Re: Lines and Ties and Slurs oh my!

[Janek Warchoł]

hello,


2014-02-14 22:01 GMT+01:00  <address@hidden>:
>          Notice that Ties in bar 1 are different than Ties in bar 2 or bar
> 4 or bar 7. Termination
>  of the Tie is not consistent.

some of this inconsistency is due to issues that Phil pointed out, but
I agree that this output is not optimal.

>           So first we need to ask the question: How should Ties be drawn?
> Specifically
> where should the Tie terminate relative to the notehead?

As Phil wrote this depends on many factors, including whether there
are notes in other voices or chords. There is no single answer that
would apply to all ties.

After a lot of thinking (i mean, 100-150 hours of thinking? something
like that) i have a pretty good idea how correct ties should look
like.  Unfortunately, it is not easy to express it in a way that a
computer understands (but it is possible).

>           Ties in bar 1 and bar 3 terminates at the "inside upper corner"
> of the notehead. Ties in
> bar 4 and 7, terminate "above / below and in the middle" of the notehead.
> Which is
> correct?

m. 2 and 3 is correct, 4 is wrong, 1 and 7 are slightly wrong.

> Slurs should
> terminate in the middle of the note to distinguish between Ties.

Generally, yes.

>          Is there a general fix for this across the broad section of
> examples?

Not quite. we have to rewrite lily's tie formatting code to fix this completely.

>         One solution is to use \shape to fix individual Ties. If I define
> a couple of
> macros
>
>      * to fix ties in bar 4, 13  (TieDown_stemsUpUp)
> TDUUa = \shape #'((0.6 . 0.4)(0 . 0.6)(0 . 0.6)(-0.6 . 0.4)) Tie
>
>     * to fix ties in bar 7 (TieUp_stemsDownDown)
> TUDDa =  \shape #'((0.6 . -0.2)(0 . -0.3)(0 . -0.3)(-0.6 . -0.2)) Tie
>
>
>        The results of the above can be seen here
>
> http://www.gooeytar.com/projects/BWV-988/test/test.pdf
>
>        Are they correct now?

They are definitely better.

> Is there another better way to deal with this?

Rewrite tie fomatting code :(

>        It is certainly possible to go through the 100+ or so "bad" Ties
> manually and I expect
> that there are simple fixes like the above that will correct common
> categories
> of bad Ties; for example all Ties between notes that are on upper ledger
> lines with
> stems down are drawn incorrectly with termination in the middle of the
> notehead (like a slur).
> Some preliminary testing has led me to conclude that the same fix (like
> above) may typically
> fix the same situation regardless of the length of the Tie or the value of
> the notes....

Yes, I have done this with the Fried edition
(http://lilypondblog.org/2014/01/engraving-statistics-slurs-and-ties/)
- 500 fixed ties...
And i have collected more than 500 tie examples over the last two
years, analyzing of which gave me some conclusions but i didn't have
enough time to fix the darn thing.  If you'd like, i can share my
research with you.

Unfortunately, i have very little time for lilypond now, so i cannot
do much more.  If you'd like to start seriously working on this issue,
i'd be happy to provide some guidance, feedback and testing.  I
estimate that anyone who wants to really fix this would have to spend
20-30 hours on researching tie shapes (i.e. reading my research),
10-20 hours to get an idea how lilypond thinks about ties now, 40-80
hours on writing new algorithms and then 20-60 hours on testing and
fixing corner cases.  With that amount of effort, it should be
possible to create an almost-perfect tie formatting algorithms (i
mean, an algorithm that formats 99.9% ties correctly, as opposed to
50% success rate now).

I'm sorry if this sounds discouraging, but that's how it is.

best,
Janek