"Warp" <war### [at] tagpovrayorg> wrote in message
news:<3964c652@news.povray.org>...
> Tom Melly <tom### [at] tomandluf9couk> wrote:
> : When you scale an object, all that POV does is to move all parts of the
> : object from their origin to their origin*scale.
>
>   Well, this is the impression you get, but strictly speaking it's not
true.
>   Povray doesn't move anything (it doesn't _add_ anything to the location
of
> the object).
>   Objects do NOT have origin. Povray does NOT know where the origin of an
> object is.
>   Ok, ok, let me take that back. Povray does know where the origin of an
> object is: It's at the global origin (ie. coordinates <0,0,0>). What I
meant
> was that in povray's inner world there's no such a thing as "object
origin".
>   Objects are basically mathematical functions with a matrix
transformation
> applied to it. Mathematical functions do not have "origins" except the one
> at <0,0,0>.

I realise this; however, it was explanations like this that confused the
hell out of me when I first started using POV ;) Actually, if you re-read
what I was said, you will see that we agree - just some of my terminology
differs (yours is more correct). For example, I in no way refer to objects
having an "origin" in the sense of "center". By "origin", I mean "the place
occupied by any point of an object before it is transformed", rather than
one absolute. In my examples I tried to make it plain that only that point
of an object whose origin (in my sense) resided at <0,0,0> before scaling
would remain in the same place (<0,0,0>). Even the text you posted from my
original post makes this clear ("all parts").

As for the rest, as I've said I can't find anything that really contradicts
in any fundamental way anything I wrote. More accurate, yes - but I'm not
sure how helpful matrixes are in newusers. "Move" may not be an accurate
word when talking about scaling, but it can be a helpful model when first
understanding transformations.

The trouble with learning to ray-trace is that you start with your standard
tiled floor reflecting sphere schtick, you get cocky, try modelling a
teapot, and suddenly your handle is in Havana. All you did was translate it
1 unit right (the problem is that that was before you scaled it by 500).

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