"Chaanakya" <nomail@nomail> wrote:
> Hey guys!  I just had a quick question...
>
> I was trying to generate the graph of this function (in Cartesian coordinates):
>
> -z + 1.00003 = (3x^2 + 3y^2)/(200000)
>
> However, when I render the following code, nothing shows up except for the
> plane:
>
> #version 3.6;
> #include "colors.inc"
>
> global_settings {
>   max_trace_level 256
>   ambient_light White
>   assumed_gamma 1.0
> }
>
> camera {
>   location <10,10,0>
>   look_at <0,0,0>
>   // rotate <0,0,-clock*90>
> }
>
> light_source {
>   <1000,1000,0>
>   color White
> }
>
> plane {
>   y, -10
>   pigment { hexagon Green, White, Blue }
> }
>
> isosurface {
>   function {
>     -y - ((3*pow(x,2) + 3*pow(z,2))/(200000)) + 1.00003
>   }
>   // contained_by { box { -2,2 } }
>   pigment {
>     color Red
>   }
> }
>
> I'm assuming that even though z = -x (in POV-Ray), it doesn't really matter for
> the equation since x (in the equation) is squared.  Thanks in advance!
>
> - Chaanakya

Even more strangely, when I use the equally valid function

function {
  y + 3*pow(x,2)/200000 + 3*pow(z,2)/200000 - 1.00003
}

I get a cube.  I think there's something fundamental about isosurfaces that I'm
not understanding?  That is, how should I convert the function z = -3x^2/200000
- 3y^2/200000 + 1.00003 into an isosurface?

- Chaanakya

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