In article <39621861@news.povray.org>, "hall" 
<tre### [at] ww-interlinknet> wrote:

I believe your problem is here...

> #declare a = function { x*x+y*y+z*z }

and here...
>  function {a(x,y,z)}
>  contained_by{sphere {0,4}}

Your function "a" increases exponentially from < 0, 0, 0>, and the 
contained_by object goes far outside the actual surface, so a high 
max_gradient is required, and calculation is slower. Try using 
"sqrt(sqr(x), sqr(y), sqr(z))". The sqr() should be a little faster than 
x*x, and the sqrt() will make it a linear increase.

-- 
Christopher James Huff - Personal e-mail: chr### [at] maccom
TAG(Technical Assistance Group) e-mail: chr### [at] tagpovrayorg
Personal Web page: http://homepage.mac.com/chrishuff/
TAG Web page: http://tag.povray.org/

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