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?

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,

Hi ,
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.


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,

That’s great, thanks very much !

  • Eric

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…

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

Link is broken

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.