Problems using FBO's in ES 2

I’m working with creating a histogram overlay. I created a shader witch generates a 8x8 histogram. I would like to draw it as a tiny overlay in the corner of the screen as a realtime feature of a videostream. Everything work fine when working on screen. I render local histograms all over then picture and then reduce them with another shader and finally reads back it to the CPU memory. Then I draw an overlay and renders it back to the screen.

The problems starts when using a FBO. It works great when rendering but finally I want to read back data from the FBO to the CPU memory. In ES 2.0 specification GetTexImage(…) isn’t supported and readBuffer(…) is also gone. When working online readPixels(…) works but I won’t work with offScreen rendering. readPixels(…) works for off screen pBuffers but I really want to use FBO.

I’m working with the Imagination simulator. Maybe there will be some extensions?

best regards,
Fredrik Berglund

ReadPixels is supposed to read from the currently bound framebuffer. If this doesn’t work there is a bug in the emulator library, and we’ll try to fix it as soon as possible.

Note however that pixel readback can cause substantial slowdowns because it requires synchronization between CPU and GPU.

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