Unreal Engine 5 recently launched into Early Access, and the full version is now available to game creators. At the same time, the “City Samples” section of the fantastic The Matrix Awakens demo was also released, giving users the opportunity to master MetaHuman crowds and large-scale AI in a vast open world, with buildings, roads, and more procedurally creating a generation. In short, Epic is opening up tons of amazing new technology to everyone, and UE5 is actually the first paradigm shift in game development since the new consoles came out. So what have we learned from this release? In short: the demands are high. Very strict.
At this point, it’s worth highlighting why the urban sample is so special — and very simple. Creating and rendering cityscapes with this level of detail is no walk in the park. Previous UE5 demos were limited to linear, unity, rocky landscapes. Cities like the ones here “given” are far more complex in terms of materials, shapes, forms and dynamism. The Nanite geometry system provides extreme detail to the smallest elements in the city – so much so that individual tiny assets appear almost to life when viewed up close. Nanite has its limitations when it comes to animated characters or deformable meshes like cars, while integrating elements like plants is still a work in progress (though it’s definitely in the pipeline!). However, the results in this demo speak for themselves.
Then there’s the Global Illumination System – Lumen – now with updated support for diffuse GI and hardware triangle ray tracing for reflections. In some cases Lumen’s non-RT fallbacks look almost as good, but in others it’s clear that RT can make a huge difference – reflections are more accurate and detailed, lighting is more accurate, especially noticeable at night – time scene.
Here’s Alex Battaglia’s in-depth look at UE5 features and the performance implications of this rendering paradigm shift.
Epic is pulling out all the stops here – at least for now, and the performance impact can be surprising. The first is the issue of stuttering shader compilation – UE4 titles have been an issue on PC for a while now, and no matter how powerful your PC is, it can have a huge impact on any initial run of city samples. Once the stutters subside (and they do, the longer you play the demo), it quickly becomes apparent that even the powerful CPU is struggling to process the content. The Core i9 10900K locked to 5.0GHz with the RTX 3090 saw around 44fps average performance in fairly heavy scenes – this is at native 720p rendering in an attempt to remove the GPU as a performance limiting factor. Moving quickly through the city sees noticeable frametime spikes: further stuttering that doesn’t seem to be limited by shader compilation.
Interestingly, removing the hardware-accelerated ray tracing functionality from Lumen and using software GI as a fallback provides a significant performance boost, probably because the CPU no longer needs to generate the internal BVH structure – the geometry used to test ray traversal structure. In my tests, using the hardware Lumen resulted in a 32% performance drop. There’s room for optimization, and I’ve noticed that UE5’s CPU scaling is weird – running a 10900K at half speed has a 40% performance hit. However, running the same CPU with half the available cores/threads only drops performance by 4%. This suggests that UE5 performance is more dependent on single-core speed than taking advantage of the many cores and threads found in modern PC processors.
The perception is that Unreal Engine 5 is heavy on the GPU – which is likely to be the case, but it’s hard to say when the CPU limit was so easy to hit. My solution here is to turn off the in-city AI for sharper numbers, test the RTX 2060 Super at native 1080p, and use temporal super-resolution to settle for 4K output. I found the hardware Lumen had a 7% performance cost compared to the less precise software equivalent – not bad considering the huge increase in fidelity. Same 7% as the RTX 3080, rising to 17% on the equivalent Radeon RX 6800 XT. Interestingly though, looking at the entire demo, the 6800 XT was about 3% slower than the 3080 overall.
So, where does all this put a mid-range PC? At least for now, the mainstream favorite — the Ryzen 5 3600 — is severely CPU-bound, averaging 30fps in static scenes, but drops even lower when moving. With that in mind, how does Epic make the console version work better? Well, let’s keep in mind that even with specific optimizations, we’re still far from locked at 30fps, but even then Epic’s TSR upscaler doesn’t seem to provide the exact same level of quality as PC reproductions — which means either Quality lower TSR or lower base resolution.
Then there are changes in some quality parameters – reflection distance and general internal resolution seem to be consistent with PC settings high, but there are times when light leaks indicate quality compromises or other optimizations for consoles that don’t exist on PC high settings. It also seems to run at quarter resolution when motion blur takes up most of the screen. Finally, there’s the quality of virtual shadow maps, where the console runs in what looks like a custom half-resolution bias, offering a lower fidelity than the PC’s medium preset.
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With all of this in mind, let’s take a first look at the release version of Unreal Engine 5, what’s our stance? Rendering quality is excellent, and Lumen and Nanite deliver the fidelity leaps we’d hope for with the latest hardware, but I’m concerned about CPU performance, even with the most powerful processors on the market, we can easily find limitations. Granted, this is just a demo sample, not a final product, but even so I’m surprised by the apparent reliance on single-threaded CPU performance – I’m concerned about hitting 60fps in UE5 games on PC, let alone consoles, will be extremely challenging. At the end of the day, however, this is just one example of how the engine works – of course, the technology is still in a state of continuous development, with many improvements to come.
We’ll be tracking the progress of this exciting technology and look forward to seeing the first games using Unreal Engine 5 and its cutting-edge features.
