7 ms·

Keep doing that and you'll go blind

95 points by chmike 17y ago

alextgordon 17y ago
The article mentions binocular dysphoria quite a bit. The wikipedia article is amusing: http://en.wikipedia.org/w/index.php?title=Binocular_Dysphoria&oldid=343315081 http://en.wikipedia.org/w/index.php?title=Binocular_Dysphori... . It appears the term was made up.
deleted 17y ago
[deleted]
sdfx 17y ago
From the article: The Wikipedia entry on depth perception (an excellent read) lists ten different cues that your brain uses to figure out exactly how far away something is. Parallax is just one of them. Since the various movie and television display technologies only offer parallax-based depth cues, your brain basically has to ignore several other cues while you're immersed in the world of Avatar. This is why the 3D of films doesn't feel quite right. I agree that 3D films often feel a bit weird, but I'm not 100% sold on his idea of why this should be. The Wikipedia article names many visual cues that are present in 3D movies as well (e.g. relative size, perspective, texture & lighting etc.). It seems conceivable that your brain is "tricked" and has to adapt to the new situation, I just don't know if his reasoning is valid.
- pavel_lishin 17y ago
  Most of the cues listed seem like they are still used in a 3D film - aerial perspective, relative size, occlusion, etc can be stimulated and peripheral vision is irrelevant.
- barrkel 17y ago
  From the Wikipedia article, of the 13 depth cues, only 2 aren't properly present in 3D films - accommodation (having to focus the eyes) and peripheral vision - and the peripheral vision cue is also missing from regular cinema, TV etc. So are there more things going on here? It seems unlikely to me that the focus of the eye lens is having a big impact.
  - sdfx 17y ago
    I don't know about the accommodation, but isn't the loss of peripheral vision like looking out of a window? Think of the movie screen as a big window into the world. Not on the list (I think) but what about head movement of the viewer? If I move my head slightly to one side the picture stays the same while I expect to look behind an object.
  - sp332 17y ago
    Accommodation makes a big difference if you're near- or far-sighted.
tocomment 17y ago
Doesn't normal 2D TV also force you to ignore even more depth perception cues? We still have relative size, parralax, etc telling us that the things on the screen are at different depths.
- daveungerer 17y ago
  Did we read the same article? 2D TV doesn't trick the brain into thinking it's 3D. Your brain can clearly see it's 2D. When you view fake 3D, the brain thinks it's 3D. But now that your brain is in 3D mode, it has to turn off processing for a lot of cues it would normally take into account, due to the fake 3D not being a complete simulation of reality.
  - tocomment 17y ago
    The article says there are 10 depth perception cues. ONE of them is showing different images to each eye. 2D images do have some of the 10 cues. What is special about this ONE cue and not the ones that a 2D image has? I.e., why does your brain turn off processing for the differing images to each eye cue but not for the parralax cue, etc?
    - daveungerer 17y ago
      What's special about this ONE cue? Ummm... how about the fact that it can trick your brain into believing it's viewing 3D without including most of the others? I mean... you just said a 2D image doesn't have this one cue, but has the others. That, by definition, makes it special. But your second paragraph show's me this is all based on confusion. The parallax cue and processing different images for each eye are the same thing, not 2 different things as you're implying. And that's the one of the cues that's NOT turned off. I'm not defending what the author is saying. I just feel you should read the article again, because your statements don't seem to address anything said in the article.
- bartl 17y ago
  I think you must be referring to perspective... which gives indeed an idea of 3D. Medieval paintings lacked perspective. But technically it's still 2D: both eyes see the same thing. We are used to 2D: if you look around with one eye, or at very long distances: the moon, the sun and the stars are in 2D. And we're used to 2D in drawings, paintings and photographs. 3D tries to trick you into seeing 3D by showing a different picture for each eye, but the illusion is far from perfect: according to this article we receive clues that point in different directions. And that, it claims, isn't healthy in the long run.
tocomment 17y ago
I wish we could just move to holograms. What's holding us back exactly? I could never find a straight answer.
- gjm11 17y ago
  Updating them in real time is difficult. You need a feature size comparable to the wavelength of the light being used, which would mean somewhat less than 1um. The smallest pixel sizes in LCDs these days are on the order of 5um across or so. Other kinds of imagers (DLP, for instance) are comparable or worse.
  - tocomment 17y ago
    I don't understand. Can't we just have holograms with lower resolution?
    - eru 17y ago
