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  • VR180 Stereo video and perceived scale

Hello,

I would like to present you my personal understanding of how VR180 stereo video works with our brain. Especially stereo relation to perceived scale.
Feel free to check this info graphic and let me know your thoughts.

If you want to test this effect, open any passthrough video (or video with flat BG) and try moving "Horizontal offset" to negative values.
Also related effect to this is actual zooming, when a subject is close to the camera, try zooming out. What you notice that closer stuff is kind a moving slower into distance then the background. You kind a feel it is staying close due to larger stereo separation. But try it with forced mono, everything moves at same rate.

There is a second part that tries to extrapolate how this limits canon dual fisheye camera and its 60mm lens separation - why we can't force any major scale change by manipulating stereo in post production.

This is an open discussion, if someone has ideas on it, please share, I am all ears, thank you!

Sandi

    Sandi_SLR

    Interesting.

    I’m no expert, but the perceived scale doesn’t seem linear from close to far on the Canon. Closer objects seem slightly larger in scale vs. something in the background. Not sure if this is just the brain playing tricks on me.

        bacula8630 Yea, this is an ongoing issue we are trying to solve, we recently adopted modified post process approach to help with this, but we cannot eliminate it completely. That was the inspiration for this reasearch.

            Sandi_SLR

            My knowledge on this topic is limited, but my understanding is there isn’t a totally effective way to adjust the IPD in post.

            Because of the fixed perspective of each eye at the moment of capture, altering that in post causes convergence issues. Your brain naturally tries to adjust when viewing the IPD adjusted footage. But this causes eye strain as you try to focus near to far.

            Add to that, the fact that the Canon used a single sensor. I’m not sure if they optically squeeze the image circle for each eye to make it fit on the 3:2 full frame sensor. Similar to what an anamorphic lens does. But I would imagine that adds another layer of complexity to the issue.

            I would be interested in seeing some clips of test footage after the IPD has been altered. It would be interesting to see how watchable it would be.

                Sandi_SLR

                Thanks. I’ll give it a try in the meantime.

                I hope you guys can figure something out. Because there’s quite a few great scenes that have been hampered by the large scale.

                Good luck!

                And if you do apply a fix to some of the older scenes shot on the Canon rig. Please let us know so we can check them out.

                  Ah man... I was just going to stop doing computer stuff for the day... 🤣

                  I don't know much about this or computer vision in general but I think these are relevant links.
                  https://en.wikipedia.org/wiki/Vergence#Convergence
                  https://inst.eecs.berkeley.edu/~cs280/sp15/
                  ^ just the stereopsis parts

                  A wide convergence is for things far away (like stars in the sky light years away).
                  Narrow convergence angles are for stuff close up and make you go cross-eyed.
                  When things get too close they go beyond the "near point of convergence" making you see double.

                  It's good to keep things above the near point of convergence or it'll be hard to watch.

                  I found this formula in that eecs class (I filled in the variable names to make it readable)
                  baseline = IPD
                  convergence = (baseline / 2) / depth

                  If you could change the IPD for the video when it falls below the near point convergence, then it would avoid the double vision effect. The rest of the video could keep the default IPD. I think that would work in post since it's just for quick bursts when things get too close.

                  I know even less than @bacula8630 though so if changing the IPD or horizontal offset in post causes headaches then that's probably not a good route.

                  I think this all lines up but I'm not sure if it totally checks out. I didn't have a chance to change the IPD to test this setup.

                    dudder Hey, this is actually more important on how they shoot on set. Just avoid going that close. There is a limit on how much you can fix the doubling effect since if the subject gets too close, the left and right image differ so much the brain cant join them into coherent image.
                    But what you describe is actually autofocus feature, just limited to really close stuff only.

                        dudder When things get too close they go beyond the "near point of convergence" making you see double.

                        Or see one, me and this female I use date we use to be upclose cuddling and what not and we be so close are eyes would turn into one, we use to think it was weird how it did that, lol make you look like you had one eye. It's cus you looking at an object up close, the closer you get to the middle of eyes you looking at it crossed eyed.

