B ilateral smoothing anyone?

www.geeks3d.com/forums/index.php/topic,4...msg6445.html#msg6445

ufoym.com/RecursiveBF/
github.com/ufoym/RecursiveBF

This isn't a shader.

Strictly no, but the implementation can be an inspiration to maximize the performance of some BF already existing implimentations for reshade.

There's only so much to do for blurring images. One can compute it in lower resolution, make use of bilinear filtering, separate it in horizontal and vertical step. Gassing blurs are so fast already there's not much to do tbh.