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Nvidia's radical multi-resolution shading tech could help VR reach the masses

Brad Chacos | June 2, 2015
Nvidia's new multi-resolution shading tech takes advantage of the way virtual reality headsets render images to enable massive performance savings—which means prettier VR games or VR games on cheaper graphics cards.

"We're going to cut down the resolution [at those edges], we're going to cut down the scaling, and effectively use fewer pixels," says Peterson.

The compressed image is rendered in parallel with the full-resolution center region on Nvidia's Maxwell GPU architecture--and yes, Nvidia says a recent 900-series GeForce graphics card or GTX 750 Ti is required for multi-resolution shading--and then re-warped to appear through the VR headset's lenses with no apparent loss of image fidelity. The concept is somewhat similar to the "foveated rendering" technique explored by Microsoft Research in recent years, which concentrates on rendering only the part of the screen that you're actively looking at in full resolution.

"It's between 50 percent and 100 percent less pixel work [compared to traditionally rendered VR scenes]," says Peterson.

That's insane. Even more insane: The reduced quality edge regions truly aren't noticeable in the final image unless the compression quality is cranked to extreme levels.

Eyes-on with Nvidia's multi-resolution shading

In a closed-room Nvidia demo on an Oculus Rift, Peterson let me compare a scene rendered with MRS and without MRS, enabling and disabling the feature on the fly. Rather than staring at the center of the image, as everyday users would do, I focused my attention on the edges of the screen, where multi-resolution shading's magic happens.

At a 30 percent reduction in pixel work, there was no visible difference with MRS enabled or disabled. There was no drop in fidelity, so sudden jarring sensation or flickering when turning the tech on or off--nothing. It just looked like it should.

In order to truly make the reduced rendering visible, Peterson had to crank the compression up to 50 percent, or half the workload of the same image rendered at full resolution across the board. Only then was the effect noticeable, as a faint shimmering around the very edges of the image. The effect was minimal, however, and that's when I was specifically looking for it on the edges. When staring at the center of the display, which was rendered at full fidelity, the compressed resolution at the edges could only very barely be seen, no doubt thanks to the way the human eye views images in our peripheral vision with far less detail than what we're directly looking at.

That's big news for VR developers, and for gamers who want to get into the virtual reality experience without spending the equivalent of a college education on a graphics card.

"So if you're a game developer, this means that you can have higher quality games, or that you can have your games run on more GPUs," says Peterson.

And just like that, the Oculus Rift's GTX 970 requirement didn't feel quite as paltry as it did when the headset's specs were released.

 

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