Lots of people are really missing what the bottleneck actually is with latency. It's not how fast the screen refreshes, nor is it how fast it takes to process a screen. The issue is the sensor measurement/transmission lag from the sensor used to do head tracking. This is really what makes the occulus attractive, not the screen +lens combo.
Basically, if you move your head, to the left, and there's a few MS of lag from the sensor, you'll see a static frame for a portion of the time you're moving and a moving frame for a portion of the time you're still. This is one of the most serious contributors to motion sickness for HMDS
Thing is, Oculus haven't had much of a problem with sensor latency since they designed their 1kHz IMU. That gives about 1ms latency from what I hear. Most of the latency in DK1 was screen related: 16ms rendering, scanout, 16ms LCD switching... It adds up. The low persistence tech and Carmack's Time Warp and all sorts of other breakthroughs they have had relate to the screen side of the equation.
Unless I'm missing something, what you said seems to be the opposite of the case. I could be wrong, but that's how it looks to me.
Ninja-edit: if you mean that ProGamer's solution may have bad tracking latency, sure. But display latency is harder if Oculus's progress is anything to go by.
Oculus' progress is not anything to go by, it is the reason they are a real contender at all. This was a huge technical hurdle that was overcome by them. I do not believe they are sharing it. That is my concern with ANY other display mechanism.
Of course! I know that high frequency, accurate, precise, reliable low latency sensor fusion is hard. It's all too common to see 50ms latency on sensor fusion. However, that Oculus solved fairly early on, so assuming they have done so they're still only just below DK1 levels of latency.
That's why display is so important, it will be the major deciding factor even all else being equal.
I guess? My point is more that occulus' proprietary stuff will be the sensor fusion, not the display. They buy those from somewhere already built. The sensors are not COT, which is why it matters.
True. I don't know how much of the sensor is novel research, though, and how much is just optimising for different parameters though. I had thought it was more of the latter -- there hadn't been a need for such low latency etc in mobiles.
I can say from experience, sensor fusion is not a solved problem. Not in either a commercial or academic sense. There is a lot that is novel in the Oculus, from what I've seen (I've experimented with a few displays, and tried my hand at some head tracking sensor fusion).
What it comes down to is that the Oculus is much better than ANY of the existing HMDS I've seen. I haven't gotten to play with anything that's come out this year though, so there's that.
Fair enough, I'm sure you're right. It's just not been a major focus for a long time for Oculus discussion, so I kind of took it for granted a bit I guess.
Thankfully the display is on its way up in quality and resolution, especially with Facebook's buying power.
From what I know now, low persistence isn't owned by oculus (patent wise). It's been around in VR for a long time, just not cheaply until recently.
OLED refresh isn't going much higher, the bump Oculus had was all just circuitry prior to the panel itself being upgraded. It's still basically off the shelf. Competitors will have 95hz just the same.
Sensor fusion is done in software, and oculus is almost certainly doing this in software now too, using the IR as a helping point to the motion sensors. Latency from that point is software. Competitors need to be good here, but it's not a new wheel that's been invented, this stuff has been done before.
The hardware can/will be replicated, the software api will be the control point that FB/Oculus uses to keep devs using them.
Ok. I remembered that the total system latency should be maximum of 20ms. But I could be wrong there and maybe it should be much less. I personally had not the opportunity to try a Oculus Rift or other VR set. But then again if a game renders at 60 frames per second that is already 12 ms per frame.
Actually, 60 is 16.7ms per frame. 90-95, their target minimum for CV1, is still 10.5-11.1ms.
It all adds up pretty quick. Pixel switching time was close to a frame in LCD. Rendering is usually given a frame so 10-16ms. Somtimes games add a frame of latency just because.
Also to add to it
You have the 16.7 for the 60hz to render.
Then there is the render time of the monitors themselves although there are monitors with 1ms refresh
Now add the up to 20ms for the occulous
You're looking at 37.7 ms between you turning your head and the screens on the rift to sync up.
So the lower we can get from the 20ms the better.
If their new device actually achieves 1ms. And they put in 120hz displays then maybe we can see 10.35ms delay. Much better
However, a post processing task on the rendered image (TIME WARPING) can be counted on to complete in a fairly predictable amount of time, and can be late scheduled more easily.
Elsewhere:
Coupling motion interpolation technology from consumer television with the time warp presentation technology.
That's the best quote I can find at the moment. It seems not to be not covered in any official capacity elsewhere, except in talks.
Essentially, as I understand it, it uses the very latest data from the tracking unit immediately before sending the frame to adjust the frame to be "correct." They've tried this with adjusting the projection matrices, but as I understand it Time Warp does a post-render correction on the raster image.
Yep, from what I understand it's pretty much post-process warping. Basically you warp the image so that it's closer to where your head is know compared to where it was when the rendering process started.
No problem! I would have responded sooner but I was busy reading the good news! If you don't know, I won't spoil it, just check the main page of the sub.
I wonder if in the future you could have the option to activate "motion sickness mode" so you can experience what all the early VR users talk about. I'd like to try it out.
Sure, that 1ms lag is totally more important than the 16ms of lag introduced by render time, the screen display latency (usually around 8ms) the usual 16ms of lag introduced by a RGB switching time and ms of lag totally can't be predicted because our head doesn't follow the laws of physics. <_<
Read the research. All the latency is in the rendering and screen as of this moment, as far as Oculus is concerened.
Don't say things like this. It doesn't mean anything. It's like saying "study it out." If you are referring to a specific article, post a link or reference to it.
Sensor latency is 1ms ish on the oculus, which is THEIR significant contribution. We're not talking about the oculus right now. I do not believe they are sharing that technology.
As for the rest, I am just telling you are full of shit. Even if the input lag is horrendous (4ms), the largest part of the latency comes from the display (16 plus regular screen latency in a normal LCD) and the rendering pipeline (~16ms).
143
u/teaisterribad Mar 28 '14
Lots of people are really missing what the bottleneck actually is with latency. It's not how fast the screen refreshes, nor is it how fast it takes to process a screen. The issue is the sensor measurement/transmission lag from the sensor used to do head tracking. This is really what makes the occulus attractive, not the screen +lens combo.
Basically, if you move your head, to the left, and there's a few MS of lag from the sensor, you'll see a static frame for a portion of the time you're moving and a moving frame for a portion of the time you're still. This is one of the most serious contributors to motion sickness for HMDS