Christopher James Huff wrote:
> In article <3f985f2b$1@news.povray.org>,
>  "Tom A." <met### [at] yahoocom> wrote:
> 
> 
>>I was playing with functions, trying to learn about isosurfaces, when I 
>>found something that looked like a "black hole".  But I noticed what 
>>looked like some strange shadows or reflections on it, and I cleaned up 
>>my code and have some questions on it.
> 
> 
> This sounds like typical artifacts of the isosurface intersection 
> solving algorithm. If so, it has nothing directly to do with the log() 
> function, it is caused by your function having too high of a gradient.
> Using higher quality settings (mainly a higher max_gradient) will reduce 
> or eliminate these artifacts.

Thank you, and the the others who answered my questions.


> 
> 
> 
>>Can the ?: (conditional) operator be used in a function?
> 
> 
> No. The select() function gives the same functionality, however.
> http://povray.org/documentation/view/137/#s06_01_03_06
> 
> 
> 
>>Can vlength() be used in a function?  (It kept complaining about the "<" 
>>symbol on the vector I passed it).
> 
> 
> No. Neither can any other vector functions. User defined functions have 
> no concept of "vectors". The only way you can get a vector value from 
> one is to use a transform, pigment, or spline function, and you can't 
> perform mathematical operations on vectors within a function.
> 
> A full listing of what you can use in functions is here:
> http://povray.org/documentation/view/140/
> 

Tom A.

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