Why am I getting crazy, random bloom/lighting issues?

We have no idea what is causing the random bloom in the video linked below. The issue is intermittent (sometimes it doesn’t show up at all) and varies in severity, seemingly at random, so we haven’t had any success tracking down the culprit.

If anyone has had a similar issue or thinks they know the cause, all suggestions are welcome.

Thanks in advance,

Your video of two static screenshots means it’s really hard to work out what the problem is - you’ll need to be more specific.

It seems likely to me from your description that it’s a post process effect like eye adaptation (which often doesn’t work desirably) that may be your issue, so it may be worth disabling some stuff and seeing if it alleviates the issue.

Sorry, I understand there’s nothing less helpful than a complaint full of little detail, but as the problem is seemingly random, it’s hard to be very specific. That said, Ill do my best:

We have an open level where a modular city is spawned using a tool made by a programmer. The entire city is surrounded by a lightmass Importance volume. I also have a post processing volume in the level with the default settings applied. The directional light is turned down to about 3 and close to horizontal. The skybox light settings are turned down to nighttime level, where you can see the stars.

Occasionally, in some random areas of the map, the character gets a red, green, or blue bloom that is very overwhelming around him. Sometimes the building meshes turn random colors, and other times random models get the bloom as well. Sometimes the buildings have straight, emissive lines that almost appear to be placed intentionally, except they’re not.

I hope that is at least a little bit more helpful, and please let me know what other details I can/should provide.

Thanks again,


I don’t suppose it’s reminiscent of the issues in this thread?

I’ve also been having strange issues like this. Some of my enemy pawns just glow bright red, even though they have no emissive materials. They do have emissive projectiles that are red and spawn right on top of them, but the projectiles themselves aren’t nearly that bright. Not only that, but I have the visibility turned off on my projectiles right now and it still shows up. I’m not sure what’s causing it.

Thanks Ambershee, it seems to be pretty much the same exact issue. Unfortunately there doesn’t seem to be a solution yet, but I’ll keep trying to figure it out.

This might help to find a problem:

In addition KP, DanielW posted a possible solution on the other answerhub question which also might help you out with this issue:

“Does the artifact go away when you set the ‘r.Cache.LightingCacheDimension’ console variable to 128? There’s a bug with many (>1728) movable components right now that will cause this. Instanced foliage currently does not support lightmaps correctly which are used when the components have static mobility, so both routes are a bit broken.”

Eric Ketchum

Thanks Eric, I probably should’ve mentioned that I’ve been looking there now for answers, but I forgot, so thanks for looking out.

From DanielW again, "Yeah sorry I forgot that’s one of the console variables that can’t be changed at runtime, and console variables you enter in the console don’t get saved. You can add it to Engine/Config/consolevariables.ini for a quick test.

We certainly want to fix it, I’m just not sure when we will get a chance. Hopefully in 4.4."