POV-Ray : Newsgroups : povray.advanced-users : Strange media artefact : Re: Strange media artefact Server Time
19 Jun 2021 17:34:40 EDT (-0400)
  Re: Strange media artefact  
From: Alain Martel
Date: 11 Feb 2021 10:59:04
Message: <60255448$1@news.povray.org>
Le 2021-02-08 à 14:38, Bald Eagle a écrit :
> 
> While working out some media stuff for Mike, I ran a a quick media test to just
> make sure I had the standard part working, and I got some odd results.
> 
> Perhaps someone could render this and tell me why the center gives me a nice x
> gradient, but off to the sides I get those weird fans / lines.
> 
> (Alain, fyi:  the syntax is simply "method 3", not "sampling_method 3")
> 
> 
> #version 3.8;
> global_settings {assumed_gamma 1.0 }
> 
> camera {
>   location <0, 8, -10>
>   //location <0, 10, 3>
>   right x*image_width/image_height
>   up y
>   look_at <0, 0, 0>
> }
> 
> light_source {<0, 50, -1> rgb 1}
> 
> sky_sphere {pigment {rgb <1, 1, 1>}}
> 
> 
> box {<-10, -1, -5>, <10, 1, 5>
>   pigment {rgbt 1}
>   hollow
>   interior {
>    media {
>     absorption <1, 1, 1>
>     //emission <1, 0.2, -0.6>*0.9
>     //scattering{ 1, <1,1,1>
>     //extinction  2.0
>     method 3
>     intervals 1 //DO NOT increase !
>     samples 10, 50
>     density {
>      gradient x
>      color_map {
>       [0.0 rgb 0.0]//border
>       //[0.5 rgb 0.1]
>       [1.0 rgb 1.0]//center
>      } // end color_map
>     } // end density
>    } // end media
>   } // end interior
> 
> } // end box
> 
> 

It's a case of not enough samples. In my test, I needed to increase all 
the way to samples 50 to completely get rid of those lines.

In this case, you don't need the color_map as it exactly match what the 
gradient pattern already give you.

Instead of using a sky_sphere with a solid pigment, you should use 
background{ rgb 1}. A sky_sphere is for when you want a pattern as your 
background.

With the current background and media type, you don't need any light.


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