Guerrilla Games’ Horizon Zero Dawn not usually lifted a bar in terms of technical fulfilment on stream era console hardware, it handed in a best 4K HDR arrangement we’ve seen from any PlayStation 4 Pro title. The local 1080p outlay on bottom hardware beam adult to 2160p on Pro, regulating a tradition doing of checkerboard rendering, nonetheless Horizon’s arrangement is so clean, so solid, so convincing, it passes for a ‘real thing’ – so how was this achieved?
A while back, Digital Foundry spent a day with Guerrilla Games in Amsterdam, deliberating a technological make-up of a game, a revisit kicking off with an in-depth speak with principal tech operative Giliam de Carpentier on how a studio got to grips with a PlayStation 4 Pro hardware.
“Well, let’s start during a unchanging 1080p year digest – we have a clever concentration on anti-aliasing so whatever technique we wanted to use for carrying 4K digest also indispensable to be during that same quality,” says de Carpentier. “And apparently a PS4 Pro is a lot some-more comprehensive than a customary PS4, nonetheless digest natively would have been too many to ask, perhaps.”
Pro and HDR support was integrated into Horizon comparatively late into a game’s six-year development, and Guerrilla experimented with several aloft fortitude strategies, perplexing them out corresponding before settling on 2160p checkerboard. In terms of local rendering, a group gave 1500p a shot, nonetheless weren’t wholly confident with a results. And to be clear, checkerboarding in a box of Horizon involves digest half of a pixels for a full 2160p frame, a other half fortitude around reprojection from a prior support – a routine that Giliam says provides a “native fortitude fact level”, if not quite a sharpness. However, any natively rendered pixel – be it 1080p on bottom PS4 or checkerboard 2160p on Pro – also advantages from 4x temporal super-sampling.
“We resolved for us [that] it finished clarity to go for a routine of digest that gave us a many fact – given interestingly adequate even nonetheless we usually describe 50 per cent of a pixels on any frame, after dual frames we do get a fact level, nonetheless not per se a same sharpness as [native] 4K,” explains de Carpentier. “There are maybe ways to also do that nonetheless we concentration generally on a detail, so compared to maybe a unequivocally serious or a unequivocally purify 4K local digest of a CG theatre we theory a diversion doesn’t have that same crispness, nonetheless afterwards again if we demeanour during a customary 4K film it doesn’t have that compactness either. If we demeanour during a edge-lines they are typically like dual or 3 pixels thick.”
So how do we compute sharpness contra detail? Well, checkerboard or not, regulating during 2160p helps to safeguard that aloft mip turn textures are streamed in – something that’s not indispensably a box when handling during a reduce local resolution. Also, cruise that pixels alien and reprojected from a prior support are theme to a same 4x temporal super-sampling as those in a stream frame. Horizon retains fact and crucially, around this treatment, it does so all a approach into a distance.
“For a anti-aliasing we cite to use 4 samples per pixel, we also do that during 1080p,” explains Giliam. “That’s given all of a leaflet is alpha tested. Individual leaves of weed can be reduction than half a pixel wide, so we get all arrange of jumpy artefacts in a stretch that can be irritating to work with. We figured out with 1080p that 4 samples per pixel – 4 times super-sampling – is a minimum. We also use dual frames of consecutive animation for anti-aliasing in 1080p that is usually a movement of temporal reprojection.”
The change in terms of fact vs sharpness adjusts a hold when we review a PS4 and Pro versions of a game. The bottom PlayStation 4 runs Horizon during local fortitude with 4x super-sampling, so that 1:1 pixel map produces an arguably crook picture than Pro. However, checkerboarding to 2160p on a some-more comprehensive console trades a small sharpness, nonetheless offers a big, large win in terms of detail.
“It’s a bit of a quality/quantity trade-off we can make,” muses de Carpentier, “[You could have] 1800p checkerboard digest in a box during least, with some-more whistles and bells trustworthy to it, so we could have some-more sharpness in those 1800p checkerboard pixels contra a small reduction sharpness in 2160p checkerboard – nonetheless we do have 2160p so we do have that small additional fact in a geometry and a textures.”
A good instance of how additional fact feeds into a Pro chronicle diversion comes from anisotropic filtering. Our initial research suggested that textures benefitted from aloft levels of AF, nonetheless this is not indeed a case. At 2160p – checkerboard or not – some-more hardness is sampled, definition that a same hardness filtering produces distant some-more minute results.
On tip of that, interface and HUD elements are rendered during local 2160p, sucking adult some of PS4 Pro’s additional 512MB of RAM, nonetheless a team’s plan was to open adult as many of a additional memory as probable to a game’s streaming systems – to safeguard that a tip peculiarity versions of any hardness solve wherever possible, again adding to a additional fact turn found in a Pro game.
So, what about HDR? Going behind to a PS3 days, Guerrilla has championed high-dynamic operation rendering, tone-mapped down for final sRGB output. Surely HDR support should be sincerely elementary to exercise afterwards – during many simple level, it would simply be a box of slicing out a tone-mapping stage. It turns out that this is not a box – Guerrilla’s games are shabby severely by art direction, and post-process aspects such a colour grading are traditionally finished in SDR – it’s a improved fit for a team’s workflow and there are other logistical reasons too.
