[DiY] HTC Vive / Pro - Mit Linsen der GearVR tauschen

Kniffo · 26. April 2018

also ganz schwarz?Hab bei Kleinanzeigen vorn schwarz hinten grau? oder weiß? gesehen...

SolKutTeR · 26. April 2018

Wie gesagt, sicher bin ich mir nicht.

2017 ↔ 2016

Kniffo · 26. April 2018

2016 soll ja auch funktionieren Nur die 2015 nicht...

SolKutTeR · 26. April 2018

Zitat von Kniffo: ↑

...Nur die 2015 nicht...
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Dann Vorsicht, die 2015ner Version war ebenfalls weiß!

2016 ↔ 2015

[Edit]
Habe das ganze mal ausgegliedert, dass Thema sollte schon einen eigenen Thread besitzen.

axacuatl · 26. April 2018

Hier mal etwas Food for Thought (aus einem Pimax Forum Beitrag kopiert):

"Just to make this 100% clear: the GearVR lens swap is by no means an 'obvious choice'. Using those lenses, even with said barrel distortion patch, overwrites the UNIQUE values that as part of the production of your HMD are being TESTED for INDIVIDUALLY. That fact already should give you a clear understanding of just how sensitive any value change is when it comes to optics. Less than 25% of all 'lens swappers' that partook in a recent r/vive survey stated they would keep the change after extended use.

Why? Because whilst those GearVR lenses do greatly increase the sweetspot and do away with godrays and other artifacts, they cause chromatic aberration and pupil swim. Users don't always notice these anomalies right from the get-go, but after a while they do over-tax our perceptory system and can lead to a feeling of unease and eye-strain.

Now unless your are calling the wizards at Valve who have been researching most of the data that current HMDs are based on idiots, anyone who takes the effort to actually try and understand a subject matter before insulting others would realize that fresnel lenses have been chosen by most HMD manufacturers because they mitigate some of the most inherents faults with traditional lense design whilst also being lightweight and pretty cheap to produce.

This is nascent tech and there will be many more compromises to come before we have 'retina' perception in an HMD.

Oculus GO lenses have been reported to be the next significant iteration of VR lense design and whilst I don't care for the HMD itself, I'm excited to have a look at them. After all, without a significant paradigm shift in VR-related optical design, eye-tracked foveated rendering becomes considerably less meaningful."

Kniffo · 27. April 2018

Ich möchte den Swap trotz einiger Zweifel im Pimax Forum und auf Reddit gern mal probieren.
Hab eine Online Druckerei gefunden aber bin mir bei der Auswahl des Materials nicht sicher.
Was sollte man nehmen?

Sind die Masse denn so auch korrekt?

SolKutTeR: Beiträge zusammengefügt

Hammerschaedel · 27. April 2018

hier mal die Statements von Alan Yates dazu...

https://twitter.com/vk2zay/status/987526618028564480

Yes each panel-lens assembly needs individual calibration for good performance. The main problem with other lens types is distortion variation over the eyebox "pupil swim" that can not be dynamically corrected without high performance eye tracking.
Klicke in dieses Feld, um es in vollständiger Größe anzuzeigen.

You should always be skeptical of everything, especially statements from allegedly authoritative sources.

This whole thread is about my reply to specific questions on twitter. Let me be clear; hacking on the Vive is something I actively encourage. I and many others at Valve were careful to keep the Vive and the Steam VR platform as open and hackable as possible, that is why we encouraged HTC to include features like the aux' USB port and chose not lock down the firmware images.

If people want to change the lenses on their HMD, go for it!

Just understand first that the frensel lenses were specifically designed to minimise some dynamic distortions that we know can cause discomfort and motion sickness. The frensel lenses were not selected for low mass, low cost, hiding subpixel structure, filling SDE or any of the other crazy conspiracy theories I have read. They were the only practical lens technology for hitting the overall set of optimisations we wanted, especially minimising eye-position dependent distortion with a single element. They are not "cheap" lenses and need special equipment to make well. They are lower mass than the "equivalent" non-frensel profile lens, but that is mostly a happy coincidence, if a conventional lens could achieve the same performance in the axes we care about we'd happily tolerate the small mass increase for the reduced stray light and easier moulding. Our goal was to have lenses that worked well for everyone, from the least sensitive to the most easily nauseated. Some people just don't perceive pupil swim, at least not until you tell them what to look for, and some people once they see it can't unsee it and it ruins all HMDs with swimmy optics forever for them. Most concerning is that swimmy HMDs cause nausea at an almost subconscious level, you don't need to perceive it for it to make your experience using the HMD unpleasant.

We also knew using frensel would mean accepting more stray light (aka "god-rays") and would make the lens much, much harder to manufacture. It is technically difficult to make frensel lenses with low stray light by injection molding, you also have to be careful about spatial frequencies and a bunch of other important details. The Vive panels are brighter than other HMDs so we actually did quite well to keep the stray light to the levels you experience in the Vive lens. This is one of the many knobs HMD makers can use to deal with the various trade-offs in the optical system; turn down the brightness, soften the contrast, adjust the lens MTF, reduce the FOV, shrink the eye-box.

There were a lot of design compromises in the Vive lens. Just whacking some magnifiers in front of a panel and calling it good will "work" to some degree, but devil is in the details if you want good performance. The entire point of a HMD is to produce stimulation of your visual system that is as close as possible to the natural light field you experience viewing the real world. At practical consumer cost points and with the technology available right now the lens is near-optimal for the panel and the objective function it was designed for.

