Saw the video analysis by Digital Foundry. Engine is hard on hardware:
First of all, there's the issue of shader compilation stutter - a problem with UE4 titles on PC for some time now and massively impactful to any initial run through the city sample, no matter how powerful your PC. Once the stutters subside (which they do, the longer you play the demo), it quickly becomes obvious that even a highly capable CPU is struggling with the content. A Core i9 10900K at 5.0GHz locked paired with an RTX 3090 can see a performance average of around 44fps in a fairly taxing scene - and that's at native 720p rendering, attempting to remove the GPU as a limiting factor to performance. Moving at speed through the city sees sharp frame-time spikes: further stutter that seemingly isn't shader compilation limited.
Interestingly, removing hardware-accelerated ray tracing features from Lumen and using software GI as a fallback offers up a significant performance win, presumably because the CPU no longer needs to generate the internal BVH structure - the geometry by which ray traversal is tested. In my tests, using hardware Lumen incurs a 32 percent performance hit. There's room for optimisation and I noted that UE5's CPU scaling is odd - running the 10900K at half speed gives a 40% performance hit. However, running the same CPU with half the available cores/threads only sees performance drop by four percent. This suggests that UE5 performance is more reliant on single-core speed as opposed to exploiting the many cores and threads in a modern PC processor.
The quality of the rendering is superb, Lumen and Nanite are delivering the generational leap in fidelity we want from the latest hardware, but I am concerned about CPU performance, where we can easily find limits even with the most powerful processors on the market. Of course, this is just a demo sample and not a final product but even so, I'm surprised at the apparent reliance on single-thread CPU performance - I'm concerned that attaining 60fps in UE5 titles for PC, let alone consoles, is going to be extremely challenging. However, ultimately, this is just a single example of the engine in action - and of course, the technology remains in a constant state of development, with many improvements to come.
First of all, there's the issue of shader compilation stutter - a problem with UE4 titles on PC for some time now and massively impactful to any initial run through the city sample, no matter how powerful your PC. Once the stutters subside (which they do, the longer you play the demo), it quickly becomes obvious that even a highly capable CPU is struggling with the content. A Core i9 10900K at 5.0GHz locked paired with an RTX 3090 can see a performance average of around 44fps in a fairly taxing scene - and that's at native 720p rendering, attempting to remove the GPU as a limiting factor to performance. Moving at speed through the city sees sharp frame-time spikes: further stutter that seemingly isn't shader compilation limited.
Interestingly, removing hardware-accelerated ray tracing features from Lumen and using software GI as a fallback offers up a significant performance win, presumably because the CPU no longer needs to generate the internal BVH structure - the geometry by which ray traversal is tested. In my tests, using hardware Lumen incurs a 32 percent performance hit. There's room for optimisation and I noted that UE5's CPU scaling is odd - running the 10900K at half speed gives a 40% performance hit. However, running the same CPU with half the available cores/threads only sees performance drop by four percent. This suggests that UE5 performance is more reliant on single-core speed as opposed to exploiting the many cores and threads in a modern PC processor.
The quality of the rendering is superb, Lumen and Nanite are delivering the generational leap in fidelity we want from the latest hardware, but I am concerned about CPU performance, where we can easily find limits even with the most powerful processors on the market. Of course, this is just a demo sample and not a final product but even so, I'm surprised at the apparent reliance on single-thread CPU performance - I'm concerned that attaining 60fps in UE5 titles for PC, let alone consoles, is going to be extremely challenging. However, ultimately, this is just a single example of the engine in action - and of course, the technology remains in a constant state of development, with many improvements to come.