Wasn't it Tom Melly who wrote:
>"ingo" <ing### [at] homenl> wrote in message
>news:Xns### [at] povrayorg...
>> in news:3ba0c9b8@news.povray.org Tom Melly wrote:
>>
>> > Although correct, wouldn't this be better as:
>> > [...]
>> >   function  {y - FBozo(x,0,z).gray }
>> >
>>
>> Why?
>>
>
>Because, and I may be doing something stupid, the following does not actually
>render anything as far as I can see...
>
>#declare fn_floor= function{pigment{bozo color_map{[0 rgb 0][1 rgb 1]}}}
>isosurface {
>  function {fn_floor(x,y,z).gray}
>  max_gradient 7
>  contained_by {box{<-10,-10,-10>,<10,10,10>}}
>  accuracy 0.1
>  evaluate 1, 1.2, 0.99
>  pigment{rgb 1}
>  finish{ambient 1}
>
>}


Because, of course, the specified pigment takes values that are greater
than zero everywhere (using the new default noise_generator settings -
bozo using the old noise algorithm had plateaus at zero) and the default
threshold is zero. The surface only exists at points where the function
is equal to the threshold, and that doesn't happen.

An alternative fix would be to specify something like "threshold 0.5",
but that's a bit of a boring surface.

-- 
Mike Williams
Gentleman of Leisure

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