      Holograms don't work that way. It's a bit like a fourier-transform: One pixel on your holographic display does not correspond to one tiny feature in your image. (Perhaps you can find more answers in http://en.wikipedia.org/wiki/Computer_Generated_Holography http://en.wikipedia.org/wiki/Computer_Generated_Holography and http://en.wikipedia.org/wiki/Holography http://en.wikipedia.org/wiki/Holography for the basics.)
  - Splines 17y ago
    I played a 3-d game that had the same game mechanics as Dragon's Lair (the protagonist was a time-traveling cowboy). While each scene was pre-rendered (it was pre-recorded live action), the effect was impressive, especially considering this was probably about 15 years ago. edit: Here it is: http://en.wikipedia.org/wiki/Time_Traveler_(video_game) http://en.wikipedia.org/wiki/Time_Traveler_(video_game)
- ars 17y ago
  Computers are not fast enough yet to calculate them in real time.
JunkDNA 17y ago
I really wish there was a way to do 3D that allowed your eyes and brain to naturally do what they do in the real world, though perhaps we're a long way from that? Anyone familiar with or doing any research on better mechanisms for 3D? I have yet to experience any sort of 3D entertainment that isn't (at least initially) disorienting. The need to wear glasses constantly ruins the experience. But even beyond that, the unnatural way the camera "forces" you to focus on things in the foreground also feels wrong to me and breaks the illusion. If the main character is front and center, but I want to stare at the wall right behind him, it shouldn't be blurry. But it often is blurry because of the camera's depth of field. You sort of feel like an unseen hand is forcing you to look at certain things and not others.
- iujhygfbh 17y ago
  In the real world - you don't really see 3D very much. Your eyes are only 0.1m apart so anything more than 3-4m away isn't really in 3d anyway. Everything in the distance is handled by your knowledge of it's relative size and position - which works just as well on a 2d screen anyway. Try it, cover one eye and look at the scene, you will see a difference on your desk, but no difference for the scene outside your window. That's why most 3d movies have lots of things flying at you and other gimmicks - it's because otherwise there wouldn't be much 3d-ness
  - JunkDNA 17y ago
    Agreed. This is one of the reasons a sufficiently large (non-3D) IMAX screen provides an incredibly immersive experience for all kinds of long distance "big" shows like "Everest" or my childhood favorite "The Dream is Alive". You get all the right visual cues to feel as though you're looking out an airplane window zooming over terrain or standing on a mountain peak. In my experience, the IMAX shows that have been less impressive have been the ones relying on lots of close-up work. Undersea ones in particular don't feel as immersive because the camera needs to be too close to the subject in order to have sufficient detail. I would argue though that just because you don't see in 3D at a long distance, doesn't mean that the little area at 3-4m away isn't important for traditional movies. Most personal interaction is at that distance. In fact, a lot of the dialog scenes in movies are shot as though you're standing right there looking the actors in the face. I think good 3D in that range is also what pulls you into the scene and really makes you feel like you are there. There were a couple of scenes in Avatar where this was really well done, most notably when they were in the thick of the jungle and insects were buzzing around your head. That little detail really made me feel like I was standing there.
JeffJenkins 17y ago
I have Amblyopia -- an eye condition where the image from one eye is partially suppressed by the brain. I'd been wondering what a 3D movie would do to me for a while since parallax doesn't work when you brain is processing the images from each eye as separate. It turns out that the answer is not much of anything, but I still have to wear the glasses to filter out the second image. Although I'm sure it will be nice for some people, I'm personally hoping that this doesn't catch on. It's pretty annoying to pay extra and have to wear special glasses (on top of my real glasses) when I'm physically incapable of benefiting from them.
- aarongough 17y ago
  Similar situation here. I was born with one eye only having about 10% of the nerves that it was supposed to, and the ones I have are only connected to the peripheral areas of the retina. I've never been excited about 3D movies or games because they simply do not work for me, which was always a source of disappointment when I was a kid. Personally I really can't see it catching on... Who wants to have to wear special glasses while sitting in their house watching TV?
gjm11 17y ago
