Chris Huff <chr### [at] maccom> schrieb in im Newsbeitrag:
chrishuff-7E9319.13261612112000@news.povray.org...
> In article <3a0ed1ad@news.povray.org>, "Jan Walzer"
<jan### [at] lzernet>
> wrote:
>
> > Looking at the picture I think the effect comes from some
> > clipping-effects of the different rgb-values or some
> > non-continueities (you know what I mean) of the
Gamma-function
> > with negative values ...
>
> I think the gamma correction uses a continuous, non periodic
function,
> probably just a simple polynomial. The results you see are
probably from
> the color values being clipped and otherwise messed up by the
function.
>
>
> > I think, the question is: When is it applied? Before or after
AA??
>
> Gamma correction would have to be applied to the final result
of
> computing a pixel, correcting each sample wouldn't give the
right
> result. Antialiasing has little effect on the image, it mostly
makes a
> small difference in edges, so the change would be minor.

So this is what I originaly ment ... If you use the
gamma-correction(with negativ values) on an antialiased image ,
you don't have any longer the effect of antialiasing. The GC
could produce again (unexpected) stairsteps.

But: AFAIK Gamma is only defined for values > 0 ...

So does it make sense to ask if the current model is correct ???
Of course, we often have other functions in POV, working with
unrealistic values (negative pigments or lights ...[New question:
what is with negative IOR ???]), but they are or could be quite
predictable, but what do you expect from a negative gamma value
??? How would define the result ???

BTW: has someone here have the code for the gamma function ???

--

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',','   student of      >|<  mailto:jan### [at] lzernet ',','
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