"Wlodzimierz ABX Skiba" wrote:
> Four tangents describe four directions.

Yes.

> What about deformation which operate on space between this
> directions and leave space along this directions ?

What do you mean by that? Show me such a deformation!

> For example imagine that your tangents are on axis x,z,-x,-z
> and normal point somewhere up. Than imagine such deformation:
> deform(P)=<P.x*(2^P.z),P.y,P.z*(2^P.x)>

That is not a valid deformation. It generates negative fractional powers.
( For example, when P.z is -0.5 (2^P.z) will generate an error. )

You was also a bit unclear with the details. For input I need a point vector
and a normal vector. If you give me that, and a valid deformation, I can
show you that it doesn't matter which 4 tangents are used.

> there is need - accuracy of floating point operations !!!

That would not likely be a problem, but it would be very simple for me to
make the lengths user-defined, if that makes you happy...

> I don't want say that this method is wrong at all, I want
> say that this method could be wrong for some situations

Maybe, but I can't know before you show me one.

> And I want to say that you can use personalized deform_of_normal
> to achive exact (!) method value of deformed normal instead of
> aproximated ( news:3a34cd8f@news.povray.org )

I don't know what you're talking about, and I didn't find the answer in the
messege you linked to. What do you mean by "personalized deform_of_normal"?

Rune
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