This seems like sheer alarmism. Made-up pseudomedical terminology? Check. Won't-somebody-please-think-of-the-children plea? Check. Confident claims of what's likely to happen, right alongside complaints that no one has done any research? Check. (I originally had a paragraph here about how he links to the Wikipedia article on depth perception and says: here are all the distance cues your brain uses; 3-d movies only provide one of them; oh noes, your brain will get all confused -- whereas in fact almost all the distance cues listed there are available in 3-d movies, and indeed almost all of them are available in plain ol' 2-d movies. But someone else already did that in more detail, so I shan't bother.) Incidentally, I see that Mark Pesce's own Wikipedia page describes him inter alia as a "hack and shameless self-promoter". I'm about to delete that since it's obviously unencyclopedic and non-NPOV, but this article sure makes it look like it might be true.
- gojomo 17y ago
  On the other hand: we've had 3D in various forms, on and off, for over 50 years. It's always been interesting; it's never persisted as the main way of viewing. Perhaps this is the reason why. Pesce is not making things up; he's got real experience with a real system that didn't come to market, and the same effects have been covered in other news outlets: "The Problem With 3-D: It hurts your eyes. Always has, always will." http://www.slate.com/id/2215265/pagenum/all/ http://www.slate.com/id/2215265/pagenum/all/
- ableal 17y ago
  If you read the comments, quite a bit further down, a colleague (Rowley) pipes up with this: The data that put a bullet into Segas plans came from a study they commissioned to be done by SRI. Very few ever got to see those results since I don't believe Sega ever released them. But some of us got to be privy to the findings. In brief there was a small percentage of folks who retained depth perception issues for periods of time ranging from 15 minutes to a couple of hours. SRI determined that a small percentage of that group could suffer permanent loss of depth percentage. The potential liability issues were staggering and the plan to put headmounts on the worlds game playing kids was killed - kaput!. This seems believable, and SRI is a reputable company.
blue1 17y ago
Mark Pesce, technopagan and inventor of VRML. Interesting guy.
xenonite 17y ago
moving your head doesn't change the picture. another limitation: the surrounding light of your living room doesn't influence the screen. This would be the only current limitations, right? Those devices could change that: "Towards Passive 6D Reflectance Field Displays" http://www.mpi-inf.mpg.de/resources/prfdisplays/ http://www.mpi-inf.mpg.de/resources/prfdisplays/
- epochwolf 17y ago
  There is an additional limitation I noticed with 3D movies. You are stuck with the focus of the camera used, you can't bring distant objects into focus because they are out of focus on the film.
  - nitrogen 17y ago
    That is something that directors will have to learn to work with when filming 3D. It's especially when video games use focal blur and motion blur. Trying to focus on a distant (or really close) object causes a headache because it never comes into focus, and the interactive nature of games increases the expectation that I should be able to look where I want to look, unlike movies.
noonespecial 17y ago
If the brain is malleable to change itself to a depth perception compromised state due to exposure, isn't it malleable to change itself back when the exposure is removed? Or it might just be malleable to figure the whole thing out after a little while and make it a non-issue. As for me, I have very poor depth perception anyway thanks to having lousy vision in one eye, but the effect in the movies works quite well for me. Perhaps (diabolical laugh) the score will finally be evened up!
kostko 17y ago
I will tell you about my experience some time after watching a 3d film which I won't mention... It started with normal films on my lcd. I could see the difference, as if I could somehow sense the depth of 2d movie in a way I couldn't before. This happened also with one 2d drawn betting chip with some shading that I was cropping at work. One more item that gave the same feeling was the hologram sticker on a nokia battery, I could never tell what was the big fuss about hologram stickers, as I could never see the hologram in 3d before, it was always just a smudge. These symptoms have ceased after some time, but I can still see the hologram in '3d', the way I couldn't before. It's nice to read that these symptoms can exist, now I know it wasn't all just in my mind...
pso 17y ago
The Wikipedia article refers to 13 cues total. Only 2 of which are under our physical control - convergence (our eyes crossing to focus) and accomodation (changing the lens shape). Providing separate images to each eye, triggers the 3d processing mechanism in a way that TV doesnt. For lifetimes, we expect if objects approach or recede, we adjust our focus, ie converge and accomodate (there's obviously a very high evolutionary advantage to getting the distances right). From what some describe, we keep attempting to focus when watching 3D and failing. Also, they're both feedback loops, there's some convergence/lens bending, the image gets a bit clearer, we keep going in the same direction, I'd guess that the brain keeps trying, fails and then reverts to focus on the 2d planes presented, 1000s of times throughout the movie, this is what causes the brain and eyeache. Possibly we can adapt, and naturally switch in and out of movie mode without discomfort, but we'd need to have movies worth seeing.

95 points by chmike 17y ago

The article mentions binocular dysphoria quite a bit. The wikipedia article is amusing: http://en.wikipedia.org/w/index.php?title=Binocular_Dysphoria&oldid=343315081 http://en.wikipedia.org/w/index.php?title=Binocular_Dysphori... . It appears the term was made up.

deleted 17y ago

[deleted]

sdfx 17y ago

From the article: The Wikipedia entry on depth perception (an excellent read) lists ten different cues that your brain uses to figure out exactly how far away something is. Parallax is just one of them. Since the various movie and television display technologies only offer parallax-based depth cues, your brain basically has to ignore several other cues while you're immersed in the world of Avatar. This is why the 3D of films doesn't feel quite right. I agree that 3D films often feel a bit weird, but I'm not 100% sold on his idea of why this should be. The Wikipedia article names many visual cues that are present in 3D movies as well (e.g. relative size, perspective, texture & lighting etc.). It seems conceivable that your brain is "tricked" and has to adapt to the new situation, I just don't know if his reasoning is valid.

pavel_lishin 17y ago
Most of the cues listed seem like they are still used in a 3D film - aerial perspective, relative size, occlusion, etc can be stimulated and peripheral vision is irrelevant.
barrkel 17y ago
From the Wikipedia article, of the 13 depth cues, only 2 aren't properly present in 3D films - accommodation (having to focus the eyes) and peripheral vision - and the peripheral vision cue is also missing from regular cinema, TV etc. So are there more things going on here? It seems unlikely to me that the focus of the eye lens is having a big impact.
- sdfx 17y ago
  I don't know about the accommodation, but isn't the loss of peripheral vision like looking out of a window? Think of the movie screen as a big window into the world. Not on the list (I think) but what about head movement of the viewer? If I move my head slightly to one side the picture stays the same while I expect to look behind an object.
- sp332 17y ago
  Accommodation makes a big difference if you're near- or far-sighted.

tocomment 17y ago

Doesn't normal 2D TV also force you to ignore even more depth perception cues? We still have relative size, parralax, etc telling us that the things on the screen are at different depths.

daveungerer 17y ago
Did we read the same article? 2D TV doesn't trick the brain into thinking it's 3D. Your brain can clearly see it's 2D. When you view fake 3D, the brain thinks it's 3D. But now that your brain is in 3D mode, it has to turn off processing for a lot of cues it would normally take into account, due to the fake 3D not being a complete simulation of reality.
- tocomment 17y ago
  The article says there are 10 depth perception cues. ONE of them is showing different images to each eye. 2D images do have some of the 10 cues. What is special about this ONE cue and not the ones that a 2D image has? I.e., why does your brain turn off processing for the differing images to each eye cue but not for the parralax cue, etc?
  - daveungerer 17y ago
    What's special about this ONE cue? Ummm... how about the fact that it can trick your brain into believing it's viewing 3D without including most of the others? I mean... you just said a 2D image doesn't have this one cue, but has the others. That, by definition, makes it special. But your second paragraph show's me this is all based on confusion. The parallax cue and processing different images for each eye are the same thing, not 2 different things as you're implying. And that's the one of the cues that's NOT turned off. I'm not defending what the author is saying. I just feel you should read the article again, because your statements don't seem to address anything said in the article.
bartl 17y ago
I think you must be referring to perspective... which gives indeed an idea of 3D. Medieval paintings lacked perspective. But technically it's still 2D: both eyes see the same thing. We are used to 2D: if you look around with one eye, or at very long distances: the moon, the sun and the stars are in 2D. And we're used to 2D in drawings, paintings and photographs. 3D tries to trick you into seeing 3D by showing a different picture for each eye, but the illusion is far from perfect: according to this article we receive clues that point in different directions. And that, it claims, isn't healthy in the long run.

tocomment 17y ago

I wish we could just move to holograms. What's holding us back exactly? I could never find a straight answer.

gjm11 17y ago
Updating them in real time is difficult. You need a feature size comparable to the wavelength of the light being used, which would mean somewhat less than 1um. The smallest pixel sizes in LCDs these days are on the order of 5um across or so. Other kinds of imagers (DLP, for instance) are comparable or worse.
- tocomment 17y ago
  I don't understand. Can't we just have holograms with lower resolution?
  - eru 17y ago
    Holograms don't work that way. It's a bit like a fourier-transform: One pixel on your holographic display does not correspond to one tiny feature in your image. (Perhaps you can find more answers in http://en.wikipedia.org/wiki/Computer_Generated_Holography http://en.wikipedia.org/wiki/Computer_Generated_Holography and http://en.wikipedia.org/wiki/Holography http://en.wikipedia.org/wiki/Holography for the basics.)
- Splines 17y ago
  I played a 3-d game that had the same game mechanics as Dragon's Lair (the protagonist was a time-traveling cowboy). While each scene was pre-rendered (it was pre-recorded live action), the effect was impressive, especially considering this was probably about 15 years ago. edit: Here it is: http://en.wikipedia.org/wiki/Time_Traveler_(video_game) http://en.wikipedia.org/wiki/Time_Traveler_(video_game)
ars 17y ago
Computers are not fast enough yet to calculate them in real time.

JunkDNA 17y ago

I really wish there was a way to do 3D that allowed your eyes and brain to naturally do what they do in the real world, though perhaps we're a long way from that? Anyone familiar with or doing any research on better mechanisms for 3D? I have yet to experience any sort of 3D entertainment that isn't (at least initially) disorienting. The need to wear glasses constantly ruins the experience. But even beyond that, the unnatural way the camera "forces" you to focus on things in the foreground also feels wrong to me and breaks the illusion. If the main character is front and center, but I want to stare at the wall right behind him, it shouldn't be blurry. But it often is blurry because of the camera's depth of field. You sort of feel like an unseen hand is forcing you to look at certain things and not others.

iujhygfbh 17y ago
In the real world - you don't really see 3D very much. Your eyes are only 0.1m apart so anything more than 3-4m away isn't really in 3d anyway. Everything in the distance is handled by your knowledge of it's relative size and position - which works just as well on a 2d screen anyway. Try it, cover one eye and look at the scene, you will see a difference on your desk, but no difference for the scene outside your window. That's why most 3d movies have lots of things flying at you and other gimmicks - it's because otherwise there wouldn't be much 3d-ness
- JunkDNA 17y ago
  Agreed. This is one of the reasons a sufficiently large (non-3D) IMAX screen provides an incredibly immersive experience for all kinds of long distance "big" shows like "Everest" or my childhood favorite "The Dream is Alive". You get all the right visual cues to feel as though you're looking out an airplane window zooming over terrain or standing on a mountain peak. In my experience, the IMAX shows that have been less impressive have been the ones relying on lots of close-up work. Undersea ones in particular don't feel as immersive because the camera needs to be too close to the subject in order to have sufficient detail. I would argue though that just because you don't see in 3D at a long distance, doesn't mean that the little area at 3-4m away isn't important for traditional movies. Most personal interaction is at that distance. In fact, a lot of the dialog scenes in movies are shot as though you're standing right there looking the actors in the face. I think good 3D in that range is also what pulls you into the scene and really makes you feel like you are there. There were a couple of scenes in Avatar where this was really well done, most notably when they were in the thick of the jungle and insects were buzzing around your head. That little detail really made me feel like I was standing there.

JeffJenkins 17y ago

I have Amblyopia -- an eye condition where the image from one eye is partially suppressed by the brain. I'd been wondering what a 3D movie would do to me for a while since parallax doesn't work when you brain is processing the images from each eye as separate. It turns out that the answer is not much of anything, but I still have to wear the glasses to filter out the second image. Although I'm sure it will be nice for some people, I'm personally hoping that this doesn't catch on. It's pretty annoying to pay extra and have to wear special glasses (on top of my real glasses) when I'm physically incapable of benefiting from them.

aarongough 17y ago
Similar situation here. I was born with one eye only having about 10% of the nerves that it was supposed to, and the ones I have are only connected to the peripheral areas of the retina. I've never been excited about 3D movies or games because they simply do not work for me, which was always a source of disappointment when I was a kid. Personally I really can't see it catching on... Who wants to have to wear special glasses while sitting in their house watching TV?

