Shabi's Vive vs CV1 comparison, with ATW info.

[Shabi]

TLDR: if you just want to play DCS get the CV1.

 

After buying the Vive and using it for about 3 months now, my friend who has a Vive and CV1 needed to do some dev work with two Vives. We did a swap a few days ago and I can now directly compare the two as it relates to DCS. I'm not a developer for real-time rendering but I do work professionally in the pre-rendered CG discipline so I can offer a somewhat valid point of view.

 

On this message board thanks in large to Skatezilla's posts we know that there are severe FPS limitations in DCS due to the DirectX API and the number of draw calls needed to render so many trees, buildings etc. I rarely render at 90fps in VR with this system (I only get 90fps if looking straight up).

 

i7 4790k @ stock, gtx980 stock, DDR3 2400 (PC3 19200).

 

With these settings for the Vive and at a render resolution multiplier of 1.5x I get the lower reprojection lockoff of 45fps most times, often dropping to 35 or so with the instant action, f15c intercept mission:

When the bombs hit it drops to about 12fps, judder is extreme, and @ 30fps very uncomfortable forcing me to limit how fast I turn my head.

 

Switching the Vive for the CV1 and setting pixel density to 1.5x gives the same FPS, which isn't really that surprising since it's rendering the same thing at the same res. However there is one thing that means I can jack the render settings up, and that is Asynchronous Time Warp. I could now set Shadows to HIGH and pixel density/resolution oversampling to 2 to achieve 30fps for a consistent minimum.

 

Similar to Vive's reprojection (but better), ATW works like this:

 

You can skip a lot of the ATW stuff if you want, but for reasons of clarity and disclosure I went through it anyway:

 

Orientation-only ATW can be used to help address judder: if the rendered game frame is not submitted before vsync, timewarp can interrupt and generate the image instead, by warping the last frame to reflect the head motion since the last frame was rendered. Although this new image will not be exactly correct, it will have been adjusted for head rotation, so displaying it will reduce judder as compared to displaying the original frame again, which is what would have happened without ATW.

https://developer.oculus.com/blog/asynchronous-timewarp-examined/

 

By "warping the last frame" they mean taking the last frame, reading the new head position & rotation and warping the old frame to kind of leave it behind. If you just displayed the last frame you'll get frozen frames, ie judder, and that's the big issue with the current Vive reprojection implimentation. For whatever reason, the oculus display driver is better at doing this; it successfully takes the last rendered frame, warps it (a very cheap CG operation) and displays it if the current rendered frame isn't ready yet, avoiding a dropped frame.

 

The SIMPLEST kind of ATW interrupt and warp is for a rotational head movement. Think about it, if the head is rotating and the position is not changing then you can just warp the image and not worry about a change in parallax (objects moving relative to each other in a frame based on the rules of perspective).

 

Effective rotational ATW is the #1 thing you want in a cockpit/seated experience because you're usually just rotating your head.

 

Artifacts: But because it's warping the last frame and you turned your head, at the edges of the display you'll see a black area where it doesn't have pixels, since you are looking in a new direction now. This becomes more noticeable the lower the FPS.

 

But what about positional ATW?

 

Well, you'll see this if you fly at 400kn @ 300ft and look out the side of the cockpit. Look at the trees, the buildings, notice the ghosting?

 

When you move your head, only the additional rotational component is reflected in the ATW-generated images, while any translational head movement since the frame was rendered is ignored. This means that as you move your head from side to side, or even just rotate your head which translates your eyes, you will see multiple-image judder on objects that are close to you. The effect is very noticeable in spaces with near field objects, such as the submarine screenshot below.

 

This is where my understanding of it becomes a bit fuzzy. It seems to be doing a mutliple frame blend of previous images, but this isn't specified in the document/blog post. More reading is required, but it should be intuitive that positional ATW is harder to do, as it means you need to take into account more than just a twisting of your vision in a static environment, instead near objects are moving past fast, far objects are moving past slowly, and don't even get started on transparency and reflections, we're not doing a deep composite in nuke using a few gigs of data per frame!

 

Thankfully, most of your attention is directed forward, not sideways, and if sideways it's to check situational awareness, not to articulate avionics and flight dynamics.

 

Why is the CV1's implementation so much better than the vives? I'm not sure, but more time, a few billion FB dollars and John Carmack might have something to do with it!

 

On to the other notes:

 

1- ERGONOMICS MATTER

More than you think. A floppy elastic head strap and chunky cable plus heavier HMD is a pain in the ass compared to a much more rigid well designed and minimal headset. It really helps your experience and makes you last longer. Sounds like a condom commercial but it's true. I expect this to be resolved in time, but it raises some worrying flags over the current state of OSVR, even if they have higher res headsets coming.

