Rift Judder and FPS discussion thread.

[Darth Sidious]

120 hrtz

I find that 120 fps statement too much of a coincidence as the note 3 display in our rift is exactly that.
also the 75 fps jabber sinks a bit into nonsense here and there. 75 fps is there to let the low persitance work (meaning the replacement of 50% of the frames by a black image) so we do actually see 37.5 frames.
vsinc often get stuck at this rate 37.5 as is loses the low persitance function when it dips below 75 fps.
So technically wise the software could render only half of what we think it needs.
...I dont think this software is currently implemented anywhere consumer reachable....I wish frontier gets this..

 

[saviornt]

I find that 120 fps statement too much of a coincidence as the note 3 display in our rift is exactly that.
also the 75 fps jabber sinks a bit into nonsense here and there. 75 fps is there to let the low persitance work (meaning the replacement of 50% of the frames by a black image) so we do actually see 37.5 frames.
vsinc often get stuck at this rate 37.5 as is loses the low persitance function when it dips below 75 fps.
So technically wise the software could render only half of what we think it needs.
...I dont think this software is currently implemented anywhere consumer reachable....I wish frontier gets this..

This is very dis-informative, and not at all how low persistence works. I'll explain it when I wake up, but for now, I'll leave you with a couple of videos that you need to watch:

eVRyday explains Low Persistence
John Carmack on GearVR and Low Persistence

But it did answer a question that some have posed, ‘Why does Oculus insist on 75Hz for DK2 low persistence when Gear VR runs at 60Hz?’ There’s the answer—at 60Hz and with low persistence, the screen is black for most of the duration of a frame; in order to prevent users from noticing those blanks you need to display more frames per second (i.e.: a higher refresh rate).

 

[KING5TON]

So I have a question regarding the fps.

What effect would there be if the FPS drops quickly from 120 to 75?
One assumes if the improvements are perceptible from 75 to 120 then the degradation that comes with a drop in FPS must also be perceptible even if the FPS does not drop below 75?

So is the OR FPS locked or does it go up and down as with a monitor?
Is there a way to lock the FPS also?

Nothing.
What matters is the refresh rate of the screen.
If you have a 75hz screen then any FPS above 75fps is basically wasted.
You would see no real difference between a game running at a constant 75fps on a 75hz screen and 1000fps on a 75hz screen. The screen can only refresh at 75hz, any frames produced between the refresh rate are basically discarded.

You cannot really lock the framerate. You can use Vsync to sync the max frame rate with the monitors refresh rate but that only works for the maximum frame rate. If your frame rate drops below the refresh rate then you will get issues (i.e. You can cap the maximum frame rate but you can't get it to never go below X fps).
The only thing you can do regards this is ensuring that the game never drops below 75fps at any time (e.g. your maximum FPS is 130 and the minimum is 100, with Vsync on you will never drop below 75fps as your minimum fps is way over 75fps). With Vsync on this would effectively lock your frame rate at 75fps. That's nearly impossible to do at the minute even with the top end hardware as certain circumstances cause even the most powerful PC to drop below 75fps.

 

[Mucka]

Nothing.
What matters is the refresh rate of the screen.
If you have a 75hz screen then any FPS above 75fps is basically wasted.
You would see no real difference between a game running at a constant 75fps on a 75hz screen and 1000fps on a 75hz screen. The screen can only refresh at 75hz, any frames produced between the refresh rate are basically discarded.

You cannot really lock the framerate. You can use Vsync to sync the max frame rate with the monitors refresh rate but that only works for the maximum frame rate. If your frame rate drops below the refresh rate then you will get issues (i.e. You can cap the maximum frame rate but you can't get it to never go below X fps).
The only thing you can do regards this is ensuring that the game never drops below 75fps at any time (e.g. your maximum FPS is 130 and the minimum is 100, with Vsync on you will never drop below 75fps as your minimum fps is way over 75fps). With Vsync on this would effectively lock your frame rate at 75fps. That's nearly impossible to do at the minute even with the top end hardware as certain circumstances cause even the most powerful PC to drop below 75fps.

Very informative thank you but I am unsure if the fps is locked to the monitor or the OR?
What if I have 144 mhz monitor and my FP fluctuates between 75 and 140?
Would you have to lower the monitor to 75 mhz?

 

[KING5TON]

Very informative thank you but I am unsure if the fps is locked to the monitor or the OR?
What if I have 144 mhz monitor and my FP fluctuates between 75 and 140?
Would you have to lower the monitor to 75 mhz?

If you turn on Vsync (which OVR recommend) then it could be limited by the lowest connected display (I think). I know that when I use my rift I set my monitor to 75hz by lowering the resolution to 1280x1024 (normally 1440p/60hz) so that my monitor and my rift are both running at 75hz. You can set your monitor to one frequency and your DK2 to a completely different frequency. That's allowed but Vsync messes it up and caps your FPS to the Hz of the slowest display)

If you have a 144hz monitor and you aren't hitting 144hz then I'd look to see if there was a lightboost feature and turning it on and trying it. It reduces your Hz to 120hz but improves motion blur.
Other than that then I personally would just run stuff on the monitor with vsync off and taking the fluctuations on chin and when using the rift to turn vsync on which will lock the FPS to 75fps max.

