Dubbed FlashBack, the technology is currently in development at Microsoft Research. It is demonstrated in a video uploaded to the experimental division’s website. The technique works to bring low-latency virtual reality to devices without powerful processors.
Microsoft explains how most current smartphones are unable to meet the intensive demands of virtual reality applications due to thermal limits and generally underpowered hardware. Mobile devices typically have an abundance of storage though, whether as internal memory or an SD card.
FlashBack takes advantage of this storage to boost the performance of virtual reality. It generates each possible player view ahead of time and then caches it in the device’s storage. For every reachable position in the environment, FlashBack generates and renders a frame of video for each eye, and then stores this somewhere on the phone.
The colour map for each eye is then combined into a “mega-frame.” This mega-frame is used to rapidly update the virtual reality headset’s view as the player moves around. Each time a new frame is required, FlashBack finds the mega-frame that best matches the new view. It then warps it to fit the headset’s perspective and displays it on the screen, eliminating the waiting time for the graphics processor to deliver a new frame.
“This technique allows even weak mobile devices to quickly and easily reconstruct the scene, without any costly real-time rendering,” explained Microsoft in its video. “We can even support animated objects with arbitrary motion.”
The company claims FlashBack can boost the frame rate of virtual reality apps on mobile devices by up to eight times. It sees a 15x latency reduction and a 100x improvement in energy efficiency. Because the scene only has to be rendered once, the graphics processor has very little work to do once the app is actually running.
There are a few limitations to the technology though. First and foremost is the large amount of storage required. FlashBack essentially caches hundreds of photos in the expectation they’ll be used later on. While the cache is cleared after each run, if a user stores a large amount of media on their phone there may not be sufficient space left to successfully run FlashBack. Heavy compression translates a 4K visual into a 100KB file but across hundreds of such files it could rapidly add up.
Even so, should FlashBack make its way to consumer hardware it could further lower the entry barrier for experiencing virtual reality content. A lot of work has been going into this area recently, ranging from AMD’s $200 VR-ready graphics card to low-cost headsets that in some cases come bundled with smartphones.
As virtual reality becomes more widespread, it’s likely such efforts will grow too. Lowering entry barriers lets more people participate in VR, creating a richer ecosystem that ultimately includes more capable hardware and better-optimised software.