Why do you think almost every high-end HMD since our Steam Sight prototypes were demoed uses a frensel based lens design?

Now I don't for a moment suggest there aren't better optical designs possible. We already have better ones, no doubt others working the HMD space have also caught up and likely have their own high performance designs for next generation HMDs too. I also recognise that some people care about different aspects of lens performance than others. But if you are wanting a "better" lens for your current HMD just realise there is a lot to try to optimise for at once and there is a great deal of prior art to understand before you can truly design something objectively better.

All that said; say pupil swim doesn't bother you and you are OK with the GearVR lenses, the general difficulty that you will experience substituting HMD lenses is getting the resulting display calibrated properly. Firstly the lens should have the correct focal length and be mounted at it with respect to the panel emission layer, it has to collimate the display output so you don't need to accommodate through any focus error (assuming you are young enough to still be able to accommodate fully). If you end up on the wrong side of focus it will be very hard to accommodate even with young vision. Then you need to measure the radial distortion of the lens, for each wavelength of the display light emitters and compute the distortion polynomial coefficients for each channel. Plus if you want it to be really correct you need to deal with the pose between the lens and the panel not being perfectly parallel, and the lens center not being on the central pixel of the display - which matters a lot at the edges, you actually need sub-pixel centering to do it properly. The pose of the eye tubes relative to the tracking system is important too, including orientation errors. Humans can tolerate a surprising amount of error here, because eyes don't simply pitch and yaw around in our eye sockets, they roll too and to some degree our brains can deal with angular errors and still fuse a 3D image. You eat some of the angular budget with the lens alignment errors if they aren't calibrated properly.

The calibration machine is pretty simple, a calibrated camera with the right lens, but the software and the maths to do it properly is non-trivial. Sure you can just fiddle with the coefficients until it looks right - I know some HMD manufacturers do this and some that use the same calibration for every HMD. This may be OK if they can hold tolerances or their tracking or lens MTF is so crap it doesn't matter anyway. Bodging it may work OK for insensitive individuals, but we wanted it as correct as possible so as to not eat into the margins of not-quite-correct stimulus that eventually lead to loss of presence and outright motion sickness.

There are a few other details too, like not letting dust get into the optical assembly while you are changing the lens, accepting that if you change your mind and reverse the modification process it will result in a small calibration error (probably tolerable), etc...

While we are at it, I also never said thin-foam was a bad idea. Anything that gets your eyeball closer to the lens will make things better, more FOV, less swim, better focus at the periphery, less stray light. If you can stand your eyelashes touching the lens all the better - but it doesn't leave a lot of room for avoiding it contacting your cornea if you fall over or hit the headset against something.

I do not believe in advising people to just suck it up and develop "VR legs". Firstly we don't exactly know what happens long-term if you train yourself to ignore that kind of conflicting sensory information. There is reasonable evidence that it is possible to safely develop resistance to sensory conflicts; people get used to eye-glasses and their associated distortion, riding in cars, in boats, in aircraft and space vehicles etc. However I have read some research that suggests a small percentage of simulator users never fully adjust and suffer nausea every time, it appears some people are just more hard-wired to trust some of their senses more than others.

TLDR: hack away, use what works for you.

If you want to do serious work improving the state of the art in HMD tech science is your friend. Measure the existing solutions to the problem, theorise about their short comings, design experiments to prove fixing them is important perceptually, measure your results, change what matters, etc
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https://www.reddit.com/r/Vive/comme...tes_on_the_gearvr_lens_mod/dxzkm5o/?context=6

DerDod · 27. April 2018

Ich wäre wirklich gespannt, wie sich andere VR-Brillen mit den Linsen der Go machen würden. Ach was, eigentlich hätte ich gerne eine Oculus Rift lite für sagen wir 199 Euro mit dem Display und den Linsen der Go. Da lebe ich auch mit dem schlechteren Schwarz vom LCD und den nur 72 Hz.

axacuatl · 27. April 2018

Zitat von DerDod: ↑

Ich wäre wirklich gespannt, wie sich andere VR-Brillen mit den Linsen der Go machen würden. Ach was, eigentlich hätte ich gerne eine Oculus Rift lite für sagen wir 199 Euro mit dem Display und den Linsen der Go. Da lebe ich auch mit dem schlechteren Schwarz vom LCD und den nur 72 Hz.
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Was ist denn jetzt schon bekannt über deren Linsen - las auch dass die angeblich die Next Gen Linsen sein sollen, aber wie & was hat sich mir noch nicht erschlossen...

DerDod · 27. April 2018

Ich darf leider erst zum Release der Go mehr darüber verraten. Aber der erste (längere) Eindruck ist sehr sehr gut.

[DiY] HTC Vive / Pro - Mit Linsen der GearVR tauschen

Kniffo

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SolKutTeR

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VRF Team

Kniffo

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SolKutTeR

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VRF Team

axacuatl

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Kniffo

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Anhänge:

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Hammerschaedel

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DerDod

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axacuatl

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[DiY] HTC Vive / Pro - Mit Linsen der GearVR tauschen

Kniffo Forenaktivist

SolKutTeR ADMIN VRF Team

Kniffo Forenaktivist

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axacuatl Forengott

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