Lack of G-Sync on Oculus Rift

[Blue_Ninja0]

Hello
I'm new on this forum, but an old reader of the site and a big supporter of the improvement of the perceived smoothness on videogames and other imagery.

I am really excited about G-Sync and the only reason I still haven't got it is because I'm waiting for an IPS or VA panel that supports it.

Another technology I'm really excited about is the Oculus Rift, but a thought has been troubling me and you probably guessed it: There is no variable framerate support on it, as far as I know. And I think that's even worse than not having that support on monitors.

From my understanding we'll have 2 options:
-Vsync off and suffer the screen tearing, which is distracting and will degrade the sense of immersion;
-Vsync on and suffer the input lag that comes associated with it, which has an even worse effect on a virtual reality headset than it has on a monitor, because it will add latency to your head movement and cause nausea, and also breaking the sense of immersion;

John Carmack and others have been stressing how important low latency is for a virtual reality environment, to improve immersion and reduce nausea as much as possible. Not to mention stutter, which might be present in both Vsync scenarios.

Am I wrong in these assumptions? I haven't tried the Oculus Rift yet, but I have seen raving reviews, which is great. But still this point worries me.
Anyone who has tried the Oculus wants to give their 2 cents and ease my mind?

[RealNC]

The raving "reviews" are probably the result of demoing using non-demanding 3D graphics and very fast PCs. If you get 300FPS, vsync doesn't matter much anymore. Tearing is virtually non-existent (it's still there, but it's very difficult to see it.)

But for the final end-users, with non-monster PCs and more demanding games, this will be a much bigger problem.

Although it might be quite a challenge to fit a gsync module in there; if the DIY gsync kit is anything to go by, it definitely can't go into the headset itself.

[Blue_Ninja0]

That is a good point. But that worries me.

Couldn't it be possible to have an external G-Sync module that then has a cable that goes into Oculus? Instead of receiving the HDMI connection directly.

If in the end we have to make do with fixed framerate, then I guess the only solution is to really have beastly PCs to generate huge amounts of fps.

[Chief Blur Buster]

I think eliminating motion blur first is far more important for VR.
GSYNC will be very useful for VR.
But GSYNC doesn't have low persistence yet.

Turning your head during VR creates smooth panning, which creates massive motion blur that requires nearly quad digit refresh rates OR strobing to achieve low persistence such as 2ms. Ideally, combining low persistence (requires strobing to pull off 2ms. As you can't do strobing and GSYNC yet, then strobing is preferred for reducing VR nausea if you had to choose between GSYNC versus low blur. Note that 2ms persistence is totally different from 2ms GTG transition response. Doing 2ms true frame persistence without strobing requires 500fps@500Hz which is impractical today). Eliminating motion blur first, as they are doing in the new DK2, is the wise move first, IMHO.

The below is a huge issue with VR.
View the below on a non-strobed LCD, look at the first UFO then Look at the second UFO.

(Can click for bigger version)

Low persistence solves this blur issue. Fast movement versus stationary looks clearer.
It makes VR more pleasant.
For technology or human vision explanations, see the Area 51 forum

Eventually, GSYNC could be combined with strobing, for the best of both worlds.

[RealNC]

View the below on a non-strobed LCD, look at the first UFO then Look at the second UFO.

Btw, I'm wondering, what do you see on a CRT or strobed LCD? On my 60Hz LCD (obviously non-strobed), looking at the top UFO results in me seeing vertical bars. They are perfectly stable and stationary for the duration of each cycle (for as long as I can fixate my eyes perfectly without moving them; if my eyes move slightly, or when I move closer to the screen, the bars flicker a tiny bit) with black spaces between them and they move a few pixels to the right after each cycle. Looking at the bottom UFO, I see a scrolling checkerboard pattern.

What do you see on a strobed LCD?

