Things To Know About LUMEN [Unreal Engine 5]

hey everyone welcome back so great to see you this is such an exciting time to be alive because with the unreal engine 5 that just dropped lumen is one of the most highly anticipated features one that i've been waiting for ever since ue5 was announced last year so the topic of today's tutorial is going to be all about lumen everything you need to know about it all its project settings how to use it and most importantly all its limitations so with that being said let's get started so just a disclaimer before we get started here because this is an early access version of unreal engine 5 a lot of things are going to change a lot of these new features are pretty much misunderstood at this point you know by pretty much everyone myself included like i'm reading through the nanite documentation and i have no idea what's happening this is such new tech i think it's going to take a while before it becomes the norm so take this tutorial with a ginormous grain of salt my main reason for making the tutorial today is mostly to help you guys with some of the issues that i ran into and how i solved them okay so don't take this tutorial as the holy gospel if some of my tricks here help you out awesome if not that's fine because this is not meant to be a full-fledged you know very well documented very well researched tutorial it's just too early at this point so with that being said now we can get started okay so now that we're unreal the first thing we want to do to make sure that you know lumen is up and running in your scene or in your project is we're going to need to go to the project settings so up up in the top right hand corner here click on settings and open project settings let's get to the boring part first now you'll see on the left hand side here scroll down and there should be a rendering tab right here make sure you click on that and then scroll down until you see global illumination reflections and lumen the current settings right here that i have right now are the recommended setting for ue5 so now the boring parts out of the way let's close this so you can see right here the only thing i have in my scene is a skylight and a directional light so i'm going to go check out my lights here you'll see i have both skylight and directional light if i hide these everything goes dark so if i enable only the directional light you know already we're seeing really nice indirect lighting in here and if i enable the skylight on top of that we're going to get just a little bit more bounce coming from the sky now there's several different ways of controlling the indirect lighting here so the easiest way to get full control over your indirect lighting is to select your main light here so in this case the directional light and in the details panel we're going to search for indirect and you'll see right here we have indirect lighting intensity if i set this to 10 you'll see obviously our gi has blown way out of proportion but you get this just gives you an idea of how you have full control over it so if i want to turn it off entirely i can set it down to zero and you'll see we have no more gi's so i'm going to set it back up to one just so you guys know this is one of the ways you can control it now the next way we can control this with lumen is go into your post process volume select this and once again in the details panel we're going to search for lumen and we have a few other controls here and what's nice is that now you can finally choose which type of gi you want we've got screen space you got ray tracing i'm going to leave it aluminum for now but this is finally where you can control it you don't need to enable it with console commands anymore and that's awesome now lumen also takes care of reflection so not just the indirect lighting but also reflection so what i'm going to do is i'm going to go create a sphere here and drag this up make it a little bit bigger and slap on a chrome material and now you'll see we have reflections on our sphere but you'll notice things are kind of blurry and they pop a little you know depending on how far you are from the from the object now the way i understand it and please correct me if i'm wrong but lumen uses hlods for reflections in this case so obviously i think you're going to get better results with raytrace reflections so you know just kind of you can play around with the settings here now that we i've shown you how to change that in the project settings feel free to experiment a little bit i just kind of want to point you in the right direction and tell you guys about the various settings and why things behave a certain way so again go experiment with the ray tracing reflections as opposed to the lumen reflections but in most use cases i think this is going to be plenty fine unless you have really you really need those clean sharp reflections on shiny objects for example so what i'm about to show you right here is quite possibly the most exciting part of the entire unreal engine 5 revealed this blew my mind during the live stream the other day so i'm just going to go ahead and do it again for all of you who didn't watch the stream i'm going to go ahead and create a sphere here and on the sphere i'm going to slap on an emissive material now notice just by having an emissive material on the sphere the sphere is now a light it's actually casting and emitting not only direct light but indirect lighting as well so if i scale this up way bigger notice how this sphere is illuminating this entire area the fact that this works out of the box this is the coolest thing about lumen in my opinion yes the gi that we get from other tools is great but man i did not expect emissive materials to emit light and not only light but indirect light so i apologize for acting like a five-year-old on christmas this is just really exciting to me so with that being said let's move on to the next point so i think most people understand how lumen works in theory it works pretty darn well out of the box that's pretty straightforward that whole process of indirect lighting is very straightforward once you know how to control it and how to enable in your project but i think where people run into issues with lumen is with things that are kind of unrelated to lumen and one of those things is nanite so i think nana is pretty new tag i don't think many people really understand what it's doing i'm not one of those people who know what it's doing so i'm gonna help troubleshoot some issue that you know i ran into playing around with nanite and lumen and you'll see right here that we have two trees and now one of them looks substantially better than the other so let's pay attention to the right hand tree here and