gjm11 17y ago

This seems like sheer alarmism. Made-up pseudomedical terminology? Check. Won't-somebody-please-think-of-the-children plea? Check. Confident claims of what's likely to happen, right alongside complaints that no one has done any research? Check. (I originally had a paragraph here about how he links to the Wikipedia article on depth perception and says: here are all the distance cues your brain uses; 3-d movies only provide one of them; oh noes, your brain will get all confused -- whereas in fact almost all the distance cues listed there are available in 3-d movies, and indeed almost all of them are available in plain ol' 2-d movies. But someone else already did that in more detail, so I shan't bother.) Incidentally, I see that Mark Pesce's own Wikipedia page describes him inter alia as a "hack and shameless self-promoter". I'm about to delete that since it's obviously unencyclopedic and non-NPOV, but this article sure makes it look like it might be true.

gojomo 17y ago
On the other hand: we've had 3D in various forms, on and off, for over 50 years. It's always been interesting; it's never persisted as the main way of viewing. Perhaps this is the reason why. Pesce is not making things up; he's got real experience with a real system that didn't come to market, and the same effects have been covered in other news outlets: "The Problem With 3-D: It hurts your eyes. Always has, always will." http://www.slate.com/id/2215265/pagenum/all/ http://www.slate.com/id/2215265/pagenum/all/
ableal 17y ago
If you read the comments, quite a bit further down, a colleague (Rowley) pipes up with this: The data that put a bullet into Segas plans came from a study they commissioned to be done by SRI. Very few ever got to see those results since I don't believe Sega ever released them. But some of us got to be privy to the findings. In brief there was a small percentage of folks who retained depth perception issues for periods of time ranging from 15 minutes to a couple of hours. SRI determined that a small percentage of that group could suffer permanent loss of depth percentage. The potential liability issues were staggering and the plan to put headmounts on the worlds game playing kids was killed - kaput!. This seems believable, and SRI is a reputable company.

blue1 17y ago

Mark Pesce, technopagan and inventor of VRML. Interesting guy.

xenonite 17y ago

moving your head doesn't change the picture. another limitation: the surrounding light of your living room doesn't influence the screen. This would be the only current limitations, right? Those devices could change that: "Towards Passive 6D Reflectance Field Displays" http://www.mpi-inf.mpg.de/resources/prfdisplays/ http://www.mpi-inf.mpg.de/resources/prfdisplays/

epochwolf 17y ago
There is an additional limitation I noticed with 3D movies. You are stuck with the focus of the camera used, you can't bring distant objects into focus because they are out of focus on the film.
- nitrogen 17y ago
  That is something that directors will have to learn to work with when filming 3D. It's especially when video games use focal blur and motion blur. Trying to focus on a distant (or really close) object causes a headache because it never comes into focus, and the interactive nature of games increases the expectation that I should be able to look where I want to look, unlike movies.

noonespecial 17y ago

If the brain is malleable to change itself to a depth perception compromised state due to exposure, isn't it malleable to change itself back when the exposure is removed? Or it might just be malleable to figure the whole thing out after a little while and make it a non-issue. As for me, I have very poor depth perception anyway thanks to having lousy vision in one eye, but the effect in the movies works quite well for me. Perhaps (diabolical laugh) the score will finally be evened up!

kostko 17y ago

I will tell you about my experience some time after watching a 3d film which I won't mention... It started with normal films on my lcd. I could see the difference, as if I could somehow sense the depth of 2d movie in a way I couldn't before. This happened also with one 2d drawn betting chip with some shading that I was cropping at work. One more item that gave the same feeling was the hologram sticker on a nokia battery, I could never tell what was the big fuss about hologram stickers, as I could never see the hologram in 3d before, it was always just a smudge. These symptoms have ceased after some time, but I can still see the hologram in '3d', the way I couldn't before. It's nice to read that these symptoms can exist, now I know it wasn't all just in my mind...

pso 17y ago

The Wikipedia article refers to 13 cues total. Only 2 of which are under our physical control - convergence (our eyes crossing to focus) and accomodation (changing the lens shape). Providing separate images to each eye, triggers the 3d processing mechanism in a way that TV doesnt. For lifetimes, we expect if objects approach or recede, we adjust our focus, ie converge and accomodate (there's obviously a very high evolutionary advantage to getting the distances right). From what some describe, we keep attempting to focus when watching 3D and failing. Also, they're both feedback loops, there's some convergence/lens bending, the image gets a bit clearer, we keep going in the same direction, I'd guess that the brain keeps trying, fails and then reverts to focus on the 2d planes presented, 1000s of times throughout the movie, this is what causes the brain and eyeache. Possibly we can adapt, and naturally switch in and out of movie mode without discomfort, but we'd need to have movies worth seeing.