Bloom Intensity at 0 disables other Post Process effects when post process quality is low

Create a first person blueprint project.

  • Set post process quality to low.

  • Select level post process volume
  • Enable gamma and bloom intensity.
  • Set gamma values to darken screen.
  • Then set bloom intensity to 0.
  • Effects from gamma (and other post process effects) is disabled when bloom intensity is at 0

Hi ,

This behavior is the same across multiple versions of the engine and appears to be intended behavior that I can see.

When using the LOW Scalability setting for Post Processing the CVar for r.Tonemapper.GrainQuantization is set to 0 whereas all other settings have it set to 1. You can see what scalability CVars are affected by the quality changes in the documentation here: Scalability Reference for Unreal Engine | Unreal Engine 5.2 Documentation

-Tim

Thank you. I somehow did not trigger it before in 4.13, but I see the same thing happens there. My bad.

Edit: r.Tonemapper.GrainQuantization is set to 0 on both LOW and MEDIUM post process quality. Not only in LOW as you say:

When using the LOW Scalability setting for Post Processing the CVar for r.Tonemapper.GrainQuantization is set to 0 whereas all other settings have it set to 1.

But the issue only happens at post process LOW, not on MEDIUM

Right, because that’s the only setting that disables that CVar. Medium - EPIC has it enabled, which is shown on the scalability page I linked.

For me 4.13 - my internal build of 4.15 all behaved the same when checking this.

In the scalability link you sent me, both sg.PostProcessQuality 0 and sg.PostProcessQuality 1 has r.Tonemapper.GrainQuantization set to 0

Yeah you’re right on that one. My bad.

Looking at 4.14 preview 1, though, there has been improvements over 4.13’s and this still appears to be intended that Gamma relies on Bloom to be enabled in some form.

In 4.13 there was a noticeable “pop” when you have Gamma values with a Bloom value between 0 and 0.0001. In 4.14 and my internal 4.15 build work exactly the same. Gamma and the other options under Color Grading also have slider values for white level now as well. With the scalability between medium and low, there is likely another cvar that is being set that’s just not mentioned in the documentation, but I’ve not looked through the source yet. If you need Low settings and this enabled, I would say as a workaround to just use a very low-value Bloom to keep the gamma.

Thank you for all your help. This was for a settings menu, and that’s why I noticed the issue. I will use your workaround. Either keep a very low value bloom, or simply disable bloom intensity post process when it is at at zero. That keeps the other effects active.