The problem is actually not a POVray one. I should have started a thread in off
topic instead.

So I can't make use of the isosurface object or the trace function.

What I ended up doing was placing random points in the blob's bounding box and
then testing whether they were inside the blob or not. A parametric equation
would result in no misses, and might have other desirable properties too such as
creating more points where the blob is densest or where the curvature is
greatest.



Mike


Alain <kua### [at] videotronca> wrote:

> > Thanks. How does that help me determine point coordinates?
> >
> >
> > Mike
> >
> > Alain <kua### [at] videotronca> wrote:

> >>> Are there parametric equivalents to the implicit metaball functions found here:
> >>>
> >>>
http://www.geogebra.org/en/upload/files/english/Michael_Horvath/Metaballs/geogebra_metaballs.htm
> >>>
> >>> I would like to plot random points withing the curves/surfaces.
> >>>
> >>>
> >>> Thanks!
> >>>
> >>>
> >>>
> >>>
> >>
> >> Take a look at the blob primitive. The sole difference is that the
> >> strength of the fields decrease in a linear fashion.
> >
> >
> >
> >
> Once the object is defined, you can use the trace function to shoot rays
> at it from random locations. Be sure to use the trace with the normal
> option. If the returned normal vector, that trace totaly missed your
> object. For any non-null normal vector, you have a valid point on the
> surface.
>
> You also use an isosurface object. It allow you to use any function you
> want. For the metaball using values diminishing relative to the
> distance, you'll need to use the reciprocal (1/function) to get useable
> result. An isosurface assume that values smaller that the thressold are
> inside the object.
>
>
> Alain

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