The concept of native resolution is becoming less and less relevant in the modern era of games and instead, image reconstruction techniques are coming to the fore. The idea here is remarkably simple: in the age of the 4K display, why expend so much GPU power in painting 8.3m pixels per frame when instead, processing power can be directed at higher quality pixels instead, interpolated up to an ultra HD output? Numerous techniques have been trialled, but Kojima Productions’ Death Stranding is an interesting example. On PS4 Pro, it features one of the best checkerboarding implementations we’ve seen. Meanwhile, on PC, we see a ‘next-gen’ image reconstruction technique – Nvidia’s DLSS – which delivers image quality than native resolution rendering.
Checkerboard rendering as found in Death Stranding is non-standard and it’s the result of months of intensive work by Guerrilla Games during the production of Horizon Zero Dawn. Curiously, it does not use PS4 Pro’s bespoke checkerboarding hardware. Base resolution is 1920×2160 in a checkerboard configuration, with ‘missing pixels’ interpolated from the previous frame. Importantly, Decima does not sample a pixel from its centre, but from its corners over two frames. By combining these results over time in a specialised way similar to the game’s TAA and a very unique pass of FXAA, a 4K pixel grid is resolved and the perception of much higher resolution is achieved. According to presentations from Guerrilla, of the engine’s 33.3ms per-frame render budget, 1.8ms is spent on the checkerboard resolve.
Although it upsamples from a much lower resolution, DLSS works differently. These is no checkerboard, no pixel-sized holes to fill. Rather, it works more like accumulation temporal anti-aliasing, where multiple frames from the past are queued up and information from these frames is used to smooth lines and add detail into an image – but instead of adding detail to an image of the same resolution as TAA does, it generates a much higher output resolution instead. As a part of these frames from the past, motion vectors from those frames for every object and pixel on screen are integral for DLSS working properly. all of this information is used to create the upscaled image is decided upon by an AI program running on the GPU, accelerated by the tensor cores in an RTX GPU. So while DLSS has fewer base pixels to work from, it has access a vast amount of compute power to help the reconstruction process.
On an RTX 2080 Ti at 4K, DLSS completes in around 1.5ms – meaning it’s faster than checkerboarding on PS4 Pro. However, the hardware comparison is obviously lopsided. The weakest capable GPU is the RTX 2060 (still significantly more powerful than the Pro) and DLSS has an overhead in excess of 2.5ms on this card. That’s heavy, especially if you’re targeting 60fps where the entire frame rendering budget is just 16.7ms. However, the core advantage is that the base resolution is so much lower. DLSS in Death Stranding comes in two flavours: the performance mode achieves 4K quality from just a 1080p internal resolution. Meanwhile, the quality mode delivers better-than-native results from a 1440p base image. In both cases, that’s much lower than PS4 Pro’s 1920×2160 core resolution. By running in the GPU pipeline at much lower resolutions, the cost of processing DLSS is more than offset – to the point where mildly overclocking the RTX 2060 allows Death Stranding to deliver 4K gaming at 60fps.