0941: "Depth Perception"

[spriteless]

1000x is not enough difference for humans to see the stars. The distance between the hemispheres, hell, even the difference between summer and winter months is not enough for that. As Douglas Adams said, infinity is staring at the stars and being unable to tell light-years from light-millenia.

Cool idea for clouds, though.

[solobutterfly]

For those wanting stellar stereo images check out: http://nzphoto.tripod.com/astro/3dastro/

I've now spent the last half hour googling stereo images instead of school work. XKCD, you keep doing this to me!

[plasticup]

It has probably bee said already, but with four strips of polarizing material (every science department has them) and two projectors (borrow them from your nearest Comp. Sci professor) you can make your own 3-D movie studio. It is dead simple. One polarizing filter goes over each projector and the corresponding one goes over each eye.

[fealuinix]

Is ~100m really enough for stars, though?

2 AU (~3 x 10^11 m), or the diameter of the earth's orbit*, causes just enough parallax to gauge the distance of some of the nearer stars with sensitive instruments. I personally doubt that the earth's diameter would be enough to visually tell the parallax of the relatively much-closer gas giants.


*Well, twice the mean radius. Close 'nuff.

[TaylorP]

It has probably bee said already, but with four strips of polarizing material (every science department has them) and two projectors (borrow them from your nearest Comp. Sci professor) you can make your own 3-D movie studio. It is dead simple. One polarizing filter goes over each projector and the corresponding one goes over each eye.

I've always wanted to get my hands on some of the circular polarizing lenses that they use for RealD 3D. Apparently the refresh rate on most computer monitors is too low to effectively display 3D that way, though. RealD's site suggests a refresh rate of 120Hz for ideal viewing.

[BytEfLUSh]

Damn, I guess there are a lot of great 3D images in this thread, but I just can't figure out how to view those side-by-side ones. I've read a lot of guides on how to "get them to work", but still no luck... :\

[KShrike]

If this can actually work, then that would be amazing.
It wouldn't be the same as actually walking on the clouds, though (which is impossible unless you are a pegasus, which doesn't exist anyway)

[jackal]

When I see a full moon I always try to picture the state of Texas overlaying it (you know, like we all learn in middle school some time) and then I think of how small it actually is Then again when I imagine the distance between the moon and our earth I just realise how big Texas is

EDIT; or was it the USA? I don't remember, middle school is waaaaay long ago

Lemme guess...you went to school in Texas. Neither of my schools in California (third largest state) or Alaska (bigger than y'all down in Texas) ever tried superimposing my home state on the moon. I think Texans just have an infatuation with the size of their state.

Don't let me remind you that if you cut Alaska in half, Texas'd be the third-largest state. Or even better: wait until low tide and then cut Alaska in thirds, making Texas the fourth-largest state.

Here's a map: http://alaska.org/bigalaska/howbigalaska.htm

[JamusPsi]

That said you might find this book interesting: http://www.amazon.co.uk/dp/0465009131. She writes about the experience of perceiving stereopsis after 30 years without. I spent a bunch of time last year reading about stereo vision and talking to ophthalmologists and sadly what worked for her wouldn't work for me - having differing amounts of myopia in each eye as well as misaligned eyes doesn't seem to be solvable without an arrangement of lenses and/or prisms to correct magnification, focus and alignment at the same time.

I ordered the book. I might just owe you a beer. Or a lot of beer. Thank you.

[buddy431]

For a well done, computer generated stereoscopic view of stars, the recent Hubble 3D IMAX film had some pretty good shots. I sort of know one of the guys who worked on the shot into the Orion Nebula, so he showed us that scene (as well as a bunch of other cool 3D stuff) on a big projector, which was pretty awesome.

[gormster]

*edit: source + more http://www.flickr.com/photos/53241841@N ... 052955906/

Okay, I've had this problem before, where people show me one of these, and it's backwards. I.e., the left eye image is on the right, and thus the depth of field is inverted.

However, I've also had people insist that it's not backwards, that it looks fine. So, here's that same image, with the eyes reversed. This one below, by the way, looks "correct" for me - that is, the clouds at the top of the picture are more distant, and the ground slopes away from you. The one above has inverted depth-of-field: the clouds at the top look closer and the ground slopes towards me, like I'm looking up at the ceiling.

I'd love to know if I have some sort of bizarre inverted-depth-of-field eye/brain condition. So, look at the picture above, and this one, and tell me which one looks wrong.

