How can I access the smaller blurred textures generated for the default bloom to create new post process effects without re-computing them myself?
Bloom can be implemented with a single Gaussian blur. For better quality, we combine multiple Gaussian blurs with different radius. For better performance, we do the very wide blurs in much lower resolution. In UE3, we had 3 Gaussian blurs in the resolution 1/4, 1/8, and 1/16. We now have multiple blurs name Blur1 to 5 in the resolution 1/2 (Blur1) to 1/32 (Blur5).
from Bloom | Unreal Engine Documentation
I’d like to know this myself. Specifically for translucent objects and particle systems where I want to blur the background without having to inefficiently recompute things that already exist.
I know another thread mentioned that the bloom was actually 1 frame behind, but that would still be totally fine.
If you use a Post Process Material Before the Tonemapper, PostProcessInput0 - 1 will return everything that is a candidate for bloom.
You could render this to a renderTarget with a quater Resolution and could use this as your own “bloom” in the Post Process.
Looks like this needs a bump - lacking any way to do a custom bloom with reasonable performance has gotten in the way several times over the past few months.
@TrumpetPro There is no way at all to access the downsample chain generated for the bloom in UE’s vanilla version, you need the source code, what are you looking gets trigger in the PostProcessing.cpp check for the AddBloomPass and AddBloomSetupPass functions, Right before that check how they are using a class called FSceneDownsampleChain that’s the responsable of the downsample generation, it is pretty straight forward. Now unfortunately you will need a high level of skill since as you might guess that is not something a regular user should be touching.
Here is an example I did a while ago for my company of an anamorphic stylized bloom:
