How Guerrilla bent the rules to turn Horizon into a 4K masterpiece

Digital Foundry has posted a fascinating interview with Horizon Zero Dawn developer Guerrilla Games that details how the studio created one of the PS4 Pro's most impressive 4K titles. 

What's particularly interesting about Horizon is how the team used checkerboarding to render 4K detail across two frames, which is still two times more pixels per frame than native 1080p. But how and why did the studio bend the rules to such great effect? 

Well, according to Guerrilla's principal tech engineer, Giliam de Carpentie, it was a decision borne out of neccessity.

"We have a strong focus on anti-aliasing so whatever technique we wanted to use for having 4K rendering also needed to be at that same quality," explains de Carpentier. "And obviously the PS4 Pro is a lot more powerful than the standard PS4, but rendering natively would have been too much to ask, perhaps."

The team did give native 1500p rendering a shot, but the results were mixed at best. And after plenty of other failed experiments, they finally decided to use a custom implementation of checkerboard rendering, which involves rendering half of the pixels for the 2160p frame, while the other half are pulled from the previous frame.  

"We concluded for us [that] it made sense to go for the method of rendering that gave us the most detail -- because interestingly enough even though you only render 50 per cent of the pixels on each frame, after two frames you do get the detail level, though not per se the same sharpness as [native] 4K," continues de Carpentier. 

"There are maybe ways to also do that but we focus mainly on the detail, so compared to maybe a really rough or a really clean 4K native rendering of a CG scene I guess our game doesn't have that same crispness, but then again if you look at a typical 4K movie it doesn't have that crispness either."

To find out more be sure to check out the full interview over on Digital Foundry (via Eurogamer).

Correction: Our original article incorrectly stated that Horizon Zero Dawn upscaled 1080p to 4K, however, developer Gurrellia has since pointed out that the game does in fact render native 4K across two frames. The story has been updated to make that clear.