let's zoom in close and now all our shadows are here and our mesh and as soon as we zoom out you'll see the shadows just disappear and then when you get further enough away all the leaves just disappear everything just same thing with the tree archery is just kind of falling apart as we move further away but the other one is fine why is that the only difference between these trees is that the right hand tree right here is nanite and the left hand tree here is just a regular static mesh with no nanite being used so lumen works very well with the static mesh here we've got some nice shadows going on in here some nice highlights happening on the leaves themselves but the nanite tree just looks really bad and obviously i use this as an example because epic has clearly stated that nanite and lumen don't work so well with very thin meshes because everything is kind of mesh distance field based so because of that having thin very thin plane models it's not going to work super well there's a reason why there's little to no foliage in the unreal engine 5 demo so far this is exactly why okay i'm not saying you can't get good results with foliage you can that being said if you're running into issues with your lighting and your models are just not looking very good try making sure that they're not converted to nanite import them with a regular static mesh all right importing as a regular static mesh could be a very simple way of troubleshooting what's causing your issues in your scene now the next issue that i've had and i've seen other people struggle with is the shadows now you'll see that i've placed a wrecked light right next to the table and the chairs here and you'll notice hopefully you can see in the video but these shadows are incredibly noisy they don't look very good and the shadows are a little too sharp for you know considering the size of this light ray trace shadows looked better in 4.26 as opposed to the lumen shadow so how do we fix this and of course in true unreal engine fashion the solution to this is you guessed it a console command i'm really annoyed by this i really wish that you know epic would do away with these solutions that are solved with console commands i just want to have a slider or a check box something in the light instead of having to deal with a million console commands in the project right so the first of which so paying attention to the shadows here now the first console command we're going to use so going at the bottom left-hand corner of the screen here it's great because now the console command is menu is always there and i'm going to type in the following r.shadow.virtual.smrt.raycountlocal i'm going to bump this up to something like 8. and now hopefully you guys can see that the difference there our shadows are suddenly way less noisy okay and then there's another console command that we can enable to help with the softness of these shadows and that is the following smrt.sample parade local eight and then you notice that the shadows got a little bit softer they're still not great like these this just looks really weird we got this kind of just we clearly got some soft shadows happening but we also have this weird hard shadow happening okay so this this seems to be a limitation of lumen i think it's again this little work in progress there's still a lot of unknown so my understanding is that this is somewhat of a limitation of the virtual shadow map that lumen uses and the solution to that is either to back up a little bit more or use a slightly smaller light so notice how if i make this smaller the it does feel a little bit better but again this is not a real solution now i'm not a rendering engineer so i don't actually know what's happening under the hood here i just wanted to show you guys these two console commands which are found in the epic documentation i will include these console commands and a link to the documentation in the description below so go check that out do read the documentation there's a lot to unpack here i just wanted to troubleshoot some issue that i ran into myself so the last issue that we're going to talk about right now and this is something that you may or may not run into this is something issued i ran into this morning and hopefully this helps someone out so we're going to go ahead and create a light up here and create a directional light i'm going to get this light shining in here i like that now you may not be wondering okay i need to increase my indirect lighting right to get some of that sweet sweet bounce happening but you'll notice i'm not getting any bounce whatsoever no bounce at all why is this now the reason i couldn't you know try bumping up my intensity perhaps right and this is more of like a screen space gi this is not the true lumen that we've grown accustomed to seeing in the exterior level and the reason why i'm not getting any proper indirect lighting in my apartment scene here is because of this hdri dome here okay i have a dome texture this is from an evermotion package and so i have a dome out here and it's it's not casting shadows no shadows are cast but even though there's no shadow being cast its effect is blocking the light even though the light is shining in my scene so if i go ahead and i delete this suddenly notice how boom my apartment scene is flooded with light all that gi works now and everything works as expected so i'm going to turn down my indirect lighting again because it's obviously way too strong but now we've got some some good proper gi now that's the reason so lumen uses some kind of ray tracing under the hood even though the light was shining through the window just fine it wasn't the gi aspect of lumen was not able to reach the inside of my apartment scene because of that hdri dome so it's important to keep that in mind this is one of the things i just kind of had to fiddle around with and discovered by accident so hopefully i'm not the only one who ran into this issue hopefully this helps you out or some of you out at least and so guys that concludes this tutorial this was very much a crash course this is not intended to be a full-fledged lumen tutorial this is still early access things are going to change but i figured i'd help you guys kind of figure out what some issue they're renting to are and what those solutions to those issues can be with that being said thanks so much for watching and i'll see you all in the next video

Channel: William Faucher

Views: 124,731

Keywords: UE4, Unreal Engine, Cinematics, 4.26, UE4 4.26, UE5, Realtime, realtime rendering, rendering, CGI, 3D, 3D Artist, Unreal Engine 5, Lumen, tutorial, lumen tutorial, noisy shadows, noise shadows

Id: CFKNoeUPQGQ

Length: 13min 4sec (784 seconds)

Published: Thu May 27 2021