Mike Williams wrote:

> Wasn't it Bill Hails who wrote:
> 
>>http://thyme.homelinux.net/IsoCylinder.html
> 
> One thing that immediately jumps out as being a bit dodgy is the fact
> that
> 
>         (CyFn(x, y, z).gray - 0.5) * Intensity
> 
> can be negative for some points on some pigment patterns. At such points
> the isosurface will be slightly larger than the specified Radius and can
> cause a thin sliver of surface fall outside the contained_by box.
> 
> I can't quite see how that would cause exactly the effect that you
> showed in the image you posted, but you  could try doing something like
> this to force the box to be big enough to contain the bits that stand
> proud of the surface
> 
>         #declare Box_Width = Radius + sqrt(Intensity*0.5);
>         contained_by {
>             box {
>                 <-Box_Width, 0, -Box_Width>,
>                 <Box_Width, Height, Box_Width>
>             }
>         }
> 
> Or, more simply, ensure that your surface fits inside the box by not
> subtracting 0.5 from the pigment
> 
>         (CyFn(x, y, z).gray) * Intensity
> 

You're right as usual. I was subtracting 0.5 so that the "average"
surface would be coincident with the unperturbed cylinder. I'll
increase the box dimensions.

-- 
Bill Hails
http://thyme.homelinux.net/

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