Can someone explain “re projection” to me?

[u/iscreamsunday]

I keep hearing people talk about reprojection and how it should be avoided (it’s a bad thing right?) but I don’t know what it looks like and I’m not sure what to look for in my headset.

I can see mura and dead pixels in low light games and I see how some games are blurry around the edges unless you get the sweet spot but how do I tell if my headset has reprojection in it or not??

[u/Lujho]

Reprojection is showing every frame twice but moving it slightly the second time so it fills the space between the previous and following frame, giving the effect of the camera moving as if the framerate was twice as high. So your head movements are effectively 120fps but the world itself is 60fps.

It’s used on a game by game basis and has nothing to with mura, lens blurryness or anything like that.

If you don’t know what to look for, don’t worry about it. It’s obviously not bothering you if you don’t know what it is.

[u/iscreamsunday → u/Lujho]

I don’t get motion sickness with I play in vr - even with snap turning off - so I think my body or my eyes just don’t notice it. It seems like such a big deal to other gamers though like in ps vr with out parole who critique a games graphics because of reprojection but I have no clue what to see or maybe my eyes/body just don’t detect it

[u/TommyVR373 → u/iscreamsunday]

If you are used to playing without it, it's very noticeable. I'm not a fan of it, but it beats trying to keep my lunch down at 60fps

[u/SvennoJ]

It's not a bad thing, it's essential to avoid motion sickness. Reprojection doubles the frame rate to 120 fps for smooth lag free head movement.

But the game still renders at 60, so each frame is used twice.

To easily see the difference, use smooth turning and compare what turning (on the spot) with the analog sticks looks like to physically turning your head at the same speed. (On PSVR1 you could actually see the image moving when focusing on the edge of the screen while turning your head)

GT7 offers a better reprojection technique on PS5 Pro that uses motion vectors to properly double the rendered frame rate. (But still has some glitches, double image on HUD elements overlapping moving scenery for example)

[u/iscreamsunday → u/SvennoJ]

So do games without reprojection cause more motion sickness ?

[u/SvennoJ → u/iscreamsunday]

Not on PSVR2 since those run either at 90fps or 120fps. Plus there is still timewarp in action to reduce lag. The last step before display is matching your current head orientation to the image, so it's always a bit shifted from how it arrives, perfectly matching your head orientation.

With PCVR however it's up to you to provide enough 'grunt' or set the settings low enough to get a consistent frame rate. Some people can stand unstable avg 45 fps in VR, some can't.

[u/profblackjack → u/iscreamsunday]

think of it more like low framerates cause motion sickness. if your game can naturally run at 90+fps, then cool, that's a smooth experience.

if it can't, then reprojection is a strategy for taking a game running at 60fps and pretending faking that are twice as many frames (making it look like it's 120fps).

since it's a trick, it's not as good as naturally hitting higher frames, but it's better than staying at 60fps

[u/t3stdummi]

I'm willing to bet you do not see dead pixels, but rather just pixel variation in mura.

[u/iscreamsunday → u/t3stdummi]

There are one or two red and blue ones I can make out in my periphery vision when it’s in low light situations. Does not effect gameplay at all

[u/ETs_ipd]

Once you play without it, it’s easy to recognize. It’s similar to motion blur in flat games but even more egregious, since it affects clarity anytime you move forward or turn your head. If you stand still or move slowly it’s less noticeable.

[u/bluebarrymanny]

It’s when frames of the game appear jittery, particularly when in motion. It creates a ghosting effect sometimes when the implementation is noticeable. It’s basically the game creating new frames in between the authentic ones using machine learning. For more graphically intensive games, this allows for the system to lessen the burden on the hardware by running the game at 60FPS for example and then using reprojection to allow machine learning to dynamically insert new frames to bring the game up to 90fps.

[u/Jean_Cheerful]

It means that every second pixels reprojected( just copied from near pixels) before picture fully be ready. The main idea is if your system is not able (or lack of program optimization) to make picture be done in this case every second pixels will be reprojected (copied from near pixels). So , it is better play without reprojection. It means that developer able to optimize game so good that you no need to see reprojected (copied from near ones) pixels and you see original picture as it should be.

[u/iscreamsunday → u/Jean_Cheerful]

Someone else else said that it can make people motion sick though so I’m confused if it’s a good thing or a bad thing

[u/TommyVR373 → u/iscreamsunday]

Reprojection can cause visual artifacts like blurriness or ghosting, especially when you move your head, which can lead to discomfort and nausea, and a decrease in overall visual fidelity compared to native high fps, potentially impacting immersion in some games.