POV-Ray : Newsgroups : povray.general : Sphere distorted near edge of picture, Server Time
2 Jun 2024 15:26:42 EDT (-0400)
  Sphere distorted near edge of picture, (Message 1 to 5 of 5)  
From: David Harmon
Subject: Sphere distorted near edge of picture,
Date: 18 Aug 2004 20:53:41
Message: <4124f476.517036468@news.povray.org>
There have been many explanations of why a sphere appears
non-circular near the edge of the picture.  The explanation that
makes it perfectly obvious in my mind is this one:

If you look at the shadow of a ball on pavement, the shadow is
an ellipse, unless the sun is directly overhead.  The geometry
of the perspective camera is the same.


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From: Eli
Subject: Re: Sphere distorted near edge of picture,
Date: 19 Aug 2004 13:03:41
Message: <4124dd6d$1@news.povray.org>
look at what happens on the television and in movies. exactly the same thing


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From: Alain
Subject: Re: Sphere distorted near edge of picture,
Date: 19 Aug 2004 16:47:40
Message: <412511ec$1@news.povray.org>
Eli nous apporta ses lumieres ainsi en ce 19/08/2004 13:04... :

>look at what happens on the television and in movies. exactly the same thing 
>
>
>  
>
But, with the movements everywhere, you usualy don't notice it. Also, 
the longer the focal length of the objective, the less it's apparent.

Alain


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From: Harold
Subject: Re: Sphere distorted near edge of picture,
Date: 20 Aug 2004 11:47:26
Message: <41261d0e$1@news.povray.org>
It is also what happens with the human eye, it is our brain
that compensates and perceives objects as undistorted
shapes. It only looks odd in renderings because it is isolated,
out of context, and presented on a two dimensional plane. If
you render the same image from two perspectives as a stereo
image and view it in stereo, it will look realistic rather than
distorted because your brain will fuse the discrepancies
(distortions) of the two images as depth information.

(note: assuming that the angles are within normal human
viewing parameters)

Harolddd

"Eli" <eli### [at] jehoelnet> wrote in message news:4124dd6d$1@news.povray.org...
> look at what happens on the television and in movies. exactly the same
thing
>
>


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From: Rune
Subject: Re: Sphere distorted near edge of picture,
Date: 22 Aug 2004 04:29:05
Message: <41285951@news.povray.org>
Harold wrote:
> It is also what happens with the human eye, it is our brain
> that compensates and perceives objects as undistorted
> shapes.

I don't believe our retina is flat... ;) So whatever distortions appear in
the human eye, it wouldn't be perspective distortions.

> It only looks odd in renderings because it is isolated,
> out of context, and presented on a two dimensional plane.

No, it looks odd because the angle the picture is taken with (or rendered
with) doesn't match the angle that the picture takes up of your field of
view when you're looking at it. If you move your head close to the monitor,
so that the picture takes up an angle of your field of view that is
identical to the angle in the picture, then the distorted view of the
objects will be "distorted back again" and look completely correct. This
however is often not possible in reality, since you'd often have to move
your head ridiculously close to the monitor. But it works in theory.

> If you render the same image from two perspectives as a stereo
> image and view it in stereo, it will look realistic rather than
> distorted because your brain will fuse the discrepancies
> (distortions) of the two images as depth information.

I'm not sure that's necessary.

> (note: assuming that the angles are within normal human
> viewing parameters)

But the whole reason that things look distorted is that the angle of the
image is not within normal viewing parameters - i.e. you have to move your
head very close to the picture to see it in the right angle.

Rune
-- 
3D images and anims, include files, tutorials and more:
rune|vision:  http://runevision.com
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