Here is the effect. We want cubes that are in the foreground to be out of focus and grainy (bottom right big blob). Also, random graininess seem undesirable so a fixed graininess is preferable. All other cubes should be in focus. I do have a DOF shader working but this is more than just DOF.

I have got a very nice Gaussian blur which covers most of it. But my noise shader is less than perfect since getting the distance params aren't perfect (adding noise seems to affect the entire scene). I am using the IrrLicht engine, but I'm not sure that's relevant. I am writing hlsl shaders. So far I have been sticking to pixel shaders but I am not sure that this is possible using a shader only.

So this is what I know I have. There may other resources that I have or could easily make. A distance buffer normalizing values at the camera to 0 and infinity to 1. A noise texture. A Scene buffer. A Blurred buffer (downsampled and Gaussian blurred).

Suggestions?