Le Forgeron <jgr### [at] freefr> wrote:
> you cannot use macro (#if is macro) inside function the way you want
> to do it (different namespace: x in function space is not the same
> as the x in macro/SDL space). See 2.2.1.6.2 in
>
> http://www.povray.org/documentation/view/3.6.1/231/
>
> If you want to limit to x>0, use the contained_by { box {
> <0,-1,-1>,<1,1,1> } in the isosurface object.
>
>
> --
> The superior man understands what is right;
> the inferior man understands what will sell.
> -- Confucius



Forgeron,
Thanks for your advice. Now i got the difference of function space and SDL
space. But i still have problem in implementing function in SDL for my
isosurface.

In my scene, the isosurface is defined by implicit polynomials in terms of
b-spline basis. And the function evaluation needs the branches that depend
on coordinates of point in 3D scene space, e.g. the parameters passed to
the function. I've read many examples for definition of isosurface
functions in SDL, found that they all only the combination of basic
operations(e.g. +,-,*,/,power etc) but without the logic operations(Aand,
Or..).

So can i implement logic operations in function that will take affect in
rendering time but not parsing time? If can do it in function space, how
should i do?

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