[vonpixel]

Registered just to say I have done this.
Only it was on the top a building (30th floor) and it was with 2 RED cameras (the older ones, not the new epic or anything) and they were about 400 (or maybe 300) feet apart. It took us a while to the convergence into the right spot but once we did....

The effect was pretty amazing. Especially when you watch it back in Real D or with polarization and not Red/Blue. The cameras were pointed downwards at the city. It basically felt like a tilt shift focus.

[samwyse]

Sort-of on topic, I own a copy of this book: Lincoln in 3-D

Here's an interview with the authors.

Seriously cool.

[dcigary]

Here's the Golden Gate pic quick-n-dirty hacked up. MUCH better when the images are reversed. That was my question and why I came in here to see if anyone noticed that the left image was on the right and the right image was on the left. It didn't make any sense to me then, but now that I see this it makes perfect sense! Interestingly, at least to me, is that the image seems to be tilt-shift focused, or at least my mind make it seem like that huge bridge is just a Lego re-creation...

http://img708.imageshack.us/img708/3163/goldengatebetter.jpg

Great pic, BTW!

[rapturemachine]

Spoiler:

Regarding the stars thing, if you ever wander through the southern hemisphere on a cloudless, dark area during a moonless night, you can certainly experience the depth of space with just a few minutes of concentration. Just lay on your back looking at the sky for a while. Af first it will look flat just as it has always done. But then you'll notice that in the middle of the milky way (which is much more visible and defined in the shouthern sky) there's an area that faintly bulges. That's the center of the galaky, visible behind the closer spirals. You can see a difference between the area with identifiable stars (the closer arms) and the part that's just a shapeless cloud. If you follow the arm to the sides, you'll notice there's a part that also somewhat bulges before becoming fainter. You are looking at the arm along its tangent. If you look up further to the zenith you will notice, slightly above the center of the galaxy you have already identified, two smaller foggy clouds, one clearly visible, the other one requiring some effort to discern. Those are our galaxy's two companions, the magellanic clouds, two separate, small, irregular galaxies that are floating not too distant to the milky way's center.
At some point, after reviewing all these parts of the galaxy and its companions, something will happen. You'll "get" it. They will no longer be stains in a painted sphere surrounding you, but you'll suddenly feel stuck to the side of a planet, looking not up but to the side, at the three-dimensional galaxy, edge on. You'll see the magellanic clouds floating above the center of the galaxy, which you'll clearly be able to see now, while you'll feel immersed in the arm of the spiral galaxy the planet is in, noticing how all the stars that surround you are just parts of the same spiral arm.
It is an amazing experience, and you'll never look at the sky and see the same. I did this two times in dark spots in the Andes, and once in the middle of the Pampas. No booze or drugs involved (and I think either of those might make the experience harder to achieve, at least in the same way I experienced it).
It is worth a ticket to the south.

Because of your post, I feel an intense desire to visit the Southern hemisphere now. I love looking up at the sky and reminding myself of how vast all of it is, but it's sometimes hard to see past the "domed ceiling" idea. I'd love to experience this.

This comic made me smile. I love the recall back to this particular style of comic. Haven't seen it in a while.

[Carnildo]

For still photos, this can be done quite easily from an aeroplane.

Take a series of photos out of the window, using some kind of burst mode to get them less than 0.5 seconds apart
Half a second is about 150 m, with a burst you can choose any multiple of this depending on how much depth you want.
Fire up iView and place the two images side by side on your screen.

Squint, fuse the images and enjoy.

Been there, done that, got the crosseye stereopair. 150 meters/0.5 seconds isn't enough: I estimate this one at 500 meters, while this one is somewhere around 800.

[Dellwood]

That said you might find this book interesting: http://www.amazon.co.uk/dp/0465009131. She writes about the experience of perceiving stereopsis after 30 years without.

Fascinating, I was born so cross-eyed I was ostensibly blind (there may have been other issues too, but I never asked my specialist about it). They mostly corrected the crossed eyes with surgery, but they're still misaligned (it was over 25 years ago and apparently my condition was rarely diagnosed back then, for that matter treated, so I imagine they weren't that experienced in that kind of surgery), so I'm in a similar situation to the author, though I don't know if they could correct it any more.

I spent a bunch of time last year reading about stereo vision and talking to ophthalmologists and sadly what worked for her wouldn't work for me - having differing amounts of myopia in each eye as well as misaligned eyes doesn't seem to be solvable without an arrangement of lenses and/or prisms to correct magnification, focus and alignment at the same time.

