POV-Ray : Newsgroups : povray.object-collection : The Bright Star Catalogue : Re: The Bright Star Catalogue Server Time
6 Jul 2022 18:25:43 EDT (-0400)
  Re: The Bright Star Catalogue  
From: Mike Horvath
Date: 10 Feb 2018 22:21:56
Message: <5a7fb6d4$1@news.povray.org>
On 2/10/2018 9:44 PM, Bald Eagle wrote:
> Mike Horvath <mik### [at] gmailcom> wrote:
>> I kinda wish there were a POV-Ray object that would be guaranteed to
>> always be 1 pixel big.
> 
> I snipped this out of something I wrote last April, and haven't tested it out
> tonight in a scene all by itself, but it gives you the broad strokes.
> 
> 
> Location is the camera location.
> (So do
> #declare Location = <0, 0, -10>;
> camera { ... location Location  ...}
> )
> Vector is the center of the object you want to be 1 pixel.
> The macro returns the radius of a sphere/cylinder so it is a pixel wide.
> you can work the rest out from there.
> 
> // Minimum radius for solid visibility is (Z/image_width)*Aspect
> // Minimum radius for threshold visibility is (Z/image_width)
> 
> #macro MinRad (Vector)
>     #local Aspect = image_width/image_height;
>     #local Dist = vlength (Vector-Location);
>     #local M = (0.5*Aspect)/tan(radians(Angle/2));
>     #local ZA = Dist/M;
>     #local Rad = (ZA/image_width)*Aspect;
>     Rad
> #end // end macro MinRad
> 
> 

Interesting. Would it work better with a cube oriented to face the 
camera? I suppose the perspective distortion might make the cubes look 
weird if they're toward the edges of the image. But spheres would end up 
looking distorted too.


Mike


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