 

2- OCULUS FOV ZOOM UI LAYER THING

So far Eagle Dynamics only implemented this for the Oculus SDK, which will change. Its nice, I thought it would solve my resolution issues, but I consider it aesthetic unless you are doing an A10-C attack run. In which case it's ****ing awesome.

 

3- HEADPHONES

I like having integrated headphones that aren't a dangling cord. Yes sometimes background noise leaks in, but come on it's a jet engine, it's not an FPS. Less things to arrange on my head makes it easier.

 

4- TRACKING

Is better in the Vive, period. I don't know how Oculus will pull off room scale, my VR dev friend borrowing the headsets intimated this. It could be the reason the hand controllers are delayed so long... I get some tracking judder with CV1, although I do sometimes get dropouts with the Vive light station when doing seated VR (see following photo). At one point I had it dangling on a selfie stick which was definitely not stable enough, the fan airflow was pushing it around! (I live in the tropics and the mancave is exposed to the elements). Compared to the benefits of prompt ATW its not a big deal really, every now and again I hit numpad 5 to reset the view if it drifts.

 

5- OPTICS & FOV

About the same optics quality, but with more godrays. I don't notice it if flying during daytime, for night flights maybe the moon would be irritating. FOV is less, but I welcome that right now as I want more pixels per degree of vision in the frustum.

 

SUMMARY

With the CV1 I can render @ 30fps and move my head around in a way that doesn't feel sluggish and juddery. Given the constraints of Directx10 (is it 10, or 11, I forget?) draw call APIs we can't push that far with FPS. Since Oculus ATW is better than Vive reprojection it means I can fly with shadows turned on, and a higher pixel density/resolution oversampling. This sounds minor, but **** me it makes a difference. And hey the CV1 is cheaper, even if you are subject to a closed platform (for now). But if you want roomscale VR for parties or showing people the future of VR, get the Vive, you can still fly.

 

DX12 can't come soon enough to DCS. And OSVR reprojection improvements would be most, most, most bloody welcome.

 

Render on. Special thanks to the test pilot crew:

 

Edited July 17, 2016 by Shabi

[Shabi]

Ah man, a new DCS version came out right as I posted this. Reserving this post to note down any VR changes.

[hansangb]

Thanks Shabi. I posted a "why I chose Rift" a while back and it's pretty much spot on. Simple things like chunkier cable goes a long way when you use it quite often. Thanks for the feedback.

[Shabi]

Yep, the performance of ATW makes all the difference. It seems like this is something that all the players will catch up on, but for now it's obvious where the advantage is.

[Vivoune]

Good summary Shabi thank you for that. Personally I found the Vive to be comfy enough, I found it as comfortable as the OR rigid system, but quite harder to set up correctly, you do have to mess with the straps and cable tension a bit that's for sure. Then again everyone's anatomy is unique.

 

Personally I had no issues with the Rift's tracking system, it was near perfect for a seated experience. Do you have any sort of IR light pollution that might interfere in the background?

 

In terms of optics, didn't you notice a difference in image brightness, contrasts and colorimetry? I found that was the main reason I chose to stick with the Vive as I felt things looked a tad less crisp but felt more natural and real in comparison to looking at the world through light sunglasses through the Rift.

 

ATW sure is the Rift's strongest selling point currently, I hope something as good comes to the Vive soon enough.

[Shabi]

RE tracking, I think it might be an unstable mount, I could be bumping or shaking it. At any rate the dropouts don't happen much so it's not a big issue. In other news, today they announced that multicamera tracking is now supported, so it's a move to the Oculus Touch controllers being fully supported.

 

As far as colours and optics go I didn't notice too much other than a narrower FOV and more evident godrays. The brightness could well be lower but I had forgotten that some people found that to be an issue, so in my opinion it must be very minor.

 

What I want, what we all want, is the same thing but with a higher res screen!

[Vivoune]

Odd, I found the difference to be a game changer. That shows how everyone has a very different and unique experience and how there's only one good advice, try both before you buy.

 

Anyway, there's a 2300£ Infinitus Prime TVR Headset if you want, that's a 140° fov with 20k resolution display. :P But yeah, back to the reality, here's to the second generations arriving sooner than later.

Edited July 17, 2016 by Vivoune

[yellow_jacket]

Where is the submarine shot from? Something you're working on?

[lobo]

Where is the submarine shot from? Something you're working on?

 

Oculus Dream Deck Sub demo

[Shabi]

it's lifted from their blog post about ATW:

https://developer.oculus.com/blog/asynchronous-timewarp-examined/

 

Oh man... don't tempt me with mentions of 2300 quid headsets. I'm already ordering a rift.