Lightmass: multi-bounced sky lighting

SwarmAgent always distributes the UnrealLightmass.exe on the master to others.

This is seriously awesome. I’ve had so much trouble with indirect lighting in lightmass that I have almost given up, I’ll give this a run on my scenes :smiley:

Incredible work man! The lighting travels so beautifully, it looks like Pixar’s renderman! :wink:

I did some tests from the current scene that I have been working on. The setup was Directional + Skylight.
The rendering time was about 3x times faster with a better samples deifinition.
I have noticed some bugs coming from the directional lighting.

I will do more tests when I get some time!

This is amazing, to be clear, you got that performance improvement without doing any setting changes between the two versions? How many bounces were you using?

EDIT: Removed images from quote

Thanks! Waiting for more results from you to identify bugs more clearly.

I think that is because the scene’s contrast in lighting is reduced by multiple bounces, then we need fewer adaptive refinement levels to achieve a good result.

@rafareis123 @Norman3D

Bad news: I found a bug that causes all lights to lose their first bounce (second and later on are preserved) :frowning: The 4.15 binary is updated, please redownload it and try again.

Hi, awesome results with this!

Any help on how to implement this? I did a quick search and couln’t find out where or how should I use the file.]


Replace UE_4.15\Engine\Binaries\Win64\UnrealLightmass.exe with the provided one.

The lost first bounce is now fixed.

Before fix:

After fix:

With a directional light:

Even better! Is the issue you linked to before with the spotlight also fixed? Or is this something you can’t properly fix on your side? Would you advise to avoid using spotlights if possible for our bakes?

I did a quick fix (disabled indirect path driven photon emission), you can have a try, can potentially increase build time:

thanks! i’ll post some images later!

A few tests with a more complex scene. It’s 25-30% faster without lose quality on samples (3 hours vs 2 hours - Too many samples in this one :slight_smile: The contact shadows in small pieces are better also. but I’m not so sure about the lighting value falloff, maybe is it too exponential? I don’t know.

I will test the latest update with the directional lighting and post more results.

@Norman3d : I used 20 bounces


Thanks for those tests! Are them done with the updated one, or the very first version? When comparing the second picture to orignal lightmass’s and iray’s, it seems that the first bounce of skylight is lost.

Edit: Is the skylight’s lower hemisphere set to black in engine?

I did with the first version, I haven’t tested the update yet. Yes, a solid black color (in the original lightmass and yours)

Oh, so is that the reason why the ceiling in iray is much brighter than lightmass? :confused: Is the lower hemisphere in iray also black?

Yes. I used the same HDRI in all renderings. The ceiling brightness from the original lightmass is similar to iray. I will create a more precisely test about it. Let´s see!

Wow ! This is really really really cool ! Congrats dude !

Very impressive light filling and color bouncing improvement. But honestly, I’m not sure what you changed in lightmass binary. Original skylight had only 1 bounce?

Hey Luoshuang !

That’s some seriously cool stuff there, having more than one bounce on skylights really gives more depth to baked lighting.

I tried to reproduce your lightbleed scene but I can’t quite get similar results with my setup…

This is one of the results I got with a skylight intensity of 3, level scale of 0.1, 5 bounces, indirect quality of 8 and indirect smoothness at 0.75. I am also building lights at medium quality level to decrease bake durations a lot.
I can’t quite find the right setup to have as defined shadows and vibrant colors like in your shots.

What are your lightmass/skylight settings ?

Antoine aka LegendreVR