Woody wrote:
> I was testing out some of the Isosurfaces from the documentation and came
> across some thing which I'm not sure if its a bug, a limitation, or so I'm
> just not doing it right.
> 
> The code below renders to the attached image. There seems to be some weird
> normals, shading, or with the general shape. But if I change the viewing
> coordinates to something else like <3,2,5> everything looks fine.
> 
> Can anybody tell me what I'm doing wrong or make any suggestions?
> 
> Image at <web.4712c21a4144865430d4452f0@news.povray.org>
> 
> 
> #include "colors.inc"
> 
> camera {
>  location <2,2,2>
>  look_at <0,0,0>
> }
> 
> isosurface{
>         function{ abs(x)+abs(y)-1}
>         contained_by {box{-1,1}}
>         pigment{color White}
> }
> 
> 
> light_source {
>  <2,2,2>
>  color White
> }

Woody, I received your bug report to the povray.bugreports group, however 
this is *not* a bug.  The messages output by POV-Ray at the time of 
rendering should provide the clue:

"Shutdown Warning: The maximum gradient found was 1.375, but the 
max_gradient of the isosurface was set to 1.100.  The isosurface may 
contain holes!  Adjust max_gradient to get a proper rendering of the 
isosurface."

Therefore, to resolve the issue you're seeing (and as Mark also noticed) 
you have to include a higher max_gradient value in your isosurface, which 
can be done as follows:

isosurface{
   function{ abs(x)+abs(y)-1}
   contained_by {box{-1,1}}
   max_gradient 1.375
   pigment{color White}
}

I'd recommend checking the isosurfaces area in the documentation to read 
more about max_gradient and why this happens as it's something that needs 
to be watched out for.  Note that the higher the max_gradient setting is, 
the slower the isosurface takes to render, which is why the default value 
of max_gradient is set so low.

As an aside, please ensure in the future when submitting possible bugs to 
the povray.bugreports group that you check that the provided SDL is 
syntactically correct, as the SDL you sent with your post contained a 
syntax error that made it difficult to determine whether the problem you 
were having was with the syntax or with something else.

Kind regards,

Lance Birch.

thezone - thezone.firewave.com.au

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