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From: Tom Melly
Subject: Camera look_at question
Date: 21 Jan 2004 11:26:56
Message: <400ea850@news.povray.org>
I've never really understood how to use all the different camera option - just
the basics, position, look_at, up and right (and the occasional foray into
orthographic), so if this question is bleedin' obvious, I humbly apologise.

Is there a way to make the look_at point not the centre of the image? Obviously,
I could acheive a similiar result by cropping the image once it's rendered, but
then I'm wasting time rendering parts of the image I don't intend to keep.

-- 
#macro A(V,B,C,R)#while(B-256)#if(V-128/B>=0)sphere{0,.5translate<C-4R-1,9>
pigment{rgb<1-C/8R/2C/8>}}#local V=V-128/B;#end#local B=B*2;#local C=C+1;#
end#end A(234,1,0,2)A(85,1,0,1)A(81,1,0,0)light_source{-5 1}//Tom Melly


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From: Slime
Subject: Re: Camera look_at question
Date: 21 Jan 2004 13:59:44
Message: <400ecc20$1@news.povray.org>
> Is there a way to make the look_at point not the centre of the image?
Obviously,
> I could acheive a similiar result by cropping the image once it's
rendered, but
> then I'm wasting time rendering parts of the image I don't intend to keep.

My include file zoomin.inc ( http://www.slimeland.com/misc/zoomin.inc )
makes this relatively easy to do. However, I'm not certain that it's exactly
what you want: looking in a direction A and taking a portion of an image
which is looking in direction B does not create the same effect.

 - Slime
 [ http://www.slimeland.com/ ]


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From: Nicolas Calimet
Subject: Re: Camera look_at question
Date: 21 Jan 2004 14:30:13
Message: <400ed345$1@news.povray.org>
> Is there a way to make the look_at point not the centre of the image? Obviously,
> I could acheive a similiar result by cropping the image once it's rendered, but
> then I'm wasting time rendering parts of the image I don't intend to keep.

	Why not to use the +sr +er +sc +ec switches ?

	It effectively crops the image by rendering the part you are interested in,
which does not need to be centered around the whole image center (pan effect).
The missing portions of the image (black areas) still need to be manually removed
in your favorite image editor (usual select/copy/paste in new image).

	- NC


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From: Tim Nikias v2 0
Subject: Re: Camera look_at question
Date: 21 Jan 2004 15:03:08
Message: <400edafc@news.povray.org>
> Is there a way to make the look_at point not the centre of the image?
Obviously,
> I could acheive a similiar result by cropping the image once it's
rendered, but
> then I'm wasting time rendering parts of the image I don't intend to keep.

Well, the point of look_at is to provide a center on which the image
focusses. For the actual camera focus, focal-blur using a different
focal_point might achieve what you're after, since it can effectively blur
the look_at position (given the right scene).

Aside of that, how about moving look_at somewhere else? I don't get why
you'd want the camera to behave irrationally and look at something different
than look_at. :-S

Regards,
Tim

-- 
"Tim Nikias v2.0"
Homepage: <http://www.nolights.de>
Email: tim.nikias (@) nolights.de


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From: Jim Charter
Subject: Re: Camera look_at question
Date: 21 Jan 2004 15:18:47
Message: <400edea7@news.povray.org>
Tom Melly wrote:
> I've never really understood how to use all the different camera option - just
> the basics, position, look_at, up and right (and the occasional foray into
> orthographic), so if this question is bleedin' obvious, I humbly apologise.
> 
> Is there a way to make the look_at point not the centre of the image? Obviously,
> I could acheive a similiar result by cropping the image once it's rendered, but
> then I'm wasting time rendering parts of the image I don't intend to keep.
> 
Whatever you intend to keep has a center, doesn't it?


