4.9 Preview 4 Build Lighting getting stuck

After creating a new project in the 4.9 Preview, and it working fine for a while, I tried rebuilding the lighting because I had changed a few properties of lights and gotten rid of a couple, with my scene now only containing dynamic lights, and lighting building no longer works - It gets stuck at around 50 - 60% and never completes.

With fully dynamic lighting you dont need to build the lights anyway. If it is still bothering you create a new project, setup a simple level with static lighting and build the lights(dont forget lightmass importance volume) and see how it goes.

Even so, it doesn’t change the fact that it is a bug

Hello Oscar,

From what you have described you are saying that your project did work for a while. Then, whenever you changed a few properties within your lights your lighting build fails.

I have a few questions for you that you can try in order to troubleshoot this issue,

1.) Can you recreate this in another project?
2.) If you change the settings back does the lighting build then complete?
3.) Have you tried to Force No computed lighting found in the World Settings?
4.) Have you clicked off Allow Static Lighting inside of your Project Settings?

Please let me know if any of these troubleshoots are viable and if they fix your issue.

If they don’t then please link me your .uproject, content, and config folders along with your DxDiag. I will then try and recreate your issue in a controlled test environment.

Thank you,

Hello Oscar,

I haven’t heard from you yet. I was wondering if you were still experiencing this issue? Also have you had a chance to test the above mentioned steps?

Thank you,

Hello Oscar,

For tracking purposes I will be marking this thread as closed. If you are still having this problem then please feel free to post again. I will reopen this issue at that time.

Thank you,

Hi,

I’m having the same problem.

My project comes from the 4.8 and this morning I update the engine and the build light get stuked.

Answering to 's questions, with Force No computed lighting ticked the lights compile but loosing the ambient light shadows.

And I have clicked on and off the Allow Static Lighting option, but not solve the problem.

With a new fresh project the lights build right.

Ok, I succeeded in building lights. I was not searching this but I found it.

I just place a Post Process Volume in the scene, and the lights build like a charm.
I dont remember if the scene I had before the 4.9 has one PP Volume by default. The scene was created from a default blueprint blank project.

Maybe in the automatic conversion from 4.8 to 4.9 something get lost.

Again, the build lights process fail.
Now I can’t fix it in any way.
The weirdest thing is that the swarm agent says that lights are at 100% but the editor don’t finish the process, pic attached

Hello erkyle,

I am sorry you are still having this issue. There have been a number of issues reported for lighting builds when copying from 4.8 to 4.9. The best that we can tell is that information is being carried from 4.8 to 4.9 that shouldn’t.

“Before you try this troubleshoot, please make a copy of your 4.9 project as to have a clean backup.”

1.) Delete your Intermediate, Saved, and Derived Data Cache directories from your project. This effectively forces the engine to rebuild non code related content associated with the engine.

This does not delete your assets or your textures. This is a hard reboot for the engine and forces it to delete residual information left from 4.8 and rebuild it inside of a new project.

Please let me know if this fixes the issue.

Thank you,

Thanks a lot , that fix the problem.
I lost my test map, but sure I delete something wrong and the map don’t have important elements, so everything it’s ok.

Thank you, cheers.

I tried this fix (though my project did not have a Derived Data Cache folder), and I am still unable to build lighting; it gets stuck at either 75 or 80%.

My project came up from 4.7, and I converted it in-place in 4.9.1. Any way to work around this? I don’t want to have to go down to 4.8.3; but I may have to…
(my project is in source control, so I can roll it back to before the in-place conversion).

Hey Jonathan,

We recommend that you do not convert in place, but make a copy when converting from older versions of the engine.

I suspect that could be what’s causing the lighting to hang at 75% or 80%. If not, can you reproduce this in a fresh project in 4.9.1?

If you could answer these couple of questions and link me your DxDiag then I can continue to look into what is causing this.

This is all Unreal Engine 4.91

Okay. I have a solution here. Not sure why, but this stuckness appears to be dependant on something in the BSP brushes. Perhaps the light build is assuming that certain actors are present prior to attempting to build. Perhaps the light build was not tested on an empty map prior to shipping the product. In any case adding any BSP brush will solve the issue immediately.If you remove the bsp brush, then light build will fail all over again. Also, if the bsp brush is not placed directly at 0,0,0 the fix won’t work properly. If set the bsp brush at x-200 the lighting will fail at 92%. if I place the bsp brush at x-400 the lighting will work again instantly. If i add a static mesh box from the basics and set its scale to x2 then the lighting will build instantly the same way it will with a bsp box brush at 200px. This behavior is so bizarre.

This is happening for me in 4.9.2 - lighting build stays stuck at 75%.

If I delete my LightmassImportanceVolume, the lighting rebuild completes no problem. If I re-add a new one, the problem comes back.

If I create a BLANK PROJECT in 4.9.2, make a new empty level and just drag a LightmassImportanceVolume into the empty level and rebuild, it just gets stuck at 50% and never finishes.

So for now I’m just not using a LightmassImportanceVolume.

There is nothing suspicious in the log. Here is my DXDiag.

Hey guys,

This is a known issue and is currently being addressed by our development team. Thank you very much for reporting this issue.