Real-time translucency effect While rendering my scene with OpenGL, I sometimes add an overlay which contains information, settings and a few draggable items. Currently, the overlay has a slightly transparent background to make text easily readable while still allowing the scene to shine through and to let the user see the scene behind/through the overlay.

I would like to replace the transparent background with a translucent background, which (as far as I know) requires the clear image of the scene to be heavily blurred*. And especially on mobile devices (e.g. iPad) with high resolutions and limited processing power, lots of texture lookups and real-time rendering don't work well together.

Is there a way to make real-time translucency feasible on mobile devices like the iPad? Or is there a way to avoid the need to heavily blur the scene in every frame?

Edit:

As suggested in the comments, here is an image I just found in the Wikipedia that describes the difference between transparency (right column) and translucency (middle column). 



(Image source: Wikipedia)



*I know there is the two-pass blur (first blur in one and then in the other direction) to reduce texture lookups. But for translucency this still requires quite a large number of texture lookups.
I think you may want to take another look at the iOS user interface if you consider real-time blurs to be out of range of mobile hardware:




Blurs are totally in range of mobile hardware. Yes, you need a fairly large number of texture samples for a blur with a large kernel, but the texture samples are also cached very well, and you can use a separable blur, which effectively means that an MxN blur requires M + N samples, not M * N samples. You can also take advantage of hardware bilinear sampling to reduce the number of samples that your blur requires.