[Arbaal]

Btw, I'm wondering, what do you see on a CRT or strobed LCD? On my 60Hz LCD (obviously non-strobed), looking at the top UFO results in me seeing vertical bars. They are perfectly stable and stationary for the duration of each cycle (for as long as I can fixate my eyes perfectly without moving them; if my eyes move slightly, or when I move closer to the screen, the bars flicker a tiny bit) with black spaces between them and they move a few pixels to the right after each cycle. Looking at the bottom UFO, I see a scrolling checkerboard pattern.

What do you see on a strobed LCD?

The bars and patterns are not the important aspect of that test. If you look at the bottom UFO, you should see it blured. On a strobing LCD/OLED or a CRT you will see it crystal clear without any bluring (or at least with much much less blur). In VR that blur is very distracting and breaks the feeling of "presence".

[Blue_Ninja0]

I think eliminating motion blur first is far more important for VR.
GSYNC will be very useful for VR.
But GSYNC doesn't have low persistence yet.

Eventually, GSYNC could be combined with strobing, for the best of both worlds.

Yes, I agree that eliminating motion blur is more important for VR, and I imagined they couldn't even consider variable frame-rate because there is still no way to do adaptive strobing (though I hope they adapt G-Sync to sooner or later use the technique, as it is at least mathematically possible, as described on your article).

But I still worry about the screen tearing problem. I am very sensitive to it when playing on my 60Hz monitor. Do higher Hz significantly reduce the artifact? I was very happy to know that Oculus Rift DK2 has an upped 75Hz refresh rate, and the final consumer version has been alluded to have even higher refresh rates, so I'm hoping that will reduce the screen tearing problem a bit. At the same time I've heard that the reduced motion blur of strobing accentuates the visibility of the artifact.

[Chief Blur Buster]

But I still worry about the screen tearing problem. I am very sensitive to it when playing on my 60Hz monitor. Do higher Hz significantly reduce the artifact? I was very happy to know that Oculus Rift DK2 has an upped 75Hz refresh rate

As you know, VSYNC ON rather than VSYNC OFF would be the soution to tearing. The problem, that you know, is the input lag that this adds. However, if DK2 is multisync (can sync to any refresh rate), then I would imagine that doing a frame cap slightly below the refresh rate, in source engine games, (e.g. fps_max 74) actually eliminates most of the VSYNC ON latency by preventing buffers from piling up, though not as good as GSYNC.
EDIT: Correction; a display doesn't need to be multisync. Just run at fixed 75Hz then use a frame cap slightly below, e.g. 74fps, to prevent framebuffers from piling up during VSYNC ON. A number of CS:GO players using VSYNC ON (due to hating tearing) say they see significantly reduced VSYNC ON input lag when doing an fps_max 1fps below their fixed Hz. I should do high-speed-camera input lag tests of that sometime!

[Blue_Ninja0]

As you know, VSYNC ON rather than VSYNC OFF would be the soution to tearing. The problem, that you know, is the input lag that this adds. However, if DK2 is multisync (can sync to any refresh rate), then I would imagine that doing a frame cap slightly below the refresh rate, in source engine games, (e.g. fps_max 74) actually eliminates most of the VSYNC ON latency by preventing buffers from piling up, though not as good as GSYNC.

Why does DK2 have to be multisync for us to be able the use the "trick" you described? Can't we do that at specifically 75Hz? Or did you mean setting the max fps and Hz at slightly below the FPS I'm expected to get from a certain game so that the VSYNC buffer doesn't pile up?

And if that is so, wouldn't that be the holy grail for eliminating all the screen tearing and input lag problems on all games without the need for G-SYNC? I'm sure I'm missing something.

And that is disregarding the fact that there are huge fps variation in most games.

[RealNC]

And if that is so, wouldn't that be the holy grail for eliminating all the screen tearing and input lag problems on all games without the need for G-SYNC? I'm sure I'm missing something.

The downside is that you get frame skipping. Which is why I never use that method. You can test it yourself. Start a game that uses the Source engine (any Counter-Strike will do), enable v-sync, and type "fpx_max 59" in the console. The game will stutter exactly once per second.