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Do we need 4K resolution for immersive VR?
For a truly immersive virtual reality experience, the screens on emerging head-mounted displays need a much higher resolution than is currently available, but how many pixels is enough?
October 29, 2013
5 Min Read
Oculus HD and Beyond
Shortly after shipping 10,000 developer kits, the folks at Oculus announced that they had made an HD Prototype of the Rift that has a 5″ screen and a resolution of 1920 x 1080. Oculus set up a booth at the IndieCade conference this month to let patrons try out the HD model on the winners of the VR Jam. This was my first opportunity to test out the prototype and in both of my experiences with it (playing Virtual Internet Hacker and Dumpy), I did not notice the decreased screen size (from 7 to 5in), but definitely noticed the increased number of pixels. The edges of objects were still rough and I would not call the image crisp, but without a visible grid of pixels, there was no screen door effect that you get with the developer kits.
Overall, the HD prototypes provided a more pleasant VR experience than the developer kits because of the increased pixel density and decreased size, but they were still nowhere close to the quality necessary for a truly immersive experience. They need a significantly higher resolution in a screen so close to your face... and they know it. They recently announced that they are working on a version of the Rift with a 4K (3840 x 2160) resolution display, but will that be enough?
Pixels Per Inch
As screens get bigger, the pixels that make up the image get bigger. With the same resolution, the pixels that make up a 50″ TV’s image will be much larger than that of a 32″ TV’s image. So when Oculus showcased their 5″ prototype with a higher resolution than the 7″ model, the pixels are dramatically smaller, and the pixelation effect is far less apparent. The standard measure of pixel density is pixels per inch (PPI).
The folks at ifixit took apart a developer kit to see what it was made of and found that it was using a “Innolux HJ070IA-02D 7″ LCD.” This 7″ display has a resolution of 1280 x 800 and provides 215 PPI. The Oculus splits the screen in half so each eye is only seeing 640 x 800. The HD prototype has a 5″ screen with a resolution of 1920 x 1080 (960 x 1080 per eye) for a PPI of 440. So in just a year, they have more than doubled the PPI of the device by decreasing the screen size and increasing the resolution. It was still not nearly enough to remove the pixelation effect, but it shows they are moving in the right direction.
One big advantage that the virtual reality peripheral manufacturers have is being able to share R&D efforts with smartphone and tablet manufacturers. Everybody is trying to put more pixels into smaller packages. Right now, there is a lot of talk about the resolution of handheld display resolutions and the marginal benefit of “retina displays”. Some argue that we do not need to keep increasing the resolution of these devices because the human eye cannot distinguish additional pixels at the distance that most people use their cell phones (about 12-18in), while others welcome any increase in resolution. Either way, all of the major manufacturers are pushing for more pixel density, and that is great news for fans of virtual reality.
8K Per Eye
Unlike large television sets many feet away, with a screen only inches from your face, any additional pixels make a dramatic difference to the quality of the image and the immersive effect. To answer the title of this post, Do We Need 4K Resolution For Immersive Virtual Reality? No. For a truly immersive virtual reality experiencewe need much more than 4K resolution!
Palmer Luckey, the founder of Oculus, made a comment that he thinks the pixelation effect will not go away until the resolution reaches beyond 8K (7680 x 4320) per eye. From an Arstechina article:
“To get to the point where you can’t see pixels, I think some of the speculation is you need about 8K per eye in our current field of view [for the Rift],” he said. “And to get to the point where you couldn’t see any more improvements, you’d need several times that. It sounds ridiculous, but HDTVs have been out there for maybe a decade in the consumer space, and now we’re having phones and tablets that are past the resolution of those TVs. So if you go 10 years from now, 8K in a [head-mounted display] does not seem ridiculous at all.“
I agree. With the current rate of progression for screen resolution (with 4K coming to tablets and 8K TVs on the immediate horizon) the idea of a very small 8K screen is not far away. For a more detailed look at the current status of the Oculus screen resolution, there is a post on the oculus developer forum that goes very deep into the current and optimal resolution for perfect virtual reality with the Oculus. While some of his analysis is difficult to follow, the author uses Field of Vision (FOV) and Angular Pixel Density (APD) measurements to conclude that:
“If we want the “perfect” Oculus Rift, with 180 degrees FOV and an APD of 45, we’ll need a screen with a resolution of 8000 x 4500″
This matches up very well with Luckey’s comment of 8K per eye. Using a PPI calculator, a 7″ screen with resolution of 8000 x 4500 would require 1311 PPI. The highest PPI of any display developed so far is 651 PPI on a 2″ screen by a company in Japan. So if you are looking for a truly immersive virtual reality experience, give it a few years.
For more information on gaming in 4K Ultra HD and beyond, check out my blog at 4KGamer.com.
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