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I have wandered through the manual looking for this answer and it is
probably an often asked simplistic one. If I take several spheres and have
them placed the same distance from the camera (various distances in the x
and y planes) the spheres furthest away from dead center become distorted or
warped. The further away the more distorted they get. Is this a simple
camera setting issue? My current camera setting is:
camera {
location <0, 0,-6>
look_at <0, 0, 0>
up <0, 1, 0>
right <1, 0, 0>
}
I have tried removing the up and right but it doesn't seem to affect it
much. Is there any way to make the spheres look perfectly round regardless
of position?
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Patrick Dugan wrote:
> I have tried removing the up and right but it doesn't seem to affect it
> much. Is there any way to make the spheres look perfectly round regardless
> of position?
No. This is a perspective principle. Unless the sphere is centered in
the image, it will be distorded. This happens with photographic
cameras, hand drawing, anything. I'll post a shematic explaining
what happens a little later...
The only camera types that act otherwise are orthographic and
fisheye.
You can reduce the effect by playing with the angle and position
of camera, or using ultra_wide_angle.
Fabien.
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I posted the graphical explanation in binaries.images.
Fabien.
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Patrick Dugan <pat### [at] usti com> wrote:
: the spheres furthest away from dead center become distorted or
: warped. The further away the more distorted they get.
[snip]
: Is there any way to make the spheres look perfectly round regardless
: of position?
Why would you want to? If you want a perspective camera then that's
the correct behaviour.
http://www.students.tut.fi/~warp/povVFAQ/misconceptions.html#perspectivespheres
If you really want round spheres, use an orthographic camera. You'll lose
perspective, though.
--
char*i="b[7FK@`3NB6>B:b3O6>:B:b3O6><`3:;8:6f733:>::b?7B>:>^B>C73;S1";
main(_,c,m){for(m=32;c=*i++-49;c&m?puts(""):m)for(_=(
c/4)&7;putchar(m),_--?m:(_=(1<<(c&3))-1,(m^=3)&3););} /*- Warp -*/
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Fabien Mosen wrote:
>
> You can reduce the effect by playing with the angle and position
> of camera, or using ultra_wide_angle.
>
The panoramic camera type will also reduce distortion laterally; AFAIK
it was mainly designed for this purpose.
One thing to keep in mind with the panoramic camera is to place the
"angle" keyword first in the camera block; otherwise it has no effect.
--
Margus Ramst
Personal e-mail: mar### [at] peakeduee
TAG (Team Assistance Group) e-mail: mar### [at] tagpovrayorg
Home page http://www.hot.ee/margusrt
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From: Batronyx
Subject: Re: Dumb question regarding spheres & cameras
Date: 22 Mar 2001 20:51:38
Message: <3abaac2a@news.povray.org>
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The simple answer to your question is to play with the angle keyword.
If I remember correctly the default is 60. IMHO 45 is a better starting
point, but you will have to move your camera back further. This lets you
retain your perspective but minimizes the distortion. It works like a zoom
lens: move further back then reduce the angle to 'zoom' back in.
The reason removing up & right has no effect is partially because you've
specified the defaults, meaning they're still there even though you don't
explicitly say so.
p.s. Try specifying look_at last - even after any transforms - but
especially after the up & right vectors: POV used the information you give
it about up & right to 'automagically' aim it for you with the correct
orientation.
Hope this helps. :)
bat### [at] cadronhsacom
Patrick Dugan wrote in message <3ab905fd$1@news.povray.org>...
>I have wandered through the manual looking for this answer and it is
>probably an often asked simplistic one. If I take several spheres and have
>them placed the same distance from the camera (various distances in the x
>and y planes) the spheres furthest away from dead center become distorted
or
>warped. The further away the more distorted they get. Is this a simple
>camera setting issue? My current camera setting is:
>
>camera {
> location <0, 0,-6>
> look_at <0, 0, 0>
> up <0, 1, 0>
> right <1, 0, 0>
>}
>
>I have tried removing the up and right but it doesn't seem to affect it
>much. Is there any way to make the spheres look perfectly round regardless
>of position?
