Originally Posted by tgm1024 There is no up/down parallax relative to your eyes when you tip your head in real life.
Originally Posted by cakefoo
The eyes, brain and skull are all attached to each other, so there is never a conflict or misalignment.
I know you are both deadset on figuring out why I can't grasp this simple point, but you are so set on doing so you are completely missing the very simple point I am making:
What you both said above is not true.
tmg there IS up down parallax (some) in real life.
Cake your eyes are NOT attached to your skull (at least not in the way your headlights are attached to your car).
That's what I am getting at with all this eyeball roll and diagrams...
This is what it comes down to, cakefoo made the perfect example when he says your eyes are attached to your skull so stay left right aligned when you tilt yoru head.
Again it comes down to eyeball roll.
Again when you tilt your head, if your eyes really WERE attached to your skull, they would stay level with your jawline and not the horizon. Thus if you tilt your head to the left, the left eye is lower than the right and the image each sees is a perfect horizontal pan from the other like this:
Both eyes tilted and properly left to right separated. But that's not what happens.
As you tilt your head to the left, both eyes rotate in your skull so they are no longer aligned with your jawbone, they remain aligned with the horizon (obviuos to a point, they don't roll a full 90 degrees or anything). Your right eye ends up higher than your left and both capture images even with the horizon - or in other words vertically offset. What you really see is more like this:
(note both sets of pictures are supposed to be left right pairs but due to formatting they may show up over each other)
"But that's not at all what I see!" I hear you exclaim. "I do not see the world as still level!"
Your eyes do. I assure you, if you think about it for just a moment (let go of your certainty that you are right about how your eyes work and follow the logic of rotating eyeballs and tilted head). But your brain, using information from your ears for balance and it's own knowledge of how your body is moving corrects for this. Thats the point I am making all along: Your brain is good enough to do more than simply look at a left right parallax and draw depth, it does much more manupilating and thats why I beleive it's entirely possible it can go all the way to up down parallax to draw depth data.
Here is one last attempt to illsutrate this so there is no confusion. The face on the left is what we normally are doing, level head, eyes both parallel to the horizon each capturing a true left right parallax offset image. The middle is what you both assume is happening when you tilt your head, head tilted, eyes staying level with the tilt of the head. On the right is what really happens: Head tilts, eyes roll to stay level with horizon, you end up with one camera effectively above and to the side of the other creating both horizontal and veritcal parallax offset from each other.
Please excuse my hideous MS Paint skills. The red lines represent the orientation of each eye interms of what it woudl individually see as "horizontal".
Cakefoo I believe you do 3D photography. You have two cameras stuck together side by side right? And when you tip them, they do what the middle face does right? Take one and lower it compared to the other to capture what the right hand face would see. Tell me there is no up down parallax there.
Now think about this... if your brain can fix that so smoothly you had no idea it even happened until I explained it all to you, isn't it possible it can go even further?