXTURE0);
    GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, mBloomTextureID);
    GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT);
    drawBloom();
    GLES20.glViewport(0, 0, screenWidth, screenHeight);
    GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, 0); 

测试应用程序以重现错误

您可以在这里下载测试 APK:https://dl.dropboxusercontent.com/u/7197208/LiveWallpaperAnimTest.apk 这是一个动态壁纸应用程序，安装它并选择“测试”动态壁纸(有一个带玫瑰的图标)。

如您所见，在默认横向模式下，您会在鸟周围看到一些“光晕”效果，这是通过 2 个帧缓冲区之间的乒乓渲染实现的。在任何其他设备方向上它都不起作用，并用清晰的颜色(红色)填充 FB。

附加链接

我也已将此问题发布到 Mali Developer Center 和 Google Code:

http://forums.arm.com/index.php?/topic/16894-nexus-10-render-to-external-rendertarget-works-only-in-landscape/

http://code.google.com/p/android/issues/detail?id=57391

最佳答案

Mali 驱动程序支持团队确认这是一个驱动程序错误，并将在下一个驱动程序版本中修复它。作为临时解决方法，他们建议在 glBindFramebuffer 之后调用 glViewport。 此解决方法有效 - 在更改调用顺序后，我设法实现了正确的渲染。

一旦固定驱动程序可用，我已建议 Google 联系 ARM 以包含用于 Nexus 10 的固定 OpenGL ES 驱动程序。如果有人愿意让这一切更快发生，您可以在 Android 错误跟踪器中给问题加注星标:http://code.google.com/p/android/issues/detail?id=57391

指向我已提交此问题的 Mali 开发人员中心论坛的链接: http://forums.arm.com/index.php?/topic/16894-nexus-10-render-to-external-rendertarget-works-only-in-landscape/

由于此驱动bug已被ARM验证确认，请您去star Android issue #57391而不是投票给这个 SO 问题。希望这会迫使谷歌关注问题并发布固件更新，让 Nexus 10 变得更好。这就是我为这个问题分配赏金的原因。

编辑。这个错误终于在 Android 4.4 中得到修复。

关于android - Nexus 10 - 渲染到外部渲染目标仅适用于横向，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/17403197/