On Wed, 10 Sep 2003 15:46:49 +0100, Tom Melly <tom### [at] tomandlucouk> wrote:

> "Phil Cook" <phi### [at] deckingdealscouk> wrote in message
> news:opru931zpaeybzwd@news.povray.org...
>>
>> Well looks like I can answer my own question, after a bit of
>> experimentation I think the following explains the scaling situation,
>
> <snip>
>
>> which makes sense just multiple the vectors by the scale, it's a shame 
>> that
>> the help file uses a 0 sphere as it's example, as this won't show any
>> translation (0*any number =0).
>>
>> This is probably well known and understood by POV-Ray writers more
>> competent than myself, but it confused the heck out of me at first.
>>
>
> I think everyone runs into this one at some moment - it's very tied in to 
> the
> (wrong) assumption that every pov-primitive has a defined center (which 
> could
> therefore stay in one place even when the object is scaled).
>
> Without a defined center, how could any object stay in one place when you
> changed its size?
>
> The bottom line is that it's a good idea to locate a known point of your 
> object
> at <0,0,0> prior to scaling.
>
> Extending this to all the transforms, except in special cases*, I tend to 
> follow
> what I call the 'open the door' rule - grasp the handle (scale), turn 
> (rotate),
> open (translate).
>
> * for example, for the markers on a clock-face, I would tend to translate 
> first,
> then rotate.
>
>
>

It's just a shame that it's not mentioned in the help file under scale, as 
I said thinking about it it makes sense, as a beginner though it came as a 
surprise.

Yeah, I've had fun with translate, rotate and rotate, translate when 
creating an octagonal pool, but at least I was warned with rotate (though I 
do still forget at times)

--
Phil

-- 
Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/

Post a reply to this message