Recommenadble GI solution for outdoor scene

hi there,

i am trying to use unreal as a more traditional 3d package at the moment.
its very liberating to light and compose shots in realtime.

currently working on a video and doing some preliminary tests.
i am working with very simple scenes so light is the most important factor.

at the moment using LPV and because of the isometric perspective and resulting camera distance i had to crank the settings way down for shadow to actually work.
the results are allright but with some issues aswell.

apparently there are a couple of dynamic GI solutions so i am asking should i try a different solution - if yes which one would be best. (considering non gaming purposes)

all this talk about compiling is daunting but i would like to give vxgi a go.
any thoughts would be appreciated.


VXGI gives the best result for dynamic global illumination–performance isn’t good enough for game releases but if you’re doing renderings that won’t matter since even if it takes a full second to render that’s way faster than using baked lighting or rendering in Vray or whatever.
Last I tried, which was for 4.6 I think, it wasn’t quite straightforward to build the VXGI branch, maybe it’s different now and following the instructions will work properly without having to go through the forum thread to find out what thing you need to change for it to compile successfully.

thank you very much for the insight. that is exactly along the lines i had in mind.
just wanted to know before i started mucking about with compiling if it is indeed the best quality option.
i already went through the alot of threads about installing do not feel really comfortable.
any chance of it messing up my system?

The current “official” method is to use Lightmass. Lightmass bakes GI and shadows to precomputed textures. Then on your directional light you can turn on cascaded shadow maps by dragging out the distance, so you get nice, crisp, clean dynamic shadows up front, and baked shadows in the distance. I’m currently editing my own landscape map with lightmass, 2017x2017 (approximately 2 kilometers length and width, 4 km. squared), and it looks awesome! Lightmass also bakes lighting caches for dynamic objects, so dynamic objects will still have appropriate bounce lighting. Combined with ambient occlusion, it’s enough to fool most, and it’s the highest quality result.

There is a dynamic heightfield GI, but I don’t think the main branch has a dynamic GI solution other than LPVs, and that wasn’t Epic’s code. Sorry.

It won’t mess up your system, it’s just a bit daunting if you’re not a programmer and don’t use stuff like Github, It really should be as simple as installing github and downloading the source and then opening the project solution in Visual Studio and hitting build, but back when I tried it there was some component or something that needed to be recompiled in it which wasn’t something I could figure out on my own. For dynamic GI it’s the best solution, easy to use once you’ve got it compiled.

I wish Epic would bring back SVOGI, just so we can see how it tastes. DX 12 might change things and improve game performance. NVIDIA’s solution is basically the same thing.

VXGI was actually inspired by SVOGI, funnily enough.

Anyway, VXGI is really easy to get going now. Just grab the source from github, run the setup.bat without overwriting any of the files when prompted, then build the engine like usual and then build ShaderCompileWorker. Once you do all that, you’re ready to go, it’s almost the same as building the normal UE4 source at this point.

There are a few optimizations you can do as console commands if you really want to get some performance back when using it, like r.VXGI.MapSize = 32 will make the voxels much larger and make it run a lot faster even if it won’t be quite as accurate. There’s more you can do to get it running faster, but generally those options are all in the post process volume.

To enable VXGI to begin with, you need to pick a light (any type will do) and enable VXGI on the light, then enable VXGI diffuse (and specular if you want realtime non-screenspace reflections) in the post process settings.

much appreciate all of the answers.

i just downloaded the github and the branch from the link:

partly confused by the multitude of links, like the galaxyman version.
i will proceed with the link above.

should i throw the downloaded folder into the root of the 4.10 build and run setup.bat from there?
probably too late til someone sees this - will report back anyway.

thanks guys.

thanks once more to all, seems i got it running.
had to install visualstudio 2013 as 2015 gave out an error.

i will definitely have questions on finetuning so if anyone mind sticking around i would be very grateful.

the cornell box project already has me confused. no idea why there are lights setup behind the green and red cards.
looks like something i would setup for faked bouncing.
also none of the lights seem to react to changing of any of the params except the intensity and hiding them in the world outliner does nothing.

the sci fi hallway on the other hand scene works beautifully.
i love it.

The cornell box project has examples with other types of lighting to compare to VXGI, so just ignore that stuff

got it, thanks.

i am about to start translating my scenes into the vxgi version.

any suggestions what the best way should be?
can i just open the files from the vanilla UE4.10 or should i copy them into the vxg build version?

it also seems that my emissive light materials do not bounce light. (vxgi voxelisation in the material set to on).

You can open normal levels or content of UE4 directly in VXGI and it will be converted automatically.
Since you’re new though, I’d kinda recommend making a duplicate of your content and experiment on that first.
Emissive materials only start working properly in VXGI once you’ve toggled the ‘Omni directional’ flag in the material VXGI properties.

thanks chesire,

yeah i got the prompt straight away to duplicate the project which i did.
i wondered if the projects would display in the launcher but they actually do - with the label “other”. great.

i actually had the box ticked as i was testing and it did not appear to change a thing.
here a screencap. its clear that the point light bounces the cards and the object light does not.


Did you enable multi-bounce via console? (r.VXGI.MultiBounceEnable 1)
Then put it on 2.0 in your PPV VXGI Diffuse section.
If you have a pixel blowup, simply put it on zero and then back to 1.

fantastic. that fixed it.
thanks a million.

Can i build the UE with VXGI for MAC ?

How is the performance hit with VXGI? Is it mainly for Nvidia cards?

Any graphic cards will work but Nvidia gtx 9xx+ have an edge due to their hardware specifically made for vxgi!

Performance hit is very high. If you’re going to use VXGI you need to budget around it, and forget about using it on any platform other than high-end PC.

As an alternative you still have Ryan’s AHR (link) but it isn’t as mature as VXGI and is still highly WIP.

Well, there isn’t anything that matters besides high-end PCs (/jk). For real now, VXGI has a few parameters to squeeze out some performance. On my 970 it runs at 60fps in most scenes, but you should be careful with it.