But I guess this is a somehow inconvinient implementation, although I saw it somewhere in the internet already for CG (search for GPU implementation of Gaussian / Laplace pyramid or similar). An alternative could be a rotated poisson filter disc with 12 samples or so, while the disc is always 5x5 pixel big or so in screen space, maybe with applied jittering. I saw such an approach for dynamically sized DOF and I guess it should work for your case, too.
I just need a cheap and good looking blur
For now, I am going with downsampling to 1/8th resolution, applying a box blur with a kernel size of 5 and doing the same again on 1/4th resolution to get rid of blocky artifacts and that is blended over the final image. I should maybe use a gaussian blur to have less of a darkening effect, on the other hand a "stronger" box blur looks usually pretty good.
I also found some link where they added the results of the different blur kernels to get rid of the darkening, but in my opinion that was a bit overdone
Also, bloom is a cheap approximation to light scattering in the lenses of the camera or alternatively the human eye. If you want to do it somewhat physically plausible you have to add the blur before tonemapping to the _full_ HDR scene, without any bright pass - the amount of scattering is not influenced by the amount of photons, of course.
Okay, but then things will look very blurry/foggy unless I keep the bloom at a minimum, but then I don´t really need it at all and I am a big fan of bright parts covering everything on the screen with their bloom halos
(bloom everywhere, very low white point and low exposure :P)
I am fine with my solution for now
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Next up is SDSM and ESM for better shadows
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