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Lightmass Errors

Hello All,

At the moment my lightmass is acting strange, i wonder if anyone may be able to help me out. I have around 20 objects in my scene, including walls and everything, each is set to 1024x1024 for lightmass rendering. At the moment, if i hit production render or preview render, the lightmass is happy to start, then hangs on 0% for a bit before killing the process. As far as i can tell, i don't get any errors in the message log, it looks like it just stops, and i've rendered far bigger scenes with far more objects before on the same computer. I have 64gb ram, and im using windows 10 if it helps, but at the moment it seems like it may be a memory limit issue?

I should also add the process SOMETIMES works, but it seems very unpredictable as to when. I'd say it fails around 70% of the time at the moment.

Id appreciate any help

Product Version: UE 4.12
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asked Aug 03 '16 at 05:25 PM in Rendering

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Hi Dark_Jubei,

Check out the following link:

Why is my light build stuck at X%, or Why does building lighting take so long?

To show the Swarm Agent while building lighting in UE4, click the Swarm icon in the lower right of your Task bar in Windows:


Make sure you are using a Lightmass Importance Volume to make sure you are not rendering unneeded space.

A Couple of other steps to try:

  1. Delete the Config, Intermediate and Saved files in case a file has become corrupt

  2. Try steps listed in the Link above

  3. Test Build Lighting in a Blank Third Person Project to see if lighting is stuck there.

  4. (Last Resort) Migrate your assets of your current projects to a blank project where light is working

-Let me know if none these steps help,

Steve H.

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answered Aug 04 '16 at 07:46 PM

avatar image Steve Hardister ♦♦ STAFF Aug 08 '16 at 02:53 PM

I'm marking this as accepted for tracking purposes. If you are still experiencing Lightmass Errors, please respond with what steps you've tried from those listed above. -Thanks.

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