Credit to Wishmaster92 for picking up the article.

Crytek CEO: Ryse wouldn’t have run at 1080p on PS4

Disclaimer: He is not claiming that Ryse (in its current form) would not be possible to run on the PS4 at 1080p. He is merely stating that 900p upscaled was a design choice. More below

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According to him, things would have been no different, had the game been in development for the PS4. The decision to go with a native resolution of 900p was purely by choice, and not the result of a technical hurdle. He goes on to imply that there is no meaningful loss in image quality due to it not being rendered at native 1080p. Compromising image quality in favor of visual fidelity via enhanced shaders is, in his view, a more efficient solution.

From Gaf.

Sure sure, I believe you buddy.

But if it wasn't due to a technical hurdle then they could have made it 1080p...

Oh well, I really don't care that much because the game looks so fun (and is pure eye candy!)

Sounds more like an issue of time then one of technical issues.

This just in, low res > than high res...

That's believable games gonna look incredible no matter what though.

I wonder if this might be a pattern this gen. Devs want to do more with the new consoles than just put out games that run at 1080p 60fps. They want more realistic graphics, particle effects, lighting, water, more things happening on screen, bigger environments. With all those ambitions the hardware still won't quite be up to doing all those things and 1080p/60fps. Personally I like that sort of compromise, lower the output but put in more details and realism. Heck I'm pretty happy for games to stay at the current 720p/30fps if it gives us more awesomeness in other visual aspects.

i have the feeling that the reason why ryse isn't 1080P is that could do it but that would mean the game might miss the launch of the xbox one

"No perceived visual difference."

There it is, kids. This is what makes and will continue to make all of this nitpicking about specs a complete waste of time, energy and emotion. There will likely be many, MANY games that are upscaled from a lower resolution to 1080p this gen instead of running it natively when the artist and graphics designers realize that they can run games better and the visual difference is indistiguishable off-paper.

Again, get used to it, on both the X1 and PS4. And games will be better for it.

I imagine the design choice was to have the frame rate run smoother.