What is foveated rendering, and why can it make PSVR 2 streams blurry?

Pushing high-end graphics in virtual reality is a demanding endeavour for any VR headset processor, whether it’s a standalone headset, a high-end PC or the PS5 and PSVR 2. It’s made harder still for PSVR 2 by the high-end specs of the headset and the new expectation for high resolution gaming. So, how does the PS5 pull it off, and why doesn’t it always translate to what you can see in YouTube and Twitch streams?

One of the tricks that PSVR 2 leans upon when render virtual reality is called foveated rendering. You’ll see this term used in a lot of bullet point lists when games are being upgraded or ported to PSVR 2, alongside noting support for 4K and HDR. It’s a lot of attention for a rather technical feature to get, but what is it?

To put it simply, foveated rendering is a way to reduce image quality for parts of the screen that are in your peripheral vision. The game can prioritise where it’s spending the most hardware resources to get the best performance and visual effect for the player.

Horizon Foveated Rendering

Focusing on the target with my bow, Horizon Call of the Mountain uses foveated rendering to lower the resolution elsewhere, most noticeable on the blurrier barrels and settlement in the top left.

It’s all based on real life. When you focus your vision on a cup on a coffee table, for example, the rest of the room that is outside that central focal point is less clear to your eyes and brain. Foveated rendering simulates that effect in VR, allowing the game engine to reducing detail and resolution in places that you aren’t looking.

This has been used since the very start of the current era of virtual reality gaming in 2016, but was initially done in a more rudimentary fashion by locking the focus point to the direction of the headset. Some headsets since the Vive Pro Eye in 2019 have included an internal camera to track eye movements – a key feature for PSVR 2 – allowing for games to more dynamically shift the rendering focal point to better match what you’re actually looking at.

This effect is practically unnoticeable within PSVR 2 itself. The very edges of your field of view are always going going to be a bit blurred and distorted because of the image passing through the Fresnel lenses in the headset, but within that central area there’s still plenty of space to optimise what is being given the most attention – wherever you move your eyes to will then have the game’s highest resolution and level of detail.

But foveated rendering is laid bare to people watching PSVR 2 streams and video capture, and adds to the challenge of making a pleasant viewing experience – the other being that the view can move, shake and judder even if you think you’re keeping your head still. Different parts of the screen are going in and out of higher and lower resolution, matching the player’s eye movements, and that can naturally lead to the snap judgement that the game resolution is low and the graphics fuzzy. Now, there is a natural softness to the player as the image is passing through a lens – even when in the sweet spot, the headset won’t be quite as sharp as getting up close to a 4K TV – but VR games on YouTube will always have parts of the screen look blurrier and lower resolution than they do to the person playing.

In some ways this makes the 4K claim that games make a bit of a lie – similar to the dynamic resolutions that are so often used for flat screen games. Claiming 4K is really just using an easily understood term to convey something much more complex, the notion that you’re getting 4K-like rendering at the things you are specifically looking at.

It’s all part of the difficult challenge that developers and users face in trying to show and explain what VR gamers are like, without putting a headset on someone and sending them on their way. Just rest assured that foveated rendering might look a bit rough in a stream, but it’s all in aid of making the actual games look and feel as good as possible in VR.

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1 Comment

  1. I noticed the blurry bits in the GT7 VR announcement trailer, most noticeable on the steering wheel when the player looks elsewhere.
    I’ve tried looking very quickly from edge to edge to see if I could view the lower res areas but it’s always too fast for me. It can also track where you’re looking with your eyes closed.

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