Nah, leave your monitor at 144hz. If your monitor's Hz is higher than the rift then the monitor's FPS shouldn't be limiting the Rift. Most people have 60hz monitors so the Rift can be limited to 60fps with Vsync on.

 

[Mucka]

Interesting.
How does turning Vsync off affect the FPS and quality of image on the Rift?
I can imagine getting a decent performance boost but how does it affect quality?

 

[the_wretched]

Does this imply that to get the best image with the rift we should be telling the game to render at 2364x1461? (at 75hz) or is the 1980x1080 resolution enough?

No that is only the internal rendering target size of the engine and is handled automatically for you. Some games, like some UE4 titles or Elite Dangerous offer the option to change this setting. Lowering it will lower the visual quality, turning it up is basically the same as adding more SSAA, creating a more detailed and less aliased image. Unfortunatelly ED only lets you lower this setting.

 

[saviornt]

I tried to come up with my own explanation for low persistence and how visual persistence works, however, I can't think atm. Just watch the videos and if you have any questions, Google it.

 

[Spectre Alpha]

There is no reason to have FPS over the refresh rate of your monitor, and at 1080 that is most likely going to be 60 hz or 60 frames a second displayed. At 4k you will likely have only 30 hz. on most monitors. There are some monitors that will go as high as 120hz but they are not the every day monitors most people have and if you bought one of those you most likely have 1 or 2 of the top of the line gpu's also.

Don't worry about 'needing' a 75fps card, and besides when the game is optimized the recommended stats will be a lot lower anyways.

Hope this helped.

 

[KING5TON]

There is no reason to have FPS over the refresh rate of your monitor, and at 1080 that is most likely going to be 60 hz or 60 frames a second displayed. At 4k you will likely have only 30 hz. on most monitors. There are some monitors that will go as high as 120hz but they are not the every day monitors most people have and if you bought one of those you most likely have 1 or 2 of the top of the line gpu's also.

Don't worry about 'needing' a 75fps card, and besides when the game is optimized the recommended stats will be a lot lower anyways.

Hope this helped.

FPS isn't as important with monitors, it is important in VR though and everyone does indeed need 75FPS minimum to not have any judder.

 

[Darth Sidious]

I tried to come up with my own explanation for low persistence and how visual persistence works, however, I can't think atm. Just watch the videos and if you have any questions, Google it.

I was looking forward for that.
al I think to know is we need more fps as we rotate our viewpoint. If we played with a with a fixed position like watching a movie then we would only need that forward view.
now I still wonder what you consider dis-information.
The screen is 120 hrtz and the software often gets stuck at 37.5 exactly half of 75.
Those are facts .
so where am I going wrong?

 

[hurricanepilot]

The screen is 120 hrtz and the software often gets stuck at 37.5 exactly half of 75.
Those are facts .
so where am I going wrong?

Pretty sure the note 3 screen isn't 120hz for a start. I think it's 75Hz and only then because it's being overclocked by Oculus from the standard 60.

Low persistence doesn't work by showing alternate frames of colour then darkness it works by only lighting up the pixels each frame for a moment, then turning the pixels off again. it does this 75 times a second (when it's working).

The reason it's better is a function of how our brains work:

As a thought experiment, imagine you're looking left, and you have the ability to look right in about a tenth of a second. That's 7.5 frames of data that you'll be being shown on the DK2 screen while you make that 180 degree movement. If it leaves the pixels lit up all the time, as you move your view through the 180 degree arc each frame will be being shown for 24 degrees of that arc and your brain doesn't think that makes any sense. So, what low persistence mode tries to do is flash the image at you as quickly as it can so that during that 24 degrees, the pixels are only lit up for the first few degrees and then it's black until the next frame. Your brain is way happier with this as even though you aren't being shown a picture at all times, when you are shown a picture, it makes sense.

 

[Adam Lusardi]

Very well explained.
-
This is why went locked at 60Hz (playing with direct mode and tv) my rift is unplayable.

 

[Mark D]

Pretty sure the note 3 screen isn't 120hz for a start. I think it's 75Hz and only then because it's being overclocked by Oculus from the standard 60 ......

I think you are correct

"According to its spec sheet, the DK2’s display runs at 75 Hz. The Note Display, by default, runs at 60 Hz. So it seems Oculus has overclocked the screen to bump up the refresh rate a bit."

Source : http://techcrunch.com/2014/07/31/oculus-rift-dk2-gets-torn-apart-revealing-its-samsung-innards/

 

[BigDuke6ixx]

Close one eye and that's slightly more than the FOV you get with the Rift. Also put a mosquito net over your head and the a bit like the resolution. The frame rate, FOV and resolution are all good enough for me with the DK2. Foer the CV1 you'll need a fast machine.

 

[Chris Dettmar]

I think we also need to see what optimisations have been made. Let's hope there's some big improvements tomorrow!

 

[elkar]

It gonna be more like Q4 2015 for customer version.

 

[saviornt]

90 FPS at 2560x1440

 

[Adam Lusardi]

90 FPS at 2560x1440

No 90Hz...............If the buzz is correct!

 

[saviornt]

Vsync...

edit: the poster asked about framerate and resolution. The graphics card doesn't drive the frequency of the screen (hz), but it does drive the framerate (fps). You will need to pump out 90fps. Take a look at the Oculus connect conference with the guys from Epic (the mentioned that their demo had to maintain a framerate of 90fps on the CB demo)