glReadPixels(Depth_Component) 在 Android OpenGL ES20 中不起作用

Question

I use the following code to retrieve the depth buffer:

FloatBuffer pixels = ByteBuffer
    .allocateDirect(4).order(ByteOrder.nativeOrder()).asFloatBuffer();

GLES20.glReadPixels(pointx, pointy, 1, 1, 
    GLES20.GL_DEPTH_COMPONENT16, GLES20.GL_FLOAT, pixels);

Problem is, whichever point I am requesting, the pixels is giving me 0.0;

I have enabled the following in onSurfaceCreated :

GLES20.glEnable(GLES20.GL_DEPTH_TEST);
GLES20.glEnable(GLES20.GL_BLEND);
GLES20.glBlendFunc(GLES20.GL_SRC_ALPHA, GLES20.GL_ONE_MINUS_SRC_ALPHA);
GLES20.glDepthFunc(GLES20.GL_LEQUAL);
GLES20.glDepthMask(true);
GLES20.glClearColor(1, 1, 1, 1);

I've been struggling with this issue for days. Please help.

Answer 1

According to the OpenGL ES 2.0 docs, glReadPixels() doesn't support reading the depth buffer. What does glGetError() return?