I'm wondering whether surgery could correct the misalignment, and lenses to correct the myopia...

[martin878]

1000x is not enough difference for humans to see the stars. The distance between the hemispheres, hell, even the difference between summer and winter months is not enough for that. As Douglas Adams said, infinity is staring at the stars and being unable to tell light-years from light-millenia.

Cool idea for clouds, though.

Yea the sky at night would still look flat ... until a airplane flew over, then woah! it's all in my hair!

[AvatarIII]

1000x is not enough difference for humans to see the stars. The distance between the hemispheres, hell, even the difference between summer and winter months is not enough for that. As Douglas Adams said, infinity is staring at the stars and being unable to tell light-years from light-millenia.

Cool idea for clouds, though.

i never thought of that before, but you are right, the difference between summer and winter months is still only 0.003% of a light year, looking at the nearest stars attempting stereoscopy like that would be lke trying to see 3D in something over 3km away, which is about comperable to seeing 3D in clouds unaided.

[Kaetemi]

Okay, I've had this problem before, where people show me one of these, and it's backwards. I.e., the left eye image is on the right, and thus the depth of field is inverted.

However, I've also had people insist that it's not backwards, that it looks fine. So, here's that same image, with the eyes reversed. This one below, by the way, looks "correct" for me - that is, the clouds at the top of the picture are more distant, and the ground slopes away from you. The one above has inverted depth-of-field: the clouds at the top look closer and the ground slopes towards me, like I'm looking up at the ceiling.

I'd love to know if I have some sort of bizarre inverted-depth-of-field eye/brain condition. So, look at the picture above, and this one, and tell me which one looks wrong.

Both are fine, but you have to look at them differently.
Look up cross eyed and straight eyed stereoscopic viewing.

[phelvion]

My first Try:
http://img7.imagebanana.com/img/h7dahisb/wolken.jpg

Distance: 5m

Unfortunately i don't have two foto cameras and the clouds move too fast for perfect 30m-Pics.

[TaylorP]

My first Try:
http://img7.imagebanana.com/img/h7dahisb/wolken.jpg

Distance: 5m

Unfortunately i don't have two foto cameras and the clouds move too fast for perfect 30m-Pics.

It took me a while to get the viewing method to work though. Normally with ones like the golden gate bridge there's something central and defined in the picture, making it easier to get my eyes lined up right to see the 3D. I can't cross my eyes "on demand", so to view the two-panel 3D images I have to stare through the screen and slowly change my focus until the two copies of the central object are brought together. I did eventually get it with the clouds though, and there' definitely some 3D going on there. Good job.

[addams]

For those wanting stellar stereo images check out: http://nzphoto.tripod.com/astro/3dastro/

I've now spent the last half hour googling stereo images instead of school work. XKCD, you keep doing this to me!

http://hubblesite.org/gallery/
The star family gallery. So, pretty.
http://science.nationalgeographic.com/s ... 00x450.jpg
Clouds!
Two D is, just, not enough for some people. Three D is not enough for other people. We need people like that. How else would we ever get anything cool?

We need people that ask; How can we see this differently?
What do you see?

[GenericAnimeBoy]

I've become convinced that National Geographic is a thinly-veiled excuse for people to travel to exotic locations and play with very expensive photographic equipment. Also one of my dream jobs...

[murphlab]

Great comic and beautiful explanation! After reading this, I felt compelled to upload some videos of some hyper-stereoscopic time-lapse experiments I've been working on. I use a pair of canon powershots with CHDK (the open source firmware replacement) installed. I programmed the cameras to shoot at set intervals in sync, using the cameras internal clock as a timer. Therefore I can place the 2 cameras at arbitrary distances, and point them at the same subject. In post I match up the stereo pairs and create time lapse movies.

I shot a handful of test movies around san francisco, with subjects up to several miles away (e.g., downtown sf from the top of dolores park). As a noob on this board I can't link to it, but my blog is the same as my username if anyone's curious.

[WestfW]

Bah; you think too small...
http://science.nasa.gov/science-news/science-at-nasa/2011/18aug_cmemovie/

(interesting timing!)

