I would like to blur the background in an image. If I go tweaking the actual HDRI in the world material, it will add HUGE to render times. If I, instead, use an alpha background (film:transparent) then use the compositor to blur an HDRI as a background, then I can save tons of render time. The problem is that the HDRI background is projected as a flat image, rather than a dynamic image that rotates it's view as the camera moves.