                        Put two fingers up in front of your face and move it closer to the middle of your eyes touching your forehead, you'll see one fat finger. Lol

                        It does that in vr too, I would see viewers complain, "why I see double during close ups" I'd be there just thinking well it does that in real life" lol 😆

                        To me that double vision up close just added more realness, but only during close up kissing it was ok, during close up 69 or ass eating I'd rather have no double vision during them parts. 👍

                          Sandi_SLR Hey, this is actually more important on how they shoot on set. Just avoid going that close

                          Oh God please don't say that

                          Xzibit A

                          Sum 69 are way to far 👆, sum are even further 🤦‍♂️, the female will be there asking you to eat her, and I'm thinking well I would if you come closer. Lol

                          Xzibit b,
                          This how close a 69 should be 👇

                          Closer the better, imo

                          Even in like laying cg, she'll lean in, and say you like my tits in your face, and I'm like yeah but come closer, lol ...smother me, motorboat me with them! GET CLOSER! just don't get to close the cam accidently moves. Lol 👍

                              Sandi_SLR I see what you're saying about how shifting the horizontal offset makes it similar to autofocus. I tried messing around with that and at least the close up images look better when they're maxed out at 7.5+. I'm not sure if there's a way to stitch the image back together without goofy looking scale downsides like you mentioned. At least the autofocus is going to be cool to have!

                                Vrsumo2017 I mean... in real life you don't even see pussy when you licking it. You see the belly maybe but you don't see pussy. One have to have eyes inside his mouth to see pussy while licking it.

                                    So if you want to focus your eyes on close-ups it has to be further away. Which in missionary and pussy-licking or kissing is not an option, you can't reach it.
                                    Or either its like in real life so close to your face that you can't focus on it.
                                    Put your hand in front of your face and imagine its a girls face and try to focus on it. In real life there is no such a thing as focusing on an object that is too close! But do we complain about it? That's our physiological limitations, no way to do that and that's ok. That's how you feel that something / or someone is too close.
                                    By the way, who's kissing with his eyes open?

                                    metaverse You see the belly maybe

                                    Lol, or looking up at under boobish, 👍😏

                                    Lol, or if its non shaved you looking at hair, or if its shaved you might be looking at razor bumps 😜

                                      metaverse ima post this here as a suggestion since we discussing upclose oral

                                      But I've suggested on forums before why studios don't do pov oral with the male actors during 69

                                      It'll look like this

                                      Or do standing pov oral like this

                                      I think it would work but we would have to see what kinda feed back it gets from the viewers, I would do a studio just focused on upclose pov trying to get them kinda shots, 69, kissing, sucking tits, sucking ass and what not. It be sum kinda pov oral fetish I guess

                                      And please no one say kissing pov can't be done cuz look at this shot

                                      And heres how sucking tittys pov can be done

                                      See how you see down dudes nose, all she had to do was stick a titty in his mouth and you got your self sum pov titty sucking.

                                      It can be done, imo.

                                      And tha camera that far back you really don't see guys nose down depending on how you got your tilt with the tilt option in vr players like deo.

                                      Thought I throw this out there as a suggestion cuz there's no real pov of oral situation.

                                      👍😏

                                          So I tried adjusting the horizontal offset on a Melody Marks JAV VR scene where the scale was too small.

                                          While it increase the scale nicely when she was close to the camera. It wreaked havoc to the background. Where the images from both eyes no longer converged properly. And gave me double vision.

                                          I think I prefer to simply zoom in or out to fix the scale. Versus playing with the horizontal offset. Yes, zooming will introduce geometric distortion, but it’s much more watchable to me personally.

                                          Unfortunately, I don’t really see adjusting the horizontal offset as a long term solution. ☹️

                                            bacula8630 Adjusting horizontal offset was only an example that mimics what the initial post is talking about.
                                            This step is done by post production when they prepare the video you watch, so they kind a set the default value.