[GomoX]

Spoiler:

Regarding the stars thing, if you ever wander through the southern hemisphere on a cloudless, dark area during a moonless night, you can certainly experience the depth of space with just a few minutes of concentration. Just lay on your back looking at the sky for a while. Af first it will look flat just as it has always done. But then you'll notice that in the middle of the milky way (which is much more visible and defined in the shouthern sky) there's an area that faintly bulges. That's the center of the galaky, visible behind the closer spirals. You can see a difference between the area with identifiable stars (the closer arms) and the part that's just a shapeless cloud. If you follow the arm to the sides, you'll notice there's a part that also somewhat bulges before becoming fainter. You are looking at the arm along its tangent. If you look up further to the zenith you will notice, slightly above the center of the galaxy you have already identified, two smaller foggy clouds, one clearly visible, the other one requiring some effort to discern. Those are our galaxy's two companions, the magellanic clouds, two separate, small, irregular galaxies that are floating not too distant to the milky way's center.
At some point, after reviewing all these parts of the galaxy and its companions, something will happen. You'll "get" it. They will no longer be stains in a painted sphere surrounding you, but you'll suddenly feel stuck to the side of a planet, looking not up but to the side, at the three-dimensional galaxy, edge on. You'll see the magellanic clouds floating above the center of the galaxy, which you'll clearly be able to see now, while you'll feel immersed in the arm of the spiral galaxy the planet is in, noticing how all the stars that surround you are just parts of the same spiral arm.
It is an amazing experience, and you'll never look at the sky and see the same. I did this two times in dark spots in the Andes, and once in the middle of the Pampas. No booze or drugs involved (and I think either of those might make the experience harder to achieve, at least in the same way I experienced it).
It is worth a ticket to the south.

Because of your post, I feel an intense desire to visit the Southern hemisphere now. I love looking up at the sky and reminding myself of how vast all of it is, but it's sometimes hard to see past the "domed ceiling" idea. I'd love to experience this.

This comic made me smile. I love the recall back to this particular style of comic. Haven't seen it in a while.

I can strongly relate to the comic precisely because I have experienced what the GP describes. In a calm summer night in southern Argentina I could actually (albeit only for brief periods) perceive the depth of the sky instead of the traditional "painted dome" effect. A truly spectacular experience.

This said, I live in the southern hemisphere all year long. I don't really see why you can't do this in the north. Do you not see the Milky Way across the middle of the sky over there?

[lesmith11]

I'd love to know if I have some sort of bizarre inverted-depth-of-field eye/brain condition. So, look at the picture above, and this one, and tell me which one looks wrong.

Most definitely the second image! Not only does it look wrong but it takes a lot of effort to keep my eyes focused on it. Strange...

[lesmith11]

Damn, I guess there are a lot of great 3D images in this thread, but I just can't figure out how to view those side-by-side ones. I've read a lot of guides on how to "get them to work", but still no luck... :\

Can you cross your eyes? Just do that until the two images overlap exactly. I find that they then 'click' into place and no effort is needed to keep the eyes in 3D mode

Edit - on a side note I just remembered when I went to a 3D movie and the lenses were in the wrong way round. It was very uncomfortable viewing Until I decided to wear them upside down

[Yorkist]

About once a month I decide I want to marry you. This one is the first time I want to marry you so bad I actually jumped through all the registration hoops necessary to propose. The Joni Mitchel pushed it right over the edge. Then my kid walked in and reminded me that I'm already married to somebody else. Dammit.

[Cadiac]

Would the original idea in the comic be possible with just one camera and screen for other eye, bare eye for the other, and the observer looking up to the direction where the camera points? That way he could (possibly?) adjust the direction to match by just tilting his head?

[gormster]

Okay, I've had this problem before, where people show me one of these, and it's backwards. I.e., the left eye image is on the right, and thus the depth of field is inverted.

However, I've also had people insist that it's not backwards, that it looks fine. So, here's that same image, with the eyes reversed. This one below, by the way, looks "correct" for me - that is, the clouds at the top of the picture are more distant, and the ground slopes away from you. The one above has inverted depth-of-field: the clouds at the top look closer and the ground slopes towards me, like I'm looking up at the ceiling.

I'd love to know if I have some sort of bizarre inverted-depth-of-field eye/brain condition. So, look at the picture above, and this one, and tell me which one looks wrong.

Both are fine, but you have to look at them differently.
Look up cross eyed and straight eyed stereoscopic viewing.

But the weird thing is, the ones that are purportedly cross-eye are backwards for me, when I use the cross-eye method. (Just to be sure, the cross eye method is the one where you cross your eyes, right? Like with a "Magic Eye" autostereogram?)

