Re: True Hand-engraved Dashed Slurs

[Carl Sorensen]

On 6/27/17 9:00 PM, "lilypond-devel on behalf of Carl Sorensen"
<address@hidden on behalf of
address@hidden> wrote:

>On 6/27/17 6:00 PM, "lilypond-devel on behalf of tisimst"
><address@hidden on behalf of
>address@hidden> wrote:
>
>>On Tue, Jun 27, 2017 at 3:20 PM, Kieren MacMillan [via Lilypond] <
>>address@hidden> wrote:
>>
>>> Hi all,
>>>
>>> >> Take my vote for having it as the default.
>>> > Excellent! At least that makes two of us ;-) (and Kieren, I believe).
>>>
>>> Yes.
>>>
>>
>>Cool!
>>
>>One thing I just noticed, upon closer inspection of using plain old Slur
>>overrides is that the dashes near the tips of the slurs or shorter than
>>those near the middle. This occurs because the stencil pieces are
