Failed to build lighting! - For no reason

[anonymous_user_a9ff031a1 (anonymous_user_a9ff031a)]

Hello,

I’m diving in Unreal Engine with big hopes. I’m doing Udemy course and I’m at EscapeGame stage, which is nothing more than simple room with couple walls form starter content, chair and door with auto open mechanism. At some point my project stopped building lighting and I cannot figure out why. From code side, it’s C++ project only, with 2 classes, one attached to chair one to door with simple code to read position and change tilt.

What I have tried:
-Copy&Paste items from old map to new map
-Recreate map
-Play around with settings by suggestions from different online discussions board including Unreal Engine forum and stackexchange.
-I tried removing objects one by one and even though I removed everything, it still failed.

Here is log:

MapCheck: New page: Map Check
LightingResults: New page: Lighting Build - Jun 4, 2019, 1:33:03 AM
LogStaticLightingSystem: Warning: No importance volume found, so the scene bounding box was used.  You can optimize your scene's quality and lighting build times by adding importance volumes.
LogStaticLightingSystem: Running Lightmass w/ ImmediateImport mode ENABLED
LogStaticLightingSystem: Running Lightmass w/ ImmediateProcess mode ENABLED
LogStaticLightingSystem: Running Lightmass w/ Sorting mode ENABLED
LogStaticLightingSystem: Running Lightmass w/ Mapping paddings ENABLED
LogStaticLightingSystem: Running Lightmass w/ Mapping debug paddings DISABLED
LogEditorBuildUtils: Build time 0:00
LogUObjectHash: Compacting FUObjectHashTables data took   0.99ms
LogUObjectHash: Compacting FUObjectHashTables data took   0.66ms
LogFileHelpers: Editor autosave (incl. sublevels) for '/Game/InitialMap' took 0.020
LogStaticLightingSystem: Warning: Failed to build lighting!!! Lighting build failed.
DumpUnbuiltLightIteractions
Lights with unbuilt interactions: 2
    Light LightSource
    Light PointLight_1
Primitives with unbuilt interactions: 9
    Primitive StaticMeshComponent /Game/InitialMap.InitialMap:PersistentLevel.Wall_400x304.StaticMeshComponent0
    Primitive StaticMeshComponent /Game/InitialMap.InitialMap:PersistentLevel.Wall_400x303.StaticMeshComponent0
    Primitive StaticMeshComponent /Game/InitialMap.InitialMap:PersistentLevel.Wall_400x302.StaticMeshComponent0
    Primitive StaticMeshComponent /Game/InitialMap.InitialMap:PersistentLevel.Wall_400x301.StaticMeshComponent0
    Primitive StaticMeshComponent /Game/InitialMap.InitialMap:PersistentLevel.Wall_400x300_5.StaticMeshComponent0
    Primitive StaticMeshComponent /Game/InitialMap.InitialMap:PersistentLevel.Wall_Door_400x300_2.StaticMeshComponent0
    Primitive StaticMeshComponent /Game/InitialMap.InitialMap:PersistentLevel.SM_DoorFrame_8.StaticMeshComponent0
    Primitive StaticMeshComponent /Game/InitialMap.InitialMap:PersistentLevel.SM_Chair_2.StaticMeshComponent0
    Primitive StaticMeshComponent /Game/InitialMap.InitialMap:PersistentLevel.Floor.StaticMeshComponent0
Cmd: MAP CHECK NOTIFYRESULTS
MapCheck: New page: InitialMap - Jun 4, 2019, 1:35:06 AM
MapCheck: Error: WorldSettings_1 Maps need lighting rebuilt 
MapCheck: Map check complete: 1 Error(s), 0 Warning(s), took 0.77ms to complete.

Help appreciated. Thank you.

[anonymous_user_a9ff031a1 (anonymous_user_a9ff031a)]

It seems that now, none of projects will build lighting. I tried creating default templates and none managed to build lighting with the same error. It’s macOS 10.14.4

[anonymous_user_a9ff031a1 (anonymous_user_a9ff031a)]

I found the root cause of this. It seems it might be affected by any proxy and firewall running on your computer and that includes MacOS Firewall, Little Snitch and/or any VPN. One of VPN I use caused this, the other one works fine. Any workaround and perhaps fix from UT4 team? As internal connectivity isn’t necessarily broken by VPN, it is broken just for UT4.

[anonymous_user_4b9a669b]

@anonymous_user_a9ff031a1

I found the root cause of this. It seems it might be affected by any proxy and firewall running on your computer and that includes MacOS Firewall, Little Snitch and/or any VPN. One of VPN I use caused this, the other one works fine. Any workaround and perhaps fix from UT4 team? As internal connectivity isn’t necessarily broken by VPN, it is broken just for UT4.

Thank you! It works!

[firebait1979]

This was the case for me too. So +2 on this answer

[Pitoui]

incredible. was becoming crazy was indeed my VPN
Many thx

[DeisukeAramaki]

confirmed - VPN was blocking the lighting build on MacOS Big Sur - how is that even possible?

[Arkiras]

Might be something related to how VPNs configure your network settings vs. what Unreal would expect for Swarm? (Swarm Unreal’s distributed lighting build app.)

No idea though, especially since this seems to be a Mac issue and Swarm requires Windows…

[petermeansrock]

@DeisukeAramaki

confirmed - VPN was blocking the lighting build on MacOS Big Sur - how is that even possible?

@Arkiras

Might be something related to how VPNs configure your network settings vs. what Unreal would expect for Swarm? (Swarm Unreal’s distributed lighting build app.)

No idea though, especially since this seems to be a Mac issue and Swarm requires Windows…

As I ran into this issue on macOS and was also unblocked by disabling my VPN, I thought it would be helpful to shine a bit more context into this thread.

On macOS (and I believe Linux as well), Unreal Engine uses the class FSwarmInterfaceLocalImpl to launch a subprocess named UnrealLightmass in order to precompute lightmaps for static and stationary lights. Both the parent UnrealEditor process and the UnrealLightmass subprocess use this same Swarm interface local implementation (not to be confused with the Swarm Agent for Windows) to communicate with one another using UDP multicast messages over group address 230.0.0.1:6666.

This means that networking software like firewalls and VPNs may contribute to a breakdown in communication between these two processes resulting in light build failures.