Warp <war### [at] tagpovrayorg> wrote:
> > Now here we have a request to make the macro "more elegant and 'all-inclusive'"
> > - does that sound like the OP desires to impose *additional* requirements on
> > the caller, like telling the macro what type of spline it is to be dealing
> > with?
>
>   He talks about rewriting the code but makes no mention about preserving
> the interface to the macro.

Yes, I was sidetracked by your ranting, and perfectly forgot what my initial
motivation was to assume that passing the whole spline type & control points
was not an option. Looking back at the original posts reminded me.

He talks about rewriting the macro to make it "more-elegant and
'all-inclusive'". I'd never consider a macro to receive the whole spline type
and parameters as distinct parameters (whether discrete or as an array) to fit
that bill - or even come anywhere close.

You can't make the macro "more elegant and 'all-inclusive'" that way - to the
contrary, you'd just clutter it up and make it outright ugly. And a PITA to
use.

Again a fundamental impossibility. Which I took for granted in this case, yes.


> > ------ Me:
> > It's fundamentally impossible to do that.
> > ------
>
> > This is me referring to the task of making the macro work for the value of zero
>
>   It sounds more like you were saying that achieving "exact alignment"
> is fundamentally impossible.

I don't really care what it *sounds* like to *you*. Obviously you simply
misunderstood my post there.

The only reference in the OP to "exact alignment" that I posted was this
(emphasis added):

"the code should be rewritten to be more elegant and 'all-inclusive,' so to
speak--SO THAT A VALUE OF ZERO IS EXACT ALIGNMENT"

Why you put so much emphasis on "exact alignment" only and perfectly ignored the
context is far beyond my grasp.


>   Your explanation is a bit shaky, IMO. You are argumenting why calculating
> a derivative is impossible because all you get is a 0/0 (because the points
> are infinitesimally close to each other).

Aaaah - now *THAT* sounds much different now. With "IMO shaky" instead of
categorical statements along the lines of "that's a lie", I have no problem
accepting your position.

My attempt was to give a short overview of the problem, with the focus on where
that near-but-not-quite-zero comes from in the first place; I never meant to
write a scientific paper about the issue.

If you find it too shaky - fine; you never were the "target audience" of my post
anyway. I'll leave it up to the OP to decide whether it was helpful or not.


>   I was not disagreeing with the point that a vector of zero length has
> no direction (which is what I wrote in my reply to the OP as well). I was
> disagreeing with your statement that getting a completely accurate result
> is essentially impossible (sans the inaccuracies of floating point).

.... which, as we have seen, wasn't really my statement, but rather what you
misunderstood it for. And you took a long time to figure that out.

> > You want to make a macro more elegant by forcing the user to re-supply *all* the
> > values he has already placed in the spline definition?
>
>   As I said many times, it would be impractical, but perfectly possible.

.... and perfectly "un-elegant", thereby missing one of the OP's main goals.

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