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Lighting Build Taking Long Time (4.7.3)

I created a Third Person Project and after it loaded I clicked the build button. The Lightmass swarm starts up as it normally does but it is taking a little over two minutes to complete the build. This is a drastic change from 4.6. In 4.6 the build takes about 10 seconds. I even tried creating a new project thinking something was wrong with the one I made and got the same result. Below is what the build looks like. Does anyone know if something changed to cause this long build time?

Thanks, Brent

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asked Mar 19 '15 at 06:15 PM in Rendering

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3 answers: sort voted first

Hey Zuppers,

I've not noticed this kind of drop on my end. Would you mind sharing your DxDiag along with the swarm agent log from 4.6 in comparison with 4.7?

If we have a machine here with similar specs I can possibly compare and see if there is a significant difference. On my machine here (which is pretty top end) and my machine at home (Mid-range at best) I've not noticed this behavior.

Let me know.

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answered Mar 20 '15 at 09:38 PM

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Tim Hobson ♦♦ STAFF
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avatar image zuppers Mar 22 '15 at 05:26 AM

Sorry for the delay. I've attached my DxDiag info as well as the logs for 4.6 and 4.7 swarm agent. Let me know what you find. I should note that I'm currently running the swarm on my local machine and I do not have a coordinator setup. I will run multiple machines in the future when lighting builds begin to take longer.


UE4.7.3 Swarm Log

UE4.6.1 Swarm Log



[1]: /storage/temp/35299-dxdiag.txt

avatar image master_rigel Apr 01 '15 at 05:01 AM

I am encountering the similar behavior on 4.7.3 using the first person template, however the engine is not recording errors here. I'm just getting an unreasonable amount of time to build the scene. 2-3 minutes.

My machine is Windows 7 Home Premium 64 BIT 16 GB RAM

AMD FX(tm)-4300 Quad Core Processor at 3.80 GHZ

NVIDA GeForce GTX 750

avatar image master_rigel Apr 01 '15 at 08:52 PM

what fixed this problem for me was over-ridding the lightmap resolution for all static mesh actors in the scene.

Changing the lightmass ratio seemed to have no affect on the end result.

I discovered that the floor has a lightmap resolution of 2048, and the walls have lightmap resolution of 1024. This my have something to do with the slowdown.

avatar image Stockbrot Sep 26 '15 at 11:04 AM

I am still having this issue, everything in my scene is 2d and made out of a sprite. if I set my view mode to "Show Lightmapdensity" everything is a dark green (low density). I am using a lightmass importance volume, but nothing works. it just goes to 75% and stays there for infinity

avatar image zuppers Sep 26 '15 at 10:32 PM

Stockbrot, I'm sorry I don't think I will be much help on this one anymore. I've since upgraded to UE4.9.1 and I haven't had any major issues with lightning yet. This also sounds like it may potentially be a slightly different problem. I've never had lightmass hang and not finish. Lightmass would just take a long time, usually around two minutes, instead of the five seconds it takes now.

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I can confirm this bug.

Reproduction: start a new project, use template ThirdPerson Blueprint, hit 'Build Lightning Only'.

Issues: building of lighting takes more than 3 minutes instead of 1-2 seconds; lightmap has a wrong density.
Lighting Density
*Bad swarm log.

Issues start here:
BAD LOG: 10:24:09 PM: Caching Irradiance Photons complete, 1.994 million cache samples in 2.7 seconds
GOOD LOG: 10:33:10 PM: Caching Irradiance Photons complete, 0.013 million cache samples in 0.0 seconds

Workaround: set LightingInfo->LightMap Resolution Ajustment -> Ratio to about 10, build Lighting, then reset Ratio to 100 (or more).

Best, Andrew.

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answered Mar 24 '15 at 12:22 AM

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avatar image zuppers Mar 25 '15 at 09:46 PM

Thank you for the work around! I had to check Static Meshes and BSP Surfaces under Primitive Types in order for this to work for me. But after that was done, adjusting the ratio to 10 and then back again did the trick.

alt text

Thanks, Brent

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Okay. I have a partial answer. I can share the difference between 4.61 and 4.73.

Third Person blueprint for 4.61 uses all bsp brushes as far as I can tell. The lightmap resolution doesn't exceed 16 for those brushes.

In 4.73. The lightmpa resolution for the walls and floor are 1024 and 2048 respectively. Plus the walls and floors are all static meshes.

Looks like Epic either needs to do some more work on optimizing lightmass for static mesh actors, in order to improve the shadows, or it's a good idea to keep BSP brushes in your toolbelt for the time being.

Cheers, Rigel

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answered Apr 02 '15 at 04:45 AM

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avatar image zuppers Apr 02 '15 at 05:21 PM

Thanks for the reply! I can't believe I didn't realize they changed from BSP to static mesh's. I can confirm that just changing the static mesh resolution does work. Adding new static meshes to the level does not produce any problems so I think I'm good to go here.

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