glReadPixels doesn't read depth buffer values on iOS

Question

I can\'t seem to read the depth buffer values in OpenGL ES2 on iOS 4.3

afDepthPixels = (float*)malloc(sizeof(float) * iScreenWidth * iScreenHeight);
glReadPi         


        

Answer 1

As you guess, reading the depth buffer isn't supported in ES 2.x. Per the glReadPixels man page (direct from Khronos) the only permissible values for 'format' in ES 2 are GL_ALPHA, GL_RGBA and GL_RGB.

From memory, depth textures are supported on recent versions of iOS, so it should be possible to run a pixel shader to convert a depth buffer into something you can read as RGBA if you're otherwise at a dead end.