At its State of Unreal event in Chicago, Epic Games officially unveiled Unreal Engine 5.8, and one of its key new features is Lumen Lite: a scalability setting that targets the use of ray-traced global illumination for the Nintendo Switch 2, with the goal of 60 fps. As the feature also works for PCs, I thought I’d dive in and check out just what the fuss is all about. Or if indeed any fuss ought to be made.
By default, the Unreal Engine editor gives developers a simplified way of checking out various graphics settings to see how they affect performance and visual quality. There are 11 separate options that can be tweaked, but the new Lumen Lite mode only affects global illumination (GI) and reflections, as these are the main things that Epic’s ray tracing system affects.
In older versions of UE, switching to ‘Medium’ GI and reflections fully disables Lumen, but in the latest release, the same setting enables Lumen GI, though reflections are still screen-spaced, i.e. SSR. Ray-traced global illumination is normally the preserve of the ‘High’ or ‘Epic’ settings, so to make it more performant for low-end GPUs, Lumen Lite replaces a key stage in the lighting process with something quicker but lower in quality than the usual system.
I first caught a glimpse of this in action via Skydek’s YouTube channel, earlier this year, and the end results looked really promising, as Lumen Light was giving up to 40% more performance for very little difference in visual quality. But watching the demo, set in a fairly simple environment and using software Lumen, I kept wondering how much of a difference it would make when hardware Lumen is used and in a graphics-heavy scenario.
To that end, I fired up Unreal Engine 5.6 and 5.8, and used Epic’s Electric Dreams Environment demo to see Lumen Lite in action. Now, as I’m merely a UE hobbyist, I did nothing more than install all the assets for each UE build and check out the performance in the viewport.
This is very much a ‘worst-case scenario’ or, if you prefer, a ‘Nick is rather lazy’ scenario, as the displayed performance is not even remotely representative of how it would all be in an actual game, and I’ve just clicked a few buttons, rather than directly adjusting the code for the graphics settings and then building the full demo.
Anyway, let’s set the scene, as so to speak, by seeing everything in action in Unreal Engine 5.8, using Epic scalability and materials. It’s not the very highest setting you can use, but in the case of Lumen, it’s for targeting consoles at 30 fps. I’ve used a Core Ultra 270K Plus with a GeForce RTX 4080 Super, so not console-like at all, but as you can see, it certainly looks great, albeit with a rather low frame rate.
Now, let’s take a look at the same situation and settings, except with ‘Medium’ used for GI and reflections, i.e. Lumen Lite. The first thing you should notice is that the performance is roughly 25% better, and the overall lighting is pretty good. Only the screen space reflections spoil the picture somewhat, but that’s what you get for not using ray tracing in those areas.
Before you get your pitchforks out over the fact that Epic says that Lumen Lite is “twice as fast as Lumen High quality”, it’s worth noting that only the GI and reflections processing is twice as fast. What we’re seeing here is that everything else in the UE editor viewport demo is exceptionally heavy, which is why there’s only a 25% uplift, rather than a 100% one.
I was keen to compare UE5.8 and Lumen Lite to UE5.6, as that iteration was notable for targeting more performance across the board, and since ‘Medium’ GI and reflections in this version just disable Lumen altogether, I’d expect to see a big difference in the frame rate for a notable loss in visual fidelity. Well, that’s exactly what I got. In fact, it’s quite remarkable just how bad it looks compared to using Lumen, with heavy flickering across almost all objects.
So I tried it all again, switching to ‘High’ GI but leaving reflections SSR-based by using the ‘Medium’ setting. Notice the immediate improvement in how it all looks? More importantly, can you see that the use of Lumen GI doesn’t hurt the performance too much?
Of course, this is all on a high-end gaming PC, not a Switch 2 or a handheld device like the Steam Deck or ROG Ally. The former has more than enough resources to hand for the ray tracing part of the whole rendering chain to not be a problem, as demonstrated by the difference between Lumen Epic and Medium quality above.
But it did make me wonder whether Lumen Lite is a little bit unnecessary, and that a healthy dose of good old-fashioned optimization will be just as good. If I were a Switch 2 developer, I’d probably say, “No, Lumen Lite is very necessary and a great idea,” because I only have to worry about two hardware configurations: docked and handheld mode.
When it comes to making PC games, it’s a whole different kettle of fish, and while Lumen Lite might be useful as the default mode for ‘Steam Deck’ settings, every other hardware config really needs careful tweaking to account for the differences between the numerous models of AMD, Intel, and Nvidia GPUs that can support Lumen (software or hardware).
If a studio is going to dedicate the necessary time and resources to doing all of that, then they probably won’t use Lumen Lite and instead will fine-tune things by hand, so to speak. However, now that we’re in a period where many studios are being shut down and hardware costs are ballooning, any game devs using UE5.8 will probably just stick to the basics because of time and cost constraints.
Epic almost certainly added Lumen Lite on the basis of feedback from developers, looking for a quick and simple solution to ray-traced lighting on the least capable hardware. Well, they’ve got exactly what they asked for, and it is genuinely useful. I just fear that the ‘one-click solution’ is going to be heavily used instead of what we’d all like to see.
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