"lars petter" <lar### [at] higno> wrote in message
news:4030e7fc$1@news.povray.org...

> Quartic parabola - a 4th degree polynomial (has two bumps at the bottom)
> that has been swept around the z axis. The equation is:
> 0.1 x^4 - x^2 - y^2 - z^2 + 0.9 = 0
>
> how do i use this?
>

No idea - but this is weird looking if nothing else.... (I've put the abs bit in
since you specified =0 rather than <=0 )

#declare fn_Xb = function(x,y,z){0.1*pow(x,4) - x*x - y*y - z*z + 0.9}

isosurface {
  function { abs(fn_Xb(x, y, z)) - 0.1}
  contained_by { box {-10,10 } }
  accuracy 0.001
  max_gradient 250  // Eeeek!!!
  all_intersections
  pigment{Red}
}

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