I dont have a blur shader currently.. although i would assume some research into gaussian blurring algorithms or multi-tap blurring would be sufficient to do it. as far as the distance calculation...my plan would be to only do a subtle blur so overall all the shadows into the distance would *appear* blurrier because they are smaller and have less detail. I dont think a blur shader would allow you to assign different blurs to different pixels.. at least not a simple and fast one..