gregjohn wrote:
> It took me 13 years of povving to understand the camera. That is, to come up
> with the code for a box which exactly fills the screen, regardless of camera
> angle/ distance and image aspect ratio.

I don't see what the difficulty is. It's as simple as this:

camera
{
	location	<0,0,-4>
	direction	<0,0,+4>	// reciprocal of location
	up		y
	right		x*image_width/image_height
}

// polygon centered on the origin with sides of length 1
polygon
{
	4, <-1/2,-1/2>, <-1/2,+1/2>, <+1/2,+1/2>, <+1/2,-1/2>
	pigment {color Red}	
}

The trick here is to not use the angle and look_at keywords. In this 
case, they're more trouble than they're worth. Also, if you omit the 
image_width/image_height stuff, then it fills the viewport *exactly*, 
regardless of the aspect ratio.

-Mike

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SharkD schrieb:
> gregjohn wrote:
>> It took me 13 years of povving to understand the camera. That is, to 
>> come up
>> with the code for a box which exactly fills the screen, regardless of 
>> camera
>> angle/ distance and image aspect ratio.
> 
> I don't see what the difficulty is. It's as simple as this:
> 
> ...
> 
> The trick here is to not use the angle and look_at keywords. In this 
> case, they're more trouble than they're worth. Also, if you omit the 
> image_width/image_height stuff, then it fills the viewport *exactly*, 
> regardless of the aspect ratio.

What you're doing is designing camera parameters so that a certain 
"friendly" box fills the entire screen.

The OP's challenge, however, was quite different: From a given arbitrary 
(potentially "unfriendly") camera perspective, compute parameters for a 
box to fill the screen (possibly to overlay a border, signature or 
whatever onto the image).

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"clipka" <ano### [at] anonymousorg> wrote in message 
news:4a80d86e$1@news.povray.org...
> SharkD schrieb:
>> gregjohn wrote:
>>> It took me 13 years of povving to understand the camera. That is, to 
>>> come up
>>> with the code for a box which exactly fills the screen, regardless of 
>>> camera
>>> angle/ distance and image aspect ratio.
>>
>> I don't see what the difficulty is. It's as simple as this:
>>
>> ...
>>
>> The trick here is to not use the angle and look_at keywords. In this 
>> case, they're more trouble than they're worth. Also, if you omit the 
>> image_width/image_height stuff, then it fills the viewport *exactly*, 
>> regardless of the aspect ratio.
>
> What you're doing is designing camera parameters so that a certain 
> "friendly" box fills the entire screen.
>
> The OP's challenge, however, was quite different: From a given arbitrary 
> (potentially "unfriendly") camera perspective, compute parameters for a 
> box to fill the screen (possibly to overlay a border, signature or 
> whatever onto the image).

isn't that exactly why screen.inc was made?

cu!
-- 
#macro G(b,e)b+(e-b)*C/50#end#macro _(b,e,k,l)#local C=0;#while(C<50)
sphere{G(b,e)+3*z.1pigment{rgb G(k,l)}finish{ambient 1}}#local C=C+1;
#end#end _(y-x,y,x,x+y)_(y,-x-y,x+y,y)_(-x-y,-y,y,y+z)_(-y,y,y+z,x+y)
_(0x+y.5+y/2x)_(0x-y.5+y/2x)            // ZK http://www.povplace.com

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