Lightmass: multi-bounced sky lighting

You should not install this Lightmass.exe for 4.18. These improvements were already added to the engine in 4.18.


Can anyone tell me why I get those jitters shadows ?

4.17 + multi bounce skylight

Here are the lightMass setting + skylight setting .


Where is 4.17 version of this lightmass? i don’t see it in this thread.

The link is in post #189 on Page 13

Thank you for your hard work!

Out of curiosity. I am recently experiencing this issue when I try to build lighting from your testing level

Swarm log:
11:16:49 AM: Processing…
11:16:49 AM: Couldn’t gather the requested number of indirect photon paths! 0 gathered
11:16:49 AM: EmitDirectPhotons complete, 0.000 million photons emitted in 0.1 seconds
11:16:49 AM: EmitIndirectPhotons complete, 0.000 million photons emitted in 0.1 seconds
11:16:49 AM: Marking Irradiance Photons complete, 0.000 million photons marked in 0.1 seconds

Im new to this and still trying to figure out how to post a image.

This indirect photon path issue also makes the final rendering looks wired with incorrect light bounces.I wonder if anyone else is having this issue as well or is it just me.

I think you had exactly my problem. Take a look at your UV Channel 1 (Lightmap) for that mesh. You should see your uv island turned at 45/30 degrees. Try to rotate it to 90 in your uv editor.

How I install this?

Use 4.18 preview and you do not need to install this.

or replace the Engine/Binaries/Win64/UnrealLightmass.exe file in your engine with the correct version linked in this thread.

I don’t know if this has been mentioned (I have quickly looked through this thread and haven’t seen it mentioned), but indirect lighting from emissive materials seems to be broken in 4.18p4.
I’d be a happy camper (even happier) if this could be fixed for release, now that the rest of Lightmass is shaping up so amazingly =)

Did you submit a bug report to Answer hub?

Did a test here in latest 4.18 and indirect lighting from emissive is working correctly.

By default you only get one bounce, same as skylight.

You have to set ‘Num Sky Lighting Bounces’ higher to get more.

Glad I found this thread! Such good information here. Thanks everybody for sharing your settings. Keep up the good work guys!

thanks Daniel
you helped us with embree and portals in 4.11
and its second big jump in ue4 with multi bounced sky lighting

your team ] work was awsome

Oh right, didn’t realise this was counted as a part of the skylight, which I in my test scene had set only one bounce for baking. Thanks, I’ll try it again now =D

I had some time to test the build times on 4.17 and 4.18 and from what I’ve seen, 4.18 is a lot slower than 4.17, using the same settings. I have left the **Num Sky Lighting Bounces **to 1, just as the 4.17 version is natively set up, but the bake times have tripled, sometimes it’s even worse.

I will post the entire scene, lightmass.ini and the settings I’m using in this thread, tomorrow.
I need someone to confirm this, or maybe correct me, if I’m doing something wrong.

I did extensive profiling on all the 4.18 Lightmass changes and my findings were ~5% faster builds in 4.18 with out of the box settings. If you get a chance to confirm the regression, post the repro in an answerhub and send me the link.

OK, I will make a thread tommorow in answerhub and send you the link. Maybe the problem is that I also change the baselightmass.ini.

I had chance to test it again today. I deleted and converted in place the project from 4.17 to 4.18. This time, everything worked fine. Just as you said UE 4.18 was about 5% faster than 4.17.

I guess that there was some bug, when I switched to 4.18 yesterday.

Hey guys. Do u have problems with importing some HDRI images to UE4 ?

DanielW - could u check this as a developer ?

I tested the .hdr import and I found no issues with it. Also there is another way to make use of a HDRI image, if your purpose is to use it as a environment sky. Check this tutorial:

Also don’t forget to set the skylight to SLS Captured Scene and make the Sky Distance Threshold to be slightly lower than the distance where your sky sphere starts.