>> Wouldn't it depend on the resolution of the images and the size of the 
>> objects in question?
> 
> No, it's a simple fact that with only two photos there is never enough 
> information to make a 3D model

I don't think that's true.

> and be sure it is correct.

Oh, right. That's slightly different.

> Your brain 
> always has to add in unseen or assumed details, which most of the time 
> are believably correct, but I guess this is extremely hard for a 
> computer to do (as it's based on your experiences etc).

I think the primary thing that stereoscopic vision gives you is depth 
perception. Using it, you can tell, with reasonable accuracy, how far 
away a given surface is. (Seems to be more accurate for near objects; 
very distant ones like clouds tend to look "flat".)

I would have thought it ought to be possible to take a stereo photograph 
and construct a kind of texture-mapped height field from that. I agree 
that if you take a picture of a cup, the computer doesn't really stand a 
chance of figuring out what the *back* of the cup looks like.

Now, if you take lots of pictures from lots of different angles... well, 
I'm guessing the hard part is going to be figuring out how the images 
"fix together".

Post a reply to this message

On 11/30/2009 5:28 AM, Invisible wrote:
> I think the primary thing that stereoscopic vision gives you is depth
> perception. Using it, you can tell, with reasonable accuracy, how far
> away a given surface is. (Seems to be more accurate for near objects;
> very distant ones like clouds tend to look "flat".)

Stereoscopic vision allows you to triangulate an object's position, just 
like a surveyor can determine an object's position by forming a triangle 
between an object and two reference points.

--
Michael Horvath
mik### [at] gmailcom
http://isometricland.com

Post a reply to this message

I thought this video was fitting:

http://www.youtube.com/watch?v=3609OtM138c

He talks about "one day" people being able to create 3D models from all 
the pics lying around the net of him. I guess that day has finally come 
true!!

:)


--
Michael Horvath
mik### [at] gmailcom
http://isometricland.com

Post a reply to this message

SharkD wrote:

> He talks about "one day" people being able to create 3D models from all 
> the pics lying around the net of him. I guess that day has finally come 
> true!!
> 
> :)

For some reason, the first thought that popped into my head was "OMG - 
the goatse guy! NOOOOOO!!!"

Post a reply to this message

Invisible wrote:
>>> Wouldn't it depend on the resolution of the images and the size of
>>> the objects in question?
>>
>> No, it's a simple fact that with only two photos there is never enough
>> information to make a 3D model
> 
> I don't think that's true.
> 

http://www.youtube.com/watch?v=MikG05MV3GU&feature=related

Take any two frames, and tell me if the blue or white side is convex.

> I would have thought it ought to be possible to take a stereo photograph
> and construct a kind of texture-mapped height field from that. I agree
> that if you take a picture of a cup, the computer doesn't really stand a
> chance of figuring out what the *back* of the cup looks like.

Stereo photographs suffer from one problem that the eyes do not appear
to, focus. The brain and eye do all the 'number crunching' to preserve
the information and make you think everything is still in focus,
allowing your eyes to shift and pick up other details. Which also helps
with distance recognition.

To do that with a camera, you would need a ton of pictures or a very
small aperture. The first benefits in adding extra ranger information,
the latter only helps in the amount of data to be processed.

From a picture of a cup, shot edge on in full diffuse lighting, I doubt
a computer could even tell you if it was round, square, or any other
convex or concave shape. Not from just two pictures.

> Now, if you take lots of pictures from lots of different angles... well,
> I'm guessing the hard part is going to be figuring out how the images
> "fix together".

Which is what makes this software look kinda neat. Not only is it doing
that work, but it appears to be doing it in real time.

Post a reply to this message

Invisible wrote:
> I think the primary thing that stereoscopic vision gives you is depth 
> perception. 

That and the ability to see around close-by objects.

-- 
Darren New, San Diego CA, USA (PST)
   Human nature dictates that toothpaste tubes spend
   much longer being almost empty than almost full.

Post a reply to this message

Invisible <voi### [at] devnull> wrote:
> I think the primary thing that stereoscopic vision gives you is depth 
> perception.

  The lack of depth perception of people who are blind on one eye has been
greatly exaggerated. People with only one seeing eye have a surprisingly
good depth perception.

  And that doesn't take years. It takes just a minute or so. You can test
it yourself, and it's actually quite awesome. For instance, watch a 3D game
of even a movie with one eye (cover your other eye with something). In a
few tens of seconds you will start seeing the game with depth perception.
It will start looking truly three-dimensional (not *exactly* as well as
a real three-dimensional scene looked with both eyes, but almost).

  The reason is that the brain is really good at compensating for the lack
of stereoscopic view, and will start to use secondary clues to form a
perception of depth.

-- 
                                                          - Warp

Post a reply to this message

>> I think the primary thing that stereoscopic vision gives you is depth 
>> perception.
> 
>   The lack of depth perception of people who are blind on one eye has been
> greatly exaggerated. People with only one seeing eye have a surprisingly
> good depth perception.

Shut one eye. The world doesn't really look any different.

Now try and pick something up.

Oh. OK, my hand is actually nowhere near. I guess depth perception *is* 
important after all.

(Even more fun is trying to drive with one eye shut. I strongly 
recommend that you *never*, ever try this!)

On the other hand, if you're looking at a *moving* picture, you still 
have parallax to aid you. Not to mention that many types of surfaces 
have patterns that are predictable enough to allow you to guess how far 
away they are.

(It is notable, actually, that certain natural objects possess such 
scale-invarience that you can't reliably tell how big they are. Rocks 
work well in this regard...)

Post a reply to this message

Invisible <voi### [at] devnull> wrote:
> >> I think the primary thing that stereoscopic vision gives you is depth 
> >> perception.
> > 
> >   The lack of depth perception of people who are blind on one eye has been
> > greatly exaggerated. People with only one seeing eye have a surprisingly
> > good depth perception.

> Shut one eye. The world doesn't really look any different.

> Now try and pick something up.

  Yes, because a few seconds will certainly be enough for your brain to
adjust.

  Did you try what I suggested?

-- 
                                                          - Warp

Post a reply to this message

>>>   The lack of depth perception of people who are blind on one eye has been
>>> greatly exaggerated. People with only one seeing eye have a surprisingly
>>> good depth perception.
> 
>> Shut one eye. The world doesn't really look any different.
> 
>> Now try and pick something up.
> 
>   Yes, because a few seconds will certainly be enough for your brain to
> adjust.
> 
>   Did you try what I suggested?

I haven't tried doing this over an extended time period, no. However, if 
it's anything like other human senses, I would imagine the brain manages 
to compensate to at least some degree after a while...

Post a reply to this message