Re: Rainbows in 3D?

[P3D Larry Berlin <lberlin@xxxxxxxxx>]

>Bob Wier writes:
>
>>clouds and hillsides) Next time I see one I'll understand why the distance
>>is so un-fixable! Rainbows have no parallax that we would be able to see and
>>their location at infinity would be confusing compared to most other cues
>>present. 
>>
>>Larry Berlin
>>
>>Email: lberlin@xxxxxxxxx
>>http://www.sonic.net/~lberlin/
>>http://3dzine.simplenet.com/
>
>I doan wanna be argumentative, but if you look at my slightly hyper
>specimen on my web page, it *clearly* looks closer than the background
>mountains.
>
>http://bobcat.etsu.edu/~wier
>
>My explanation for that is that the apparent origin of the light beams are
at the point of reflection - which in this case was the rainstorm which was
>closer to the view point than the mountains...
>
>--BW


That's not argumentative, it's discussive. : -) I think this is the key,
rainbows originate relative to the refraction/reflection/scattering area but
are still projected relative to the viewer and the sun. Yes, your image has
the rainbow in front of the mountains but both are so far away it's
impossible to determine whether or not the rainbow is at infinity or not.
Since they originate in or near the rainy area and the rain is in front of
the mountains, the rainbow will BOTH appear in front of the mountains AND
when two viewpoints are compared, it would be at the infinity setting in the
stereo shots.

The extra special rainbow I described in my post was less than a mile away
from me and I clearly saw the rain patch and the apparent rainbow in it, but
was unable to get my eyes to agree that the rainbow really originated at
that precise spot. I remember being confused by this since it was so close I
should have been able to *triangulate* it's position with normal depth
perception. Despite it's optical characteristic of infinity, it still
happens in front of objects and features that are closer than infinity,
hence the impossibility of finding the fabled pot of gold that hides under
the ends of it, even when you can identify the apparent end from a distance.

There is a similar effect that I can create in a computer environment. If I
superimpose a stereo-paired object onto another stereo scene, but place the
new object at a displacement of infinity, yet in front of or on top of the
other image which is closer than infinity, confusion of depth placement
results. The effect is similar to the confusion caused by so called
*pseudo-stereo*. The visible depth parallax disagrees with other parts of
the scene and the expected placement.

The only experiment that would prove this would be to use a yard sprinkler
and determine if the rainbow is at infinity. I think that if the scene
includes nearby objects, medium distant objects and infinity, the stereo
pair photos resulting would show an on film deviation for the rainbow that
matches the infinity of the scene, even though the rainbow takes place
closer than the mid-distant objects.

Larry Berlin

Email: lberlin@xxxxxxxxx
http://www.sonic.net/~lberlin/
http://3dzine.simplenet.com/


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