Hi everyone!
I wanted to share a response I posted in another thread that’s very closely related to this topic explaining how to achieve this effect in UE5, just in case it’s helpful.
Probably not the perfect solution due to the engine constraints, but it’s a solution nonetheless. 
As has already been mentioned, these kinds of effects can be relatively expensive, but every game has its own eye-candy not so cheap things. I’ve also been playing Path of Exile 2 lately and it looks like these blurring effects are definitely something they’re going for a lot.
Obviously, one of the advantages of a custom engine (as PoE2 has) is being able to build more optimally whatever rendering pipeline your game needs. But that said, here are a few general tips:
- Make your blur code as non-dynamic as possible. Use constant values, data tables, unroll loops, etc. This will help the compiler to optimize the operations the GPU has to make.
- Use a low resolution scene texture/buffer. You are going to blur the scene anyway so there is no point in having super high res data for this especifically.
- Lower the samples as much as posible. You can get pretty good results anyway if you do some in-between operations. For example, lerping the original and offseted UVs with a dithering noise. This is a comparison of a 4 sampled blur with no noise and with noise applied:
