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karrtoon
Up and Coming
May 17, 2016

lens distortion on my app in CV1 (also notice on other apps now too)

I have a mountain scene in UE4 I have been working on with the Vive and DK2 for the last month. I just got the CV1 today and the first thing I noticed is when I look around the scene, especially all the way up then all the way down at a cliff (or distance view) the CV1 has very noticeable warping. I do not wear glasses, have 20/20 vision, and my eyes are close to the lenses.. but it doesn't seem there is a way to adjust the eye relief to keep the lenses further out to elimimate this edge warping of the geometry. It almost reminds me of Vorpx if you have the software fov setting too high.

A good test for this is the rooftop demo. If you look far left and far right in the rift back and forth while staring at the buildings there is some subtle lens distortion and stretching going on. Where as if you run the same demo with the "revive" hack and check the demo on the vive the lens distortion is near perfect. (It is also perfect when I check the DK2)

This is making me think whoever set the unwarping of the image for the CV1 lenses did not eyeball it properly (no pun), or perhaps they didn't set these distortion parameters as well as they could have been set. The image seems to not be precisely warping with the CV1 lenses' curvature at the enges and feels very subtly off when compared to the Vive and DK2. I am posting this in hopes that whomever is in charge of this aspect at Oculus takes notice and can hopefully get it resolved.

4 replies

karrtoonAuthor
Up and Coming
May 18, 2016
Thanks, Have a nice day.
Mace404
Inspiring
May 18, 2016
Try tilting the CV1. Good chance the bottom of the unit is too far towards you (so tilt the bottom away from you)
If it gets unclear move the unit a bit higher on your face
Also make sure the headrest is far enough so it gives enough support.
You can let the CV1 'hover' in front of you and just rest on the top part. It doesn't need to touch your cheekbones.(or just lightly)

This solved the little warping for me.
karrtoonAuthor
Up and Coming
May 18, 2016
Thanks for the idea, unfortunately it was a no-go. I actually just got a message from Doc_ok on reddit and it seems like it's probably an issue with the CV1 not having eye relief and me not in the "optimal range" with my face type/eye position, here is the comment:

"My best guess is that
you're seeing a physical/virtual FoV mismatch. If your eyes are closer
to the screen than what the software considers "normal," you are seeing a
smaller FoV because the lenses magnify the screen image slightly less.
You can see the magnification difference in the images in my FoV
article: in Figure 29 (5mm eye relief), the lower-right corner of the
screen is 50° from the center; in Figure 30 (10mm eye relief), it's 55°
from the center.


If the software uses the same rendering FoV in both cases (and since
it doesn't know your actual eye relief, how could it not?), you'll get a
mismatch. The symptoms of FoV mismatch are exactly what you describe:
the world warps as you rotate your head while fixing your eyes on a
fixed point in the environment. The extreme case are desktop FPSs where
rendering FoV is vastly greater than screen FoV.



Pupil swim also plays a role, but I think it's not the main issue here."


Looks like back to DK2 and the Vive I go for now, I find the warping when looking around at things to be intolerable personally :neutral: 
PatimPatam
Up and Coming
May 31, 2016
Well i'm not sure if it's pupil swim or the FOV mismatch mentioned by
DocOK, but i did notice this problem already when i tested the Crescent
Bay at OC1, and unfortunately i still find it in CV1; I can try to
minimize it by tilting the HMD downwards as
far as i can but then it makes it quite uncomfortable as it presses
hard against my cheeks. Didn't have this issue with the DK2 (only when
the software pre-warp wasn't working properly) and haven't noticed it
with the Vive either..



My guess is that simply for some head/face structures the relative
position between eyes and lenses makes pupil swim worse than average,
and that the new tilting mechanism while very good for general comfort
makes this harder from a pure optics point of view.
Personally i find this more distracting than the infamous "godrays" as
it means the world doesn't feel locked in place, and i can see people that have
similar problems experiencing discomfort because of this..



Anyway i understand it's all a matter of tradeoffs at this early stage,
but i can't wait until we have good enough eye-tracking and optics to
make this type of issues a thing of the past.
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