"Warp" <war### [at] tagpovrayorg> wrote in message news:3fa7a09a@news.povray.org...
> Christoph Hormann <chr### [at] gmxde> wrote:
> > Actually you should use sqrt() instead of pow(,0.5).
>
>   How about simply squaring the radius (R*R) instead of using the slow
> sqrt() function?-)

He's got a point.... in which case it would make sense to declare R as the
square of whatever value you want to use?

So, Chris's example becomes:

#declare R=2*2;
#declare FSphere=function {(x*x+y*y+z*z) - R}

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Tom Melly <tom### [at] tomandlucouk> wrote:
> #declare R=2*2;
> #declare FSphere=function {(x*x+y*y+z*z) - R}

  Having the radius as parameter has certain advantages, though.
For instance, the radius does not have to be constant thorough the
entire surface of the sphere... :)

  Example:

#declare FSphere = function(x,y,z,R) { (x*x+y*y+z*z) - R*R }

isosurface
{ function { FSphere(x,y,z, 2-.5*f_noise3d(x*5,y*5,z*5)) }
  ...
}

-- 
plane{-x+y,-1pigment{bozo color_map{[0rgb x][1rgb x+y]}turbulence 1}}
sphere{0,2pigment{rgbt 1}interior{media{emission 1density{spherical
density_map{[0rgb 0][.5rgb<1,.5>][1rgb 1]}turbulence.9}}}scale
<1,1,3>hollow}text{ttf"timrom""Warp".1,0translate<-1,-.1,2>}//  - Warp -

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Warp wrote:
> 
>   How about simply squaring the radius (R*R) instead of using the slow
> sqrt() function?-)

Because that function would have a non-constant gradient.  With the (way 
too large) container box{-5,5} you need quite a high max_gradient to 
correctly render it -> it will be slower than with sqrt().

Of course using the internal function f_sphere() would be even faster.

Christoph

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