POV-Ray : Newsgroups : povray.newusers : possible to cast single rays? Server Time
4 Nov 2024 13:00:19 EST (-0500)
  possible to cast single rays? (Message 1 to 4 of 4)  
From: simon shannon
Subject: possible to cast single rays?
Date: 23 Jun 2003 05:30:01
Message: <web.3ef6c830ae88514ab7fd4d090@news.povray.org>
Dear All,

    I have a height field with an image draped over it (image_map).
Instead of generating an image of the whole scene, I would just like
to know the value of, say 1000 specified pixels taken from a 512x384
view and write them out to a file. Is that possible?

      -Simon Shannon


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From: JC (Exether)
Subject: Re: possible to cast single rays?
Date: 23 Jun 2003 08:02:13
Message: <3EF6EC43.3060300@spam.fr>
I'm not sure that I understand what you want to get, but my first idea 
is that if you want to see just a thousand pixels you can do a 31x31 
render or something like this.
Apart from that, I don't think you can select pixels to be rendered from 
a pool of 512x384 pixels, you would e able to do that by specifying 
spans that you want to render in the image, but that would mean to redo 
the parsing of the scene each time.

JC

simon shannon wrote:
> Dear All,
> 
>     I have a height field with an image draped over it (image_map).
> Instead of generating an image of the whole scene, I would just like
> to know the value of, say 1000 specified pixels taken from a 512x384
> view and write them out to a file. Is that possible?
> 
>       -Simon Shannon
>


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From: Tom Galvin
Subject: Re: possible to cast single rays?
Date: 23 Jun 2003 10:02:18
Message: <Xns93A36604A8E79tomatimporg@204.213.191.226>
"simon shannon" <ssh### [at] tazqinetiqcom> wrote in 
news:web.3ef6c830ae88514ab7fd4d090@news.povray.org:

> 
> Instead of generating an image of the whole scene, I would just like
> to know the value of, say 1000 specified pixels taken from a 512x384
> view and write them out to a file. Is that possible?
> 
> 
> 

Yes.

5.2.2.1.2  Partial Output Options

If you are using the Windows client, as a shortcut you can highlight a 
section of the render window with your mouse for the same effect.


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From: Mike Williams
Subject: Re: possible to cast single rays?
Date: 23 Jun 2003 13:41:34
Message: <ZVUabDAalz9+Ew60@econym.demon.co.uk>
Wasn't it simon shannon who wrote:
>
>Dear All,
>
>    I have a height field with an image draped over it (image_map).
>Instead of generating an image of the whole scene, I would just like
>to know the value of, say 1000 specified pixels taken from a 512x384
>view and write them out to a file. Is that possible?

You can use trace() and eval_pigment() to achieve something like the
equivalent of casting an individual ray. Trace() will tell you the point
where your ray intersects the object. Eval_pigment() will tell you the
colour of the pigment at that point. 

You'll also need to use #fopen and #write() to write the data to a file.

-- 
Mike Williams
Gentleman of Leisure


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