[Replied]The "moving world" issue, now i finally understand it!

Pimax 8K Series
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There’s been numerous of posts regarding the geometry distortion issue (I guess?) where some ppl see the VR world moving a bit while panning your view from side to side. This has been noticeable by looking at the SteamVR dashboard and looking left-right-left and so on. MRTV Sebastian @mixedrealityTV was one of the first ones mentioning this.

Now personally I have never seen this issue until yesterday, despite really looking for it. What made me to finally see the distortion was the fact I tried to use the original Vive 18mm face pad and on top of that, the 6mm VR cover face pad with pimax 5K+.

I did this just for science to see how much FOV you lose by increasing the distance between the lenses and your eyes.

What I immediately noticed though, was this strange effect of things/objects/walls moving when I moved my head. A very weird and distracting feeling. And yes, it was very noticeable in the SteamVR Dashboard.

Switching back to only Vive 18mm face pad removed the problem completely. Same when moving back to original Pimax face pad.

Now this got me thinking. I know all people have different face shapes and the depth of your eyeball position can differ a lot.

Try this:
If you have a problem with the “moving world” issue, could you please test using a thinner face pad than the original Pimax, to see if it solves the problem for you? Or maybe the other way as well, try a thicker face pad?

I think the distance between your eyes and the lenses is crucial, and needs to be correct to really get the proper view. Note that in both cases, the image was 100% sharp, so the distance does not increase/decrease optical quality.

Suggestion to Pimax team:
I think the Pimax team should elaborate with the removable plastic part (between the headset and face pads) and maybe make 3 different models, one original, one a few millimeters thinner giving a smaller distance between lenses and eyes (to solve this issue), and a third model with bigger distance, made for people with glasses. The plastic part is easy to remove and put pack, and I think making variations of this part could be a more sustainable way instead of creating lots of different face pads.

Let me know what you think!

@anon74848233 @PimaxVR @deletedpimaxrep1

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Can’t you simply press down and pull back the headset a bit to see if any position solves the issue? Much like the repositioning of the headset to higher on the face for some people

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Yes i saw the issue as well by slightly pulling back the headset, but its difficult to hold it in place like that.

Pressing the headset against your head might help just to see the difference.

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What part of image where you can see this issue?

Interesting if we can understand about this effect and may I will return to get 8k instead.

Do you already test revive latest version? I can’t describe the effect easily, the image have the correct proportion, but when turn around, the image is looking has smoothness of movement, but not relate the head. It look like easing movement or have some distortion which be difficult to notice. May I try it again tomorrow.

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Is this the same as the “wobble” effect that Sebastian pointed at some time ago in the 8k?

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Hmm if you are talking latency, I tried before with even no facepad and was worse maybe because my hands were holding it and it was shaking more, I tried thick facepad, and thinner old gearvr one, and still saw the wobbles unfortunately.

Good you can see something now though! Though its not really any sort of geometric distortion I see really, this might be a different issue you are describing with the lenses at a distance? The 8k latency some see is just straight up delay compared to 5k+. Here is another test that may work for you:

@SweViver @mixedrealityTV Possible latency test to try: When in steamvr home put your left eye where right eye is supposed to be (Yes this sounds weird but hear me out! lol) hold the virtual vive controller up on front of you and stare at it. And make your right eye look at the real vive controller in real life, left eye virtual one. The two should converge into one controller.

Now that the virtual one and real one line up perfectly, wave the controller around and see if your left eye lags behind the real controller on right eye. I did this yesterday only on the 5k+ so far and it was a perfect match. I could count maybe one or two pixels delay. Haven’t tried 8k quite yet.

Edit: You shoud also wobble the hmd when doing this test and see if the virtual controller wobbles compared to real life one! On 5k+ it basically holds perfectly in place like real life controller in right eye.

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It would be awesome if someone would write a kind of calibration guide for newbies.
Or make a video… :thinking::smirk::wink:

Edit. Or even make a calibration helper app to go with pitool… or does it exist already? @Sean.Huang

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When I use the headset first time I can see some image moving at the left and right side closed to the center, not geometry distortion but look like looking image behide the glasses or some magnifier. There are a lot of effect when turn around. So want to know more detail.