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From: Severi Salminen
Subject: Re: Camera look_at question
Date: 21 Jan 2004 17:29:14
Message: <400efd3a$1@news.povray.org>
> Well, the point of look_at is to provide a center on which the image
> focusses. For the actual camera focus, focal-blur using a different
> focal_point might achieve what you're after, since it can effectively blur
> the look_at position (given the right scene).
>
> Aside of that, how about moving look_at somewhere else? I don't get why
> you'd want the camera to behave irrationally and look at something
different
> than look_at. :-S

For the same reason as large format cameras have the ability to move the
film plane (shifting) so that the center axis of the lens does not point at
the center of the film. This allows quite interesting (and many times very
useful) perspective corrections/alterations. It is not about focal blur. I
think this is what Tom wants to accomplish? Basically this can be
accomplished by rendering only a portion of a larger image, but it is an
"ugly" way to do it.

POV-Ray lacks a couple more or less useful things such as defining the
direction focus plane when using focal blur, the shifting (as above) etc.
These would be useful things to add at some point.

Severi Salminen


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From: Tom Melly
Subject: Re: Camera look_at question
Date: 22 Jan 2004 04:12:35
Message: <400f9403$1@news.povray.org>
"Nicolas Calimet" <pov### [at] freefr> wrote in message
news:400ed345$1@news.povray.org...
> > Is there a way to make the look_at point not the centre of the image?
Obviously,
> > I could acheive a similiar result by cropping the image once it's rendered,
but
> > then I'm wasting time rendering parts of the image I don't intend to keep.
>
> Why not to use the +sr +er +sc +ec switches ?
>

An obvious solution that completely eluded me. Doh!


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From: Tom Melly
Subject: Re: Camera look_at question
Date: 22 Jan 2004 04:34:58
Message: <400f9942$1@news.povray.org>
"Tim Nikias v2.0" <tim.nikias (@) nolights.de> wrote in message
news:400edafc@news.povray.org...
>
> Well, the point of look_at is to provide a center on which the image
> focusses. For the actual camera focus, focal-blur using a different
> focal_point might achieve what you're after, since it can effectively blur
> the look_at position (given the right scene).

The effect I'm after isn't really anything to do with focal-blur.

> Aside of that, how about moving look_at somewhere else? I don't get why
> you'd want the camera to behave irrationally and look at something different
> than look_at. :-S

To be honest, I'm not *entirely* sure myself - except to say that I want the
subject of my image to not be in the centre of the image, and not distorted by
being elsewhere. I've posted an image to binaries.images (look_at image) to show
the effect (note the distorted/undistorted sphere - heh, well hard to miss it;).


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From: Philippe Debar
Subject: Re: Camera look_at question
Date: 22 Jan 2004 06:09:02
Message: <400faf4e@news.povray.org>
You could check POV-Ray 3.5/scenes/camera/shear.pov

Don't forget to disable vista buffers (-uv)

Otherwise, partial output is the way to go.

I hope this helps,

Povingly,

Philippe


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From: Jim Charter
Subject: Re: Camera look_at question
Date: 22 Jan 2004 09:06:40
Message: <400fd8f0$1@news.povray.org>
Severi Salminen wrote:
>>Well, the point of look_at is to provide a center on which the image
>>focusses. For the actual camera focus, focal-blur using a different
>>focal_point might achieve what you're after, since it can effectively blur
>>the look_at position (given the right scene).
>>
>>Aside of that, how about moving look_at somewhere else? I don't get why
>>you'd want the camera to behave irrationally and look at something
> 
> different
> 
>>than look_at. :-S
> 
> 
> For the same reason as large format cameras have the ability to move the
> film plane (shifting) so that the center axis of the lens does not point at
> the center of the film. This allows quite interesting (and many times very
> useful) perspective corrections/alterations. It is not about focal blur. I
> think this is what Tom wants to accomplish? Basically this can be
> accomplished by rendering only a portion of a larger image, but it is an
> "ugly" way to do it.
> 
> POV-Ray lacks a couple more or less useful things such as defining the
> direction focus plane when using focal blur, the shifting (as above) etc.
> These would be useful things to add at some point.
> 
> Severi Salminen
> 
Ah I get it now.  Divorse the lens perspective from the frame of the 
picture.


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