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Problems building lighting from command line

I'm having trouble getting a command-line driven lighting build to succeed, even with a very simple map based on the startup template.

There are a couple of errors in the log file, but I'm not sure which one is relevant, especially because some lines seem contradictory (errors are reported, then a summary line says 0 errors).

Here are the lines that include the word "error":

     LogDerivedDataCache:Error: Could not save memory cache M:.
     LoadErrors: New page: Loading map: testmap.umap
     MapCheck: Info Map check complete: 0 Error(s), 1 Warning(s), took 31.881ms to complete.
     LogEditorBuildUtils:Warning: Map errors occurred while building.

Is it maybe that first one, about the memory cache (M: drive is where the project is stored, but I believe I should have all of my asset caches set to a shared network location)? Where do I go to change that?

Any other ideas?

Product Version: UE 4.9
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asked Sep 08 '15 at 07:14 PM in Rendering

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avatar image Logan Bailey ♦♦ STAFF Sep 11 '15 at 03:30 PM

Hello HypotheticalEric,

I am referring you to a post by another user attempting the same thing. I believe we do not officially support building lighting from a command prompt. There was a pull by another user to have this implemented and on this post there is a link to how it has been implemented.


Thank you,


avatar image HypotheticalEric Sep 11 '15 at 03:39 PM

Hi Logan, That's actually the same post where I found the command line parameters I was using to try it out.

Is there anywhere I can log this as a feature request? It would be a pretty critical need for serious arch-vis work since it would allow us to queue up multiple builds to run on the render / build farm without having to manually start each one.

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I can enter a feature request for you. I definitely see the advantages for such a feature.

I have entered a feature request with your uses mentioned in the description.

The ticket number is UE-20999. I will keep you posted on this features progress.

Thank you,


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answered Sep 11 '15 at 03:45 PM

avatar image HypotheticalEric Sep 11 '15 at 03:53 PM

That's great, thanks very much Logan!

  • Eric

avatar image mrenneke Mar 16 '16 at 03:44 PM

Are there any news on the feature request? I am also trying to automate the light build in my current project, but did not have any success so far. That"s when I stumbled upon this thread...

avatar image Lovecraft_K ♦♦ STAFF Mar 16 '16 at 06:47 PM

Hi mrenneke -

While I do not think the implementation will be fully complete as of the launcher version of 4.11, you can test this feature via the Github version as this commit:


Runs a lighting build for specific, or all, map(s). Reusing the ResavePackages commandlet. The commandline for the commandlet is: ProjectName -run=resavepackages -buildlighting -allowcommandletrendering -map=optionalmapname

Script added to UAT to automate the process. The commandline for this is: RebuildLightmaps -project="My:/Absolute/Project/Path.uproject" -MapsToRebuildLightMaps=OptionalMapName

Thank You

Eric Ketchum

avatar image Ironbelly May 05 '16 at 03:02 PM

Link is broken

avatar image Adam Davis STAFF May 09 '16 at 07:03 PM

Hi Ironbelly,

To access that link, you will need to sign into your github account. Once you do so, click the link again and it should lead you to the proper page.

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