Hello,
Is anyone else experiencing weird emissive lighting when it comes to gpu lightmass-built lights from emissive materials? Latest drivers, none of the GPULM settings affect it, and the meshes all have proper lightmap UVs.
5.1.1 :
5.2 :
It can’t be seen in the screenshot but the light is in fact being built, just not around the mesh, but in a larger radius and with reduced strength compared to 5.1.1. I can’t find any GPULM changes in the 5.2 release notes, any thoughts?
After hours of searching for a fix, I’ve found that adjusting the base color of the material finally gives me at least some light. Maybe GPULM is using base color instead of emissive color? It’s very dim, base color is auto clamped 0-1. Without base color connected, there is no bounce light from emissive light.
Same issue here! The base color doesn’t really solve the issue fully. Is there a bug report submitted for this that we can track?
I didn’t bother submitting a bug report, but the issue seems to be fixed in 5.3 preview 1, even though other things are now broken… we’re staying on 5.1 for now.
It’s actually not fixed in 5.3 either! I did a proper, structured test with the exact same level from the Archvis starter content in each version and only 5.1.1. gets emissivive lights baked.
Chiming in here… Yes, emissive light sources with GPU light builds are broken since 5.2 and are still broken in 5.3 (final release).
This bug keeps us from importing 5.1 built maps to the newer engine. We noticed the bug already in 5.2 and hoped that it would be fixed in 5.3. Turns out, it’s still broken. Frustrating…
Same issue there too, I’d hoped that would be fixed with 5.3, but no…
Very frustrating! I’ve already submitted a proper bug report (haven’t heard or seen anything yet) and I encourage everyone affected by this to do the same. That’s the only way we’ll get Epic to take notice of this. Very strange that this glaring bug hasn’t been addressed yet.
Hey @HTPlatypus 
I have gone ahead and submitted a bug report for the issue you have described above. After it has gone through our approval process, you’ll be able to track the issue here:
@Johan.Folke Do you have the link for your bug report that you submitted? I want to make sure we have your bug report and this one linked together.
I don’t have a link, since the bug doesn’t seem to have been registered from my report yet. I do have the case number, if that helps? Case # 00610693, Submitted Aug 15.
Yes, that’s perfect! Thank you
Oh, I am glad I found this.
I have spent a few hours trying to figure out why our emissive materials were not working with GPU Lightmass in 5.3 and now I know.
This is a rotten pain, we need emissive lighting for the mobile app we are developing, how can something like this get through QA is beyond me. I literally left Unity after our last project because of issues that are simply too painful to keep working around… and what do you know… something like this bites us in Unreal.
Totally demoralizing!
Just wondering if there is any update on this and whether it is due to be fixed in 5.3.1?
Since moving our VR project from Unity this is the one piece that is holding us up, i.e. not being able to have emmissive materials contribute to the baked lighting.
Kinda stuck between a rock and a hard place at the moment 
Everybody who faces this issue, make sure you upvote its importance in the bugtracker:
I voted!
It says 5.4 targeted fix, that is terrible news, I guess they don’t care about those that use baked lighting now Lumen has come along 
It does also say to mention the issue logement in the thread too, so here it is: UE-195177
The bug report says “Emissive material lighting falloff regression in GPU Lightmass”
I don’t get ANY lighting from emissive material when baked, doesn’t matter how intense I make the material (this is in 5.3.0)
@JW3153 I apologize, I wish I had better news! Please stay patient, we’re working as hard as we can
Yes, the target fix is currently set for 5.4; implementing a fix to submit earlier wouldn’t be possible because we want to make sure when a fix is implemented, it is done properly and our users (such as yourself) don’t run into any other issues caused by the fix. Thanks for understanding!
This is super disappointing, especially since this bug has been reported several times since 5.2 was released. It essentially forces anyone using GPU Lightmass to stay at 5.1 until 5.4 is released (whenever that might be). How this got through even basic QC is mind boggling. I noticed the issue 5 minutes after installing 5.2.
Since it’s a plug-in, couldn’t Epic just post versions compiled for 5.2 and 5.3 here, even if it’s “unofficial”?
The wording on the bug report is a bit worrying. It should say “Emissive lighting with GPU Lightmass completely broken in 5.2/5.3” to accurately reflect the severity of the bug.
I agree. The current wording makes it sounds as if it’s still somewhat working, while it’s in fact 100% broken. It is, as if emissive light sources were removed from GPU lightmass entirely.
Right now, no one who uses GPU baking and who ever placed a single emissive light in his map, can upgrade to 5.2 or 5.3. Doing a CPU bake is also not an option, as it (again) looks different.
This critically affects thousands of people. Many of them may cluelessly search the web, why their maps don’t look like they used to, before the “upgrade”. May luck lead them to this thread and to the bug report, so they can upvote the fix.
EDIT: To be fair, the GPU lightmass plugin states that it’s still in “beta”. So, from a professional standpoint, I can understand why it may not be a critical priority to Epic. Unfortunately.
It’s been in beta for years now, so at this point it’s more like Epic forgot to remove the “Beta” tag than anything else.