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Nope. This is not the wobble effect i think. Its kind of a “wrong perception” issue. When u move your head to the right, the object in front of you moves slightly with your head movement, and it almost feels like its rotating towards the side with your head movement. It feels like the percepion or point of view/FOV is larger than its supposed to be from that angle.

It’s most noticeable on big objects/menus in the central area of the view. This has nothing to do with the peripheral view edge distortions.

Yes maybe thats what the same thing i saw when trying Luckys Tale without using Lighthouses the other day (see my post about it). I assumed this was some kind of input delay/lag caused by using internal tracking only, but im not 100% sure we are talking about the same issue. But yes it was with latest Revive.

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Thats EXACTLY what I mean. I can only see this when i increase the distance to the lenses, as mentioned above.

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I see this effect when test by fruit ninja, but after that I don’t found too much. I have though that I am familiar with this effect or good rendering in some game. I will test again tomorrow.

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No this is not about latency, and i have so far only tested this on 5K+ only.
I think ita basically a wrong perception issue, creating a very slight effect of things not being static while moving your head, but moving/turning a little bit with your horizontal head movements. I did not see this happen when looking up/down.

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Oh okay yes it seems this is a different issue.

@SweViver If you get a chance definitely try that sort of “mixed reality” vive controller latency test I described above (if you can) I feel you might be able to see the latency differences between the two headsets with this finally as it makes things much more obvious.

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Distortion is different effect, if you use large fov, when you turn left and look at the right edge. You will see image is compressd at the edge. I think it should be stretching instead.

This is easily to see in steamvr home.
Once time I found wrong edge rendering too, but not found after restart Pitool.

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I will give it a go this weekend. Working my last night shift and didnt bring anything more to work than my laptop and the headset :slight_smile:

Yes this is a completely different thing. I guess its caused by the flat part of the lens edges. They may need more software distortion profile adjustments to fix this…if even possible :thinking:

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The images we look at through the lenses are projections of the game world onto flat planes. Our eyes need to be in a position, relative to the screen and lens, that corresponds to the one between the game camera and view plane - otherwise the projection is off.

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Exactly, the projection will be slightly “off”! But I never expected this becoming a problem just by adding a few millimeters of thicker face pads.

I remember @anon74848233 mentioned they have been using different thickness of the early face pads and also sent out face pads to early backers with slightly thicker face pads. Maybe this is why some backers see this problem while most of them dont.

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With the scale between virtual world, and the size of the HMD, and the effects of the lens, a few millimetres on the viewer side of the lens quickly becomes metres in perceived view. :7

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I agree, except for maybe. I think this is 100% related to face shape and pad width.

@Sean.Huang: I’m a software engineer; I would suggest that you investigate changing the eye position in the “lens-matched shader” calculations. That is, could you please provide a range of distortion profiles, based on eye-positions? This would fix some major user complaints.

Also, I recommend this as a per-eye adjustment. This would improve the user experience for people who have different IPDs per-eye (center of nose to pupil distance varies from left to right eye). At least 1 backer has serious usability issues regarding this.

Something to consider: If you can provide enough info as to how to construct valid profiles and hopefully provide an API that allows for dynamic update (can change it without restarting any app), I’m sure someone in the open source community will come up with modified profiles.

There’s also potential for using this for dynamic distortion adjustment based on where the user is looking (which slightly changes the pupil position). Ideally, there would be a few grid profiles, with some way to interpolate a continuous set of distortions.

These profiles would NOT have to be delivered all at once and could later be modified or expanded (adding more eye positions). As an aside, please add brightness and color settings first. Those are more important, imo.

@Sean.Huang, If you have any questions, please don’t hesitate to PM me.

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Just making a note here… (uncertain success): The Rift DK1 settings window had you enter how much eye relief you were using (only it asked how many notches you had it telescoped, without any regard for how your face shape affects things), and there is already an “eye relief” parameter, in the configuration sets that sjef dug out of pimax’s binaries. :7

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