[Lab] Depth Perception

Wed Aug 24 09:45:43 EDT 2011

HackADay has a discussion about this cartoon also.

http://hackaday.com/2011/08/23/we-dont-need-to-brainstorm-projects-xkcd-does-that-for-us/#comments

The last comment was interesting about taking 2 photos of the starry
sky... separated 1/2 year each other, effectively using earths orbit
around the sun to create a huge separation. Still not enough to make
stars 3D, but an interesting experiment regardless! 

Aaron 

On Mon, 22
Aug 2011 16:47:52 -0400, Jason Cobill wrote: 

> Very clever Paul! :)
Tycho Brahe had the same brainwave! Indeed - stereoscopic images are
used in astronomy. Between winter and summer, the earth's orbit takes it
150 million km on either side of the sun, so you get a 300 million km
ocular distance between two photos taken 6 months apart. :)
> 
>
Unfortunately, you're right that even then the depth is pretty
imperceptible except to sensitive instruments.
> From Wikipedia: The
nearest star to the Sun (and thus the star with the largest parallax),
Proxima Centauri, has a parallax of 0.7687 ± 0.0003 arcsec. This angle
is approximately that subtended by an object 2 centimeters in diameter
located 5.3 kilometers away
>
http://en.wikipedia.org/wiki/Parallax#Stellar_parallax [9]
> 
> These
people have gone ahead an exaggerated some illustrations to make the
depth visible to human depth perception.
>
http://www.nightscapes.net/photos/stereo/index.html [10]
> 
> I've seen
some computer renderings of relative star positions in our local cluster
that you can view crosseyed - but I've never seen a "real" photo pair
that's shown depth. Maybe with really distant probes taking star shots
Nasa's got something?
> 
> -Jason Cobill
> 
> On Mon, Aug 22, 2011 at
4:24 PM, Paul & Andrea Mumby wrote:
> 
>> Too bad stars are so far away
that even with several kilometers of stereo separation you likely won't
get depth out of the starfield. Because that would be damn cool... 
>> -
Paul 
>> 
>> On Mon, Aug 22, 2011 at 4:21 PM, Darcy Whyte wrote:
>> 
>>>
Ah, I see, the eyes can can change their alignment to snap on to the 3d
experience automatically. 
>>> So the easiest solution is to just have
the cameras stationary, perhaps converged a couple km out. 
>>> Once
adjusted you can see the clouds go by in 3d. 
>>> I guess time lapse
would be a great way to capture the material. Then you could play it
back whenever you want and the motion would make it cooler. 
>>> But if
you wanted to go real time an pan, you'd need to make sure the pan rates
are well match or it would "un-snap" you from the 3d experience. 
>>> I
bet you could get a nice 3d effect even if the cameras were only like a
few meters apart. 
>>> 
>>> On Mon, Aug 22, 2011 at 4:01 PM, Jason
Cobill wrote: 
>>> 
>>>> Alignment's not too tricky - generally, 3D
movies aim the cameras parallel to eachother and let your brain do the
tricky work of converging the images. They don't need to be exactly
parallel for this to work, and this is the reason some people get wicked
migraines watching Avatar.
>>>> 
>>>> You can get the same effect as the
XKCD experiment (and Avatar) with a highly simplified process:
>>>> -
Find a point on the horizon and take a picture of it.
>>>> - Walk a few
feet.
>>>> - Take a picture aimed at the same point on the horizon
>>>>
- Bring the two images together side-by-side on the computer (preferably
without border lines between them)
>>>> - Cross your eyes really hard
like you're looking at a "magic eye" image, and they'll converge and you
can see your clouds in 3d.
>>>> 
>>>> Or save yourself the effort of
going outside and look at these:
>>>> http://phereo.com/ [1] (Be sure to
click "Mode" and select "Crossed" if you don't want to use special
glasses)
>>>> 
>>>> The technique is really old - I have a number of
friends with collections of stereoscopic images from the mid 1800's! It
was a fun party toy for Victorians.
>>>> You can find out a bit more
here:
>>>> http://en.wikipedia.org/wiki/Stereoscopy [2]
>>>> 
>>>> Also
worth noting that stereo pairs are extensively used in aerial surveys -
a plane takes two photos in succession and the pair can be converged to
get a 3d view. I've often spotted clouds, boats, and even other planes
in high-altitude aerial surveys. I should mention that the effect is a
little less exciting than the XKCD comic paints it to be. Having a pair
of stereo glasses definitely relieves the stress of staring crosswise
and lets you feel a bit more immersed in the image.
>>>> 
>>>> -Jason
Cobill
>>>> 
>>>> _______________________________________________
>>>>
Lab mailing list
>>>> Lab at artengine.ca [3]
>>>>
http://artengine.ca/mailman/listinfo/lab [4]
>>> 
>>>
_______________________________________________
>>> Lab mailing list
>>>
Lab at artengine.ca [6]
>>> http://artengine.ca/mailman/listinfo/lab [7]

Links:
------
[1] http://phereo.com/
[2]
http://en.wikipedia.org/wiki/Stereoscopy
[3] mailto:Lab at artengine.ca
[4]
http://artengine.ca/mailman/listinfo/lab
[5]
mailto:jason.cobill at gmail.com
[6] mailto:Lab at artengine.ca
[7]
http://artengine.ca/mailman/listinfo/lab
[8]
mailto:darcy at siteware.com
[9]
http://en.wikipedia.org/wiki/Parallax#Stellar_parallax
[10]
http://www.nightscapes.net/photos/stereo/index.html
[11]
mailto:themumbys at gmail.com
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://artengine.ca/pipermail/lab/attachments/20110824/a3212a85/attachment.htm>