Re: [artworks] Artefacts on Artistic Lines
- From: Tim Powys-Lybbe <tim@xxxxxxxxx>
- To: artworks@xxxxxxxxxxxxx
- Date: Sun, 24 Jun 2012 23:16:00 +0100
On 24 Jun at 17:11, Richard Ashbery <riscos@xxxxxxxxxxxxx> wrote:
> In article <0824e7a452.martin@xxxxxxxxxxxxxxxxxxx>, Martin Wuerthner
> <lists@xxxxxxxxxxxxxxx> wrote:
> > In message <52a4e513b3riscos@xxxxxxxxxxxxx> Richard Ashbery
> > <riscos@xxxxxxxxxxxxx> wrote:
>
> > > I realise that rendering tight curves gives rise to artefacts (see
> > > the heading "Avoiding problems with troublesome centre lines" in
> > > the manual) but one particular Profile, the Wave ribbon is
> > > particularly annoying. There is a subtle tiny line artefact that
> > > appears at the junction of the "broken" paths. You are only aware
> > > of it when an outline is applied.
>
> > > is there anyway of overcoming this problem? Details of the problem
> > > can be seen here.....
> > >
> > > http://homepages.nildram.co.uk/~riscos/problems/Artefact.zip
>
> > This tiny gap at the break point is caused by the fact that Artistic
> > Lines always have a start and an end. It is not related to the fact
> > that you have to open the shape to apply the Artistic Line because
> > you can even close the shape again after applying it, and that does
> > not make any difference.
>
> I didn't understand that at the time but your explanation helps
> explain why closing the shape doesn't have any effect.
>
> > The computations at the start and the end of the line are always
> > prone to being out by a fraction of a pixel, leading to a tiny gap
> > at least on one side of the midpoint. As you noticed, that gap is
> > nearly invisible unless you apply an outline to the Artistic Line.
>
> > There is a relatively simple way around this: Just make sure that
> > the start and the end of the line overlap slightly (but beware of
> > ArtWorks auto-closing the shape, which gives you identical start and
> > end positions, so there is no overlap). That will lead to a tiny
> > double peak at the position where the start and the end of the
> > Artistic Line meet because the two thickest parts of the line are no
> > longer exactly on top of each other, but that is hardly noticeable,
> > even with an outline applied.
>
> Yes that works - if procedure is done at very high magnification then
> the paths can be made to overlap relatively simply without shape
> auto-closure.
>
> Thanks for the tip Martin and for providing such an excellent variety
> of profiles. I can't immediately think of anymore.
I may well have got something wrong but at the top of Richard's artefact
was a point. I observed this when I selected the shape and then did
Menu > Lines/Shapes > Make shapes. I selected this point, switched to
Path editing and deleted it: the artefact vanished and the shape then
seemed to me to be perfect. Though at a magnification of 4000, the
highest I could set, there does seem to be a double point at the base of
where the artefact had been. At other points on the shape there also
appear to be these 'double-points'. My view is that the Artefact was
the result solely of this surplus point at its top and which I had
deleted.
It may well be that my use of 'Make shapes' does something else that
will lead to other problems.
--
Tim Powys-Lybbe tim@xxxxxxxxx
for a miscellany of bygones: http://powys.org/
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