Edit: wait, I think the magic eye style ones are actually straight eye. Why would anyone use the cross eye type? Straight eye stereoscopy is almost natural, cross eye is nearly impossibly difficult.

[mooncow]

Edit: wait, I think the magic eye style ones are actually straight eye. Why would anyone use the cross eye type? Straight eye stereoscopy is almost natural, cross eye is nearly impossibly difficult.

OK, first up, different people find different techniques easier or more successful than others. Like you, I find straight-eye much easier than cross-eye: the latter really strains my eyes and I have to work hard to maintain the image. But other people find the cross-eye easier, and some people can't manage the straight-eye at all. That's one of the reasons things like the YouTube 3D video support give you the option to select which style you want. I've seen some magic eye which are straight-eye, but I think most are cross-eye.

Now, for side-by-side images the straight-eye approach hits a limit. If the center-to-center distance is greater than the distance between your eyes, you will not be able to capture the effect, not unless you are able to make your eyeballs diverge. That limits the breadth of visual field you'll ever get with straight-eye side-by-side images. If you want a more immersive full-field effect, you'll have to switch to cross-eye, and just take the strain.

NB this problem does not apply to the magic eye images provided the image period is less than the eye-to-eye distance. Magic eye images in books typically have a period of a few cm. However, an enlarged magic eye picture on a poster would become impossible to view if it required straight-eye. Cross-eye images, magic eye or side-by-side, can always be viewed by placing them at a sensible distance.

mooncow

[mooncow]

Howver, I'm afraid that even the closest stars exhibit an imperceptible (to the naked eye) parallax--only slightly more than roughly 1 arcsecond, even with the image sources separated by 2AU. See also The wikipedia article on the 'Parsec'. Like wobbly said, you would pretty much need to use a computer to enhance the parallax separation.

You could make a stonking 3D image of the moon, though, with a baseline of a few thousand miles. If someone in Europe and someone in North America photograph a full moon at a pre-arranged time when it is visible in both night skies, the two images could then be combined side-by-side. You'd need a bit of work to match colour and light, scale and orientation, but the result could be quite striking, and would make a great wall-poster.

mooncow

[mooncow]

If someone in Europe and someone in North America photograph a full moon at a pre-arranged time when it is visible in both night skies, the two images could then be combined side-by-side.

In fact, since the moon is currently phase-locked, and doesn't change much over time, one person could take two photographs of the moon at different times in the night -- one as it's rising and one as it's setting, say -- and combine them into a 3D image. That might just be worth a try.

mooncow

[mwise]

To those of you lacking 3D depth perception, you can get an idea of the same feature by animating your stereoscopic still frames. So a single image would appear to "rotate" back and forth between the two view points. There are some examples here:

http://izismile.com/2010/05/07/cool_stereoscopic_animated_gifs_30_gifs.html

[senorred]

blag post blag post blag post pleeeeeeeeeeeease!

[RScottMason]

I think this is the zenith of geek poetry. The literary level is obvious: "I stood in my living room at the bottom of an abyss watching mountains drift by", but there is much more on the engineering level, constructing the enabling apparatus, and the scientific level, the cognizant realization of perception. Bravo.

[tom66]

Why even bother with USB / Ethernet / Wifi etc.?

Just use composite video (480/576p) or YCbCr (720p/1080p) cameras. Properly shielded and terminated coax can do 500m+.

[AliceAitch]

Neat idea, beautiful comic. Now someone go take the numbers and actual cloud heights and find a mountain ridge we can use to make it happen.

May I suggest Twin Sisters peak in Rocky Mountain National Park/Roosevelt Forest? There's only about a 15-foot altitude difference between the two main peaks, storms (or at least heavy clouds) are guaranteed nearly every summer afternoon, and the top is close enough to treeline that a couple of fairly fit people could run below treeline fairly quickly. If you get lucky enough to catch the right day, the top gets enveloped in clouds, so you might be able to catch the clouds moving in and around you.

Plus, it's never so crowded that you're going to have people poking their noses in on what you're doing. I've hiked it twice, and even on beautiful days I don't think I've seen more than a dozen people at the summit. (That's pretty rare for a mountaintop in RMNP.)

I think I'd recommend leaving the gear up there during the storm and descending below treeline for the storm itself, though. Lightning strikes are rare up there because people usually don't do thinks like stand around with electronic equipment in their hands. Sure, you're running the risk of your cameras getting zapped, but how awesome would that be?