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Issue has been resolved. Although I read a lot of feedback the problem was
due to rendering resolution. The distortion came from rendering the image
1024x768. There the spheres are warped (and incorrectly so to my eyes) so I
tried rendering the image "square" at 1024x1024. Voila! The spheres are
now correctly shaped and the perspective is normal to my eyeballs.
Okay so I'm a moron....
"Patrick Dugan" <pat### [at] usticom> wrote in message
news:3ab905fd$1@news.povray.org...
> I have wandered through the manual looking for this answer and it is
> probably an often asked simplistic one. If I take several spheres and
have
> them placed the same distance from the camera (various distances in the x
> and y planes) the spheres furthest away from dead center become distorted
or
> warped. The further away the more distorted they get. Is this a simple
> camera setting issue? My current camera setting is:
>
> camera {
> location <0, 0,-6>
> look_at <0, 0, 0>
> up <0, 1, 0>
> right <1, 0, 0>
> }
>
> I have tried removing the up and right but it doesn't seem to affect it
> much. Is there any way to make the spheres look perfectly round
regardless
> of position?
>
>
>
>
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"Patrick Dugan" <pat### [at] usticom> wrote in message
news:3abb8678$1@news.povray.org...
>
> Okay so I'm a moron....
>
And so are we (for not guessing what the real problem was). The moral of
this story is always post an image to binaries....
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From: Margus Ramst
Subject: Re: Dumb question regarding spheres & cameras
Date: 23 Mar 2001 17:19:15
Message: <3abbcbe3@news.povray.org>
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"Patrick Dugan" <pat### [at] usticom> wrote:
> Issue has been resolved. Although I read a lot of feedback the problem
> was due to rendering resolution. The distortion came from rendering the
> image 1024x768. There the spheres are warped (and incorrectly so to my
> eyes) so I tried rendering the image "square" at 1024x1024. Voila! The
> spheres are now correctly shaped and the perspective is normal to my
> eyeballs.
Are you sure?
With the standard perspective camera, objects are *always* stretched towards
the edges of the image, no matter what your aspect ratio. Near the sides of
the image, they are stretched laterally. If you simply changed the aspect
ratio of the image without modifying the up and right vectors, the image
would be stretched vertically (try it: for example render skyvase.pov with +h300
+w100). This might seem to compensate for the lateral stretching near the
image sides, but the center and upper & lower edges of the image would
still appear distorted.
--
Margus Ramst
Personal e-mail: mar### [at] peakeduee
TAG (Team Assistance Group) e-mail: mar### [at] tagpovrayorg
Home page http://www.hot.ee/margusrt
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More than sure. The aspect ratio distorted the spheres and setting it back
to square made a major difference. I guess I will create an example but one
way to really see it is to render in a mode like 1024 x 10. Obviously the
spheres will be extremely warped due to the aspect ratio. 1024 x 768 isn't
as bad but is still warped. 1024 x 1024 gives the correct image. I'll try
posting an example tonight in the binaries.images section.
"Margus Ramst" <mar### [at] peakeduee> wrote in message
news:3abbcbe3@news.povray.org...
> "Patrick Dugan" <pat### [at] usticom> wrote:
>
> > Issue has been resolved. Although I read a lot of feedback the problem
> > was due to rendering resolution. The distortion came from rendering the
> > image 1024x768. There the spheres are warped (and incorrectly so to my
> > eyes) so I tried rendering the image "square" at 1024x1024. Voila! The
> > spheres are now correctly shaped and the perspective is normal to my
> > eyeballs.
>
> Are you sure?
> With the standard perspective camera, objects are *always* stretched
towards
> the edges of the image, no matter what your aspect ratio. Near the sides
of
> the image, they are stretched laterally. If you simply changed the aspect
> ratio of the image without modifying the up and right vectors, the image
> would be stretched vertically (try it: for example render skyvase.pov with
+h300
> +w100). This might seem to compensate for the lateral stretching near the
> image sides, but the center and upper & lower edges of the image would
> still appear distorted.
>
> --
> Margus Ramst
>
> Personal e-mail: mar### [at] peakeduee
> TAG (Team Assistance Group) e-mail: mar### [at] tagpovrayorg
> Home page http://www.hot.ee/margusrt
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