# How do I compile lightmass? **URL:** \ **Category:** Programming & Scripting\ **Tags:** unreal-engine\ **Created:** [June 26, 2017, 1:13pm UTC](https://forums.unrealengine.com/t/how-do-i-compile-lightmass/396596 "2017-06-26T13:13:53Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![anonymous\_user\_19cc2883](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_19cc2883](https://forums.unrealengine.com/u/anonymous_user_19cc2883)\ **Post date:** [June 26, 2017, 1:13pm UTC](https://forums.unrealengine.com/t/how-do-i-compile-lightmass/396596/1 "2017-06-26T13:13:53Z")
Everytime I press Build in my Unreal engine editor an error pops up wich say : Lighting build failed. Swarm failed to kick off. Compile Lightmass. Now I dont have any clue how I can compile the lightmass. Can you help me? ---
**Author:** ![Nachtmahr](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Nachtmahr](https://forums.unrealengine.com/u/Nachtmahr)\ **Post date:** [June 26, 2017, 2:36pm UTC](https://forums.unrealengine.com/t/how-do-i-compile-lightmass/396596/2 "2017-06-26T14:36:37Z")
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**Author:** ![Daciansolgen](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Daciansolgen](https://forums.unrealengine.com/u/Daciansolgen)\ **Post date:** [May 19, 2018, 10:33pm UTC](https://forums.unrealengine.com/t/how-do-i-compile-lightmass/396596/3 "2018-05-19T22:33:14Z")
i have same problem ☹ nothing works. ---
**Author:** ![yoko3d](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/yoko3d/32/592042_2.png) [@yoko3d](https://forums.unrealengine.com/u/yoko3d)\ **Post date:** [October 24, 2018, 10:30pm UTC](https://forums.unrealengine.com/t/how-do-i-compile-lightmass/396596/4 "2018-10-24T22:30:38Z")
This thread worked for me. [https://forums.unrealengine.com/development-discussion/rendering/121445-how-to-compile-lightmass](https://forums.unrealengine.com/development-discussion/rendering/121445-how-to-compile-lightmass) Hope this helps ---
**Author:** ![anonymous\_user\_0ceb96a8](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_0ceb96a8](https://forums.unrealengine.com/u/anonymous_user_0ceb96a8)\ **Post date:** [April 22, 2019, 7:20pm UTC](https://forums.unrealengine.com/t/how-do-i-compile-lightmass/396596/5 "2019-04-22T19:20:20Z")
If anyone still needs this… I was building UE 4.22 from source in Visual Studio and got this problem. This answer probably doesn’t pertain to the launcher version of UE. PLEASE NOTE: I have no clue whether what I did was a good idea–just that it solved this problem at the time. The solution was to build the UnrealLightmass project in Visual Studio. To do that, I couldn’t just right click UnrealLightmass and build. (I got an invalid configuration for Win32 message.) First, r-click UnrealLightmass \> Properties. Click upper right button to go to the Configuration Manager. (Or just get to Configuration Manager any way you like). In the list, find UnrealLightmass. Change the configuration from ‘Invalid’ to ‘Development\_Program’ (random guess) and Platform x64. Then, r-click UnrealLightmass and builld. Relaunch the engine for good measure. This allowed the Swarm Agent to work in the Editor. But, again, I have no idea if my build configuration makes any sense. ---
**Author:** ![anonymous\_user\_b81eb449](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_b81eb449](https://forums.unrealengine.com/u/anonymous_user_b81eb449)\ **Post date:** [May 17, 2019, 6:04pm UTC](https://forums.unrealengine.com/t/how-do-i-compile-lightmass/396596/6 "2019-05-17T18:04:53Z")
Thanks. That worked for me too in 4.22 ---
**Author:** ![exitlights2](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@exitlights2](https://forums.unrealengine.com/u/exitlights2)\ **Post date:** [May 18, 2021, 2:24am UTC](https://forums.unrealengine.com/t/how-do-i-compile-lightmass/396596/7 "2021-05-18T02:24:01Z")
This worked for me in 4.26.1, too. ---
**Author:** ![MrFly79](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@MrFly79](https://forums.unrealengine.com/u/MrFly79)\ **Post date:** [May 23, 2021, 10:31am UTC](https://forums.unrealengine.com/t/how-do-i-compile-lightmass/396596/8 "2021-05-23T10:31:35Z")
Thanks, solved the problem in 4.26.2 anyone knows why this is happening? ---
**Author:** ![NerdHerdGames](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@NerdHerdGames](https://forums.unrealengine.com/u/NerdHerdGames)\ **Post date:** [April 15, 2022, 2:25pm UTC](https://forums.unrealengine.com/t/how-do-i-compile-lightmass/396596/9 "2022-04-15T14:25:41Z")
You are a life saver! That worked for me in 4.26.1 ---
**Author:** ![anonymous\_user\_4da27190](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_4da27190](https://forums.unrealengine.com/u/anonymous_user_4da27190)\ **Post date:** [July 12, 2022, 6:43pm UTC](https://forums.unrealengine.com/t/how-do-i-compile-lightmass/396596/10 "2022-07-12T18:43:22Z")
I found that deleting the intermediate and saved folders (except config’s) solved the issue without re-compiling