When running the production build of my archiviz project, the indirect lighting sometimes becomes rainbow colored with no apparent reason. Sometimes the mere act of moving into a room from outside the house triggers it. Moving away from that part of the scene and then coming back later sometimes resets it, but sometimes doesn’t. And sometimes once the rainbow bug appears, it spreads to other parts of the scene as I move around.
Any ideas on what might be causing this?
We initially thought maybe our fire niagara actors were causing the flashing issue, but the issue persists even when that’s removed. Also, this bug doesn’t seem to reproduce across different machines and platforms. When I run it locally on my Windows PC, it works fine and I’ve never had this issue, but when my friend runs it on his mac or when we run it on remote Windows pixel streaming servers using A5000 gpus, it happens again (randomly but with pretty high likelihood if I move around in the scene long enough)
if i would guess… something in your scene is emitting unwanted light and gradually spreads thru the lumen scene and radiance cache. you should check all the things that emit light. the purple doesn’t make alot of sense, but it’s a blend between fire red and blue shades. so is the firey yellow.
so… what is the fire particle color? make sure it does not emit directly into the lumen scene.
Thanks for the reply. The fire was like red and yellow, but we got rid of the fire from the scene in our latest build, but the weird color bug is still there. All the emissive lights in the scene are white.
I guess another piece of potential clue is the reflection in the window, which appears to be solid blocks of green, orange, or purple. It’s as if there’s a few colored box lights shining at the window, even though there are none there.
This is actually quite similar to what I experienced in 5.1 and 5.2, and long story short it’s almost certainly a memory overflow and corruption issue.
When lumen has memory overflow/corruption issues, the cache atlases disintegrate into rainbow-colored bits of light- this is in turn propagated to the lumen scene, which means that the other lumen passes pick up on this data; effectively, one bad cache can propagate to your whole lumen scene until it’s just a mess.
Check your skylight: oftentimes the skylight parameterization would get corrupted, which would launch rainbow sparks and colors all over the place. If any of your surface cache textures are doing the same thing, same deal.
Those blocks of color are the low-res radiance probes that are lighting your translucency; enable high-quality transparent reflections to replace them with per-pixel tracing of the lumen scene, which may be better.
As for how to fix them, I’m really not sure unless you’re working on 5.1 or 5.2; then the only solution I can think of is to upgrade your engine to 5.3 where they’ve fixed the memory issue.
