Dynamic GI : Getting the Most out of LPV ( Light Propagation Volume )

[Frozenfire]

@Teapot Creation;666083

Hi Frozenfire,

thanks for your tips, they will be usefull… as soon as I get LPV to work in 4.15.
Did you already tried on 4.15 ? I’ve got the same result with and without LPV activated, and/but can’t add r.LightPropagationVolume = 1 in the .ini file without making the editor crash and unable to launch the project again.

No I haven’t tried it on 4.15. If this is a reproducible bug you should report it on answerhub

[Daedalus51]

Hey,

good guide to begin with! I think you could document some of the technical backgrounds and limitations of this technique as well so people new to this can better evaluate if its beneficial to their project or not.

Personally, I have very mixed feelings about LPVs and there are many cases where this technique falls apart. However, its good to see people still figuring out how to work with it in a nice way!

Whats your take on interiors and things that are not on the grid though? Maybe you dont encounter many issues like that in your game, but when we worked on Dead Island 2 back at my old company, we really struggled hard to get things to work that are not perfectly aligned to the grid of the world AND the LPV itself.
Also, you might have seen that you can tweak the injection bias for the LPV on a per object base as well! Increasing the global value too much gets rid of a lot of nice bounce lighting, so my personal recommendation would be to adjust the injection bias for thin meshes seperately
(the injection bias basically is the threshold for when an object becomes thick enough to block the light. If you have walls that are thinner than one cell of the LPV it starts bleeding through and the injection bias basically artificially makes that wall thicker so the cell of the LPV doesnt bleed though anymore)

Cheers!

[Frozenfire]

@Teapot Creation;666083

Hi Frozenfire,

thanks for your tips, they will be usefull… as soon as I get LPV to work in 4.15.
Did you already tried on 4.15 ? I’ve got the same result with and without LPV activated, and/but can’t add r.LightPropagationVolume = 1 in the .ini file without making the editor crash and unable to launch the project again.

I think there’s a bug with this, it’s already fixed I believe.

[cadviz]

Hi @Frozenfire
Thank you for sharing this guide and tell how to deal with LPV as a Dynamic GI solution…

Your cool nice rendered screenshots encouraged me to try using LPV in my recent ArchViz project.
And while I’m watching them in focus, I think these decent render results were not only due to your LPV settings,

I may guess there were some other tips & remarks you forgot to tell (may be some other elements OR settings) had been used to improve the render result…!! I don’t know, may be

So; before I get started, I hope (if my guess was true) you share us your other scene settings such as
Directional light setings, skylight settings, and may be you had a BP_Sky_Sphere, SM_SkySphere, or a fog… etc and anything you may find it helpful…

Respecting your statement

@Frozenfire;635920

LPV is a dynamic GI solution. It deals mainly with GI only. Because we don’t have

lightmass/lightmap in Dynamic lighting , what we have is mostly AO ( either from SSAO or DFAO )…

Does this mean I may be able to Export my meshes directly to UE4 without thinking about unwrapping them inside 3DsMax, as you may know **unwrapping **is to create a lightmap texture in channel 2 when using lightmas inside UE4 for baking Lightmaps…!!?

Best Regards

[cadviz]

@mittense;641290

Yeah, so, LPVs are great. They are wonderful. I love them. But they’re also only really one component of getting GI into a fully-dynamic scene. Distance Field GI (VPL meshes) has gone the way of the dodo. But! Heightfield GI is also fantastic. It does have the brief bake period where it generates color values to approximate the terrain, but other than that there’s no baking involved, and you get some good results from it for not too hefty a render thread price.

But, yeah, LPVs + Heightfield GI + Dynamic Skylight + Dynamic atmospheric directional light. ALL OF THOSE THINGS KIND OF APPROXIMATE A REAL-TIME GI SOLUTION.

(But it’s all pretty manageable for any game targeting a year out).

That’s what I’m using here:

[IMAGE]

@mittense;642617

Heightfield GI is astounding, but the lighting only gets applied to static objects. Light Propagation Volumes affect all objects except for translucent materials.

Hi @mittense
Can you please lead me where to find a start guide for Heightfield GI, and may be good tutorials…?
Thank you

[mittense]

@cadviz;752706

Hi @mittense
Can you please lead me where to find a start guide for Heightfield GI, and may be good tutorials…?
Thank you

http://timhobsonue4.snappages.com/distance-field-global-illumination

Though, do note: I’ve had tremendous issues with heightfield GI in a dynamic time-of-day scene (the heightfield GI totally blew out the darkness).

[Frozenfire]

FYI , Heightfield GI is only relevant for Landscape
@cadviz , I don’t believe I’m doing anything particular with my light settings, in fact I even turn down the shadow cascade amount a little to get a little performance.
But there are better people who can answer you on how to get most from dynamic directional light , skylight and others.

[Haoris]

Looks like occlusion is broken.
Intensity, size, fade range, affect the scene but only the light emission is working. Playing with other settings and settings like zero or 1000000000000 doens’t make any change, not even subtle

[Slavq]

Yes, the emissive materials also don’t contribute to LPV anymore. Tested on 4.21.
Is there a way to fix it somehow?

[Alessiana]

Also I can’t make it work with the “Extended luminance” option in the project settings checked and a high value for the direction light like 70k.
Anyone with this problem?

[The_Distiller]

Specular contribution seems to be broken as well.

[anonymous_user_2e33f205]

I have it working. You have to disable *dbuffer decals. Or it will crash. *

[Slavq]

Just to let you know, there is a new SSGI solution in 4.23 and it should be officially announced in 4.24.
I’m curious on how does it compare to the LPV.

[rosegoldslugs]

@Slavq

Just to let you know, there is a new SSGI solution in 4.23 and it should be officially announced in 4.24.
I’m curious on how does it compare to the LPV.

Try it out IMO it’s much more “enable and go” since there are no parameters at the moment. It’s a raycast to the SceneColor, so you automatically get Albedo and Emissive materials contributing with velocity to reduce TAA ghosting. At the moment, it’s pretty expensive even with their default for low ray/sample counts, and it’s screen-space so you get all of those fun issues. But in the situations where it works well, it looks really good.

[5GoldSwordsman]

Hey guys, looking for some dynamic GI solution and was thinking using SSGI but as soon as i enable it, SSAO is dissapearing. Can they not work together or are there any settings/tricks to use them together?

[Vindkald]

They can’t work together. Maybe you could use SSGI with DFAO.

Enjoy