Sony announced the new Project Morpheus prototype at GDC with vastly improved specs. One of the things that really stood out was that Project Morpheus will support a frame rate of 120 fps — far more than competing headsets from Oculus and HTC/Valve.
While both the HTC Vive and Oculus Rift have a frame rate of 90, Sony’s VR headset will push that number to 120 — and all games will always run at 120 fps. How does Sony do this? With a proven technology called reprojection.
What is reprojection?
One of the pitfalls of virtual reality headsets is judder and blur, which occurs when you move your head faster than the image can render the next frame. A common result of that is motion sickness.
Both Oculus and Valve think that 90 frames per second is enough to alleviate any sense of motion sickness, but Sony isn’t taking any chances — they’re pushing for a steady 120 fps at all times. And they’ll achieve this with reprojection and a very low latency (under 18ms).
Reprojection creates an additional frame between the first and second frame, this way, 60 fps becomes smoother 120 fps. In fact, Sony has confirmed that reprojection will always be on, even if the game runs at 120 fps natively. This is to ensure that it’s always 120 fps no matter what.
Sony’s Shuhei Yoshida said that reporjection won’t require too much from the system to run. As he puts it, “It runs right at the very end, just before the frame is going to be displayed. It interrupts the GPU and does this little bit of work.”
Does this mean the image won’t look as good?
Sony’s reprojection software takes data from the first and second frame, and creates an average of the two, putting it in between. Since the images are moving so fast — 120 times per second — it’s hard to tell the difference. It would be more pronounced if reprojection was used to bump a 30 fps game to 60 fps.
Running at 120 fps natively instead of using reprojection would be preferred, but the current PS4 hardware won’t be up to the task unless image quality is sacrificed. The good news is that reprojection isn’t a novel technology.
In fact, reprojection has proven itself before and Sony has a lot of experience with it — they use a similar technology in their 3D movies with their Sony Pictures Studios.
Benefits of reprojection
The main benefit of reprojection is that developers don’t have to scale down on image quality in order to hunt higher frame rates. We already know that 60 fps and 1080p is pushing what the PS4 hardware can do.
Plenty of PS4 games are running at 60 fps at 1080p, and developers will now have an easier time to port those games to Project Morpheus without having to sacrifice too much.
Sony’s aim for 120 fps at all times sets a solid benchmark for virtual reality headsets. However, reprojection isn’t limited to the PlayStation 4 — the HTC Vive and Oculus Rift could add a similar feature with support from PC graphics makers AMD and Nvidia.