“Most of a users are substantially regulating SDR so we wanted to keep that as a categorical aim to colour scold for,” says Giliam. “It doesn’t meant we didn’t wish to give HDR a suitable time to also be tweaked, nonetheless we did feel it was improved to concentration on SDR and afterwards modify to HDR.”
The acclimatisation routine radically adds an additional ‘sparse’ channel of information in a acclimatisation behind to HDR – a complement that not usually works for a game’s rendering, nonetheless also for a title’s video sequences, all of that are local 4K, with a same item regulating on both PS4 and Pro hardware. Managing a stretch of a HDR channel was an emanate though, some-more so than any intensity opening implication.
“Bandwidth-wise we have to be unequivocally clever when handling your buffers – not to get additional colour-banding, for instance – given a additional pieces do take adult bandwidth and generally when you’re also perplexing to do 4K, it unequivocally matters. Every bit matters, so we have to be unequivocally clever with formulation your whole pipeline, your post pipeline, in sequence to not get serious colour banding.”
Further issues finished HDR growth severe – privately a miss of a singular anxiety arrangement for HDR output. There is no genuine customary out there, and any display, any user gets a opposite experience. At rise brightness, Horizon outputs 6000 nits when looking directly during a sun, while a shade like LG’s glorious B6 arrangement – for a money, a best cost vs opening shade on a marketplace right now – usually has a rise liughtness of 560 nits. Even Sony’s possess flagship ZD9 maxes out during 2400 nits. Tuning HDR for Guerrilla was a plea given in pulling HDR as distant as they could, a developer is literally incompetent to see a effect.
Guerrilla’s HDR work finished adult gaining opening for a diversion after a doing as against to losing it, and as remarkable in a initial research of a launch code, bottom PS4 and Pro run effectively equally – even nonetheless a dual sets of hardware have unequivocally opposite bottlenecks. Again, it’s a doubt of balance: Pro might usually have an incremental boost in memory bandwidth, nonetheless other areas of a GPU offer generally thespian improvements to hardware performance.
“We have a flattering low tube with a abyss primary and a geometry category like a customary deferred renderer, and a lighting pass and a lot of post effects,” de Carpentier explains. “For us, a abyss primary in a geometry and a lighting was faster even in checkerboard local than it was on 1080p on base, so that combined some headroom to get a bit some-more out of a post effects.”
However, fortitude a checkerboard to full 4K nails behind some of those opening wins, and bandwidth becomes some-more of an emanate as regulating during a aloft fortitude requires a developer to representation some-more hardness data.
“There are opposite ways to do checkerboarding as well,” adds Giliam, who told us that they ‘rolled their own’ fortitude as against to regulating Sony’s anxiety model. “You can have some-more information per pixel, or reduction information per pixel when digest checkerboarding and depending on how many information we have, we can go for opposite checkerboard solve techniques. We came adult with one that doesn’t need a lot of additional information during a per-pixel turn and that gave us some opening boosts as good in a digest of a whole geometry and a lighting pass.”
While a concentration on Horizon’s Pro support is a best-in-class 2160p checkerboarding, there is a opening mode too. Typically, options like this on other titles have an unbarred frame-rate – and a existence is that unequivocally few games with this mode have managed to burst from 30fps to a sealed 60fps. Horizon retains a 30fps close in a opening mode, a thought being to offer a totally rock-solid close during this series from start to finish. Horizon is built on a 30Hz engine that already taps out a CPU roughly wholly – unlocking a frame-rate would not have worked for this title.
As things stand, any leftover CPU time is spent on pre-emptively streaming in universe information – a complement that removes a kind of stumble we mostly see during traversal in many open universe titles. The aim here afterwards is comprehensive fortitude – there’s an additional 10 per cent of beyond left over to safeguard unchanging opening in a many severe areas. Native fortitude shifts adult to 1368p and there are a integrate of peculiarity advantages too as checkerboarding is not in a mix. Principally, volumetric and abyss of margin passes scale adult in line with a pixel count.
But it’s a high fortitude mode that provides a best triple-A 4K knowledge we’ve enjoyed nonetheless on console. There’s no concede on coherence – even Horizon’s pre-rendered cinematics run during 4K with HDR – while a team’s concentration on fact and anti-aliasing pays off. Foliage, weed and other sub-pixel fact solve distant into a distance, with nothing of a break-up or shimmering we would differently get. Meanwhile, Guerrilla’s checkerboard solve – a tradition various grown by a studio itself – is best in class: break-up and cross-cross artefacts are probably unfit to spot. And it opens adult an engaging debate: when a next-gen consoles finally arrive in a integrate of years, should GPU resources be spent on ‘true’ 4K outputs when technologies like temporal supersampling and checkerboarding can demeanour this good operative in tandem? Horizon Zero Dawn creates a constrained box that we can have a cake and eat it – that we can trade a small sharpness for a large win in terms of visible ambition.
Digital Foundry trafficked to Guerrilla Games in Amsterdam to cover this story. Sony paid for transport and accommodation. If you’re meddlesome in a deeper tech low dive into a Decima Engine’s anti-aliasing and checkerboarding techniques, we rarely suggest checking out Giliam de Carpentier’s Siggraph presentation.