Epic’s reveal of Unreal Engine 5 running in real-time on PlayStation 5 delivered one of the seismic news events of the year and our first real ‘taste’ of the future of gaming. A true generational leap in terms of sheer density of detail, alongside the complete elimination of LOD pop-in, UE5 adopts a radical approach to processing geometry in combination with advanced global illumination technology. The end result is quite unlike anything we’ve seen before, but what is the actual nature of the new renderer? How does it deliver this next-gen leap – and are there any drawbacks?
Watching the online reaction to the tech trailer has thrown up some interesting questions but some baffling responses too. The fixation on the main character squeezing through a crevice was particularly puzzling but to make things clear, this is obviously a creative decision, not a means to slow down the character to load in more data – it really is that simple. Meanwhile, the dynamic resolution with a modal 1440p pixel count has also drawn some negative reaction. We have access to 20 uncompressed grabs from the trailer: they defy traditional pixel counting techniques. When the overall presentation looks this good, this detailed, with solid temporal stability (ie, no flicker or shimmer frame to frame), resolution becomes less important – the continuation of a trend we’ve seen since the arrival of the mid-generation console refreshes. As we said almost two years ago now, next-gen shouldn’t be about ‘true 4K’, the game has moved on and put it frankly – GPU resources are better spent elsewhere.
Some interesting topics have been raised, however. The ‘one triangle per pixel’ approach of UE5 was demonstrated with 30fps content, so there are questions about how good 60fps content may look. There have also been some interesting points raised about how the system works with dynamic geometry, as well as transparencies like hair or foliage. Memory management is a hot topic too: a big part of the UE5 story is how original, full fidelity assets can be used unaltered, unoptimised, in-game – so how is this processed? This, in turn, raises further questions about the storage streaming bandwidth required, an area where PlayStation 5 excels. So, to what extent is the Lumen in the Land of Nanite tech demo leveraging that immense 5.5GB/s of uncompressed memory bandwidth? Hopefully we’ll learn more soon.
Core to the innovation in Unreal Engine 5 is the system dubbed Nanite, the micro-polygon renderer that delivers the unprecedented detail seen in the tech demo. The concepts of the micro-polygon engine aren’t new – they are used extensively in movie CGI. The starting point is the same, but the execution in games is different. Models are authored at that same very high quality with millions of polygons per model, but no lower quality models with bespoke normal maps are created for in-game usage. In Nanite, the geometric detail of that high quality model is scaled up and down in real time. Higher detail does not have to be filled in with a baked out normal map – the previous way game models were made. Key Epic Games staff members helped to further our understanding of the technology by answering a few key questions.
“With Nanite, we don’t have to bake normal maps from a high-resolution model to a low-resolution game asset; we can import the high-resolution model directly in the engine. Unreal Engine supports Virtual Texturing, which means we can texture our models with many 8K textures without overloading the GPU.” Jerome Platteaux, Epic’s special projects art director, told Digital Foundry. He says that each asset has 8K texture for base colour, another 8K texture for metalness/roughness and a final 8K texture for the normal map. But this isn’t a traditional normal map used to approximate higher detail, but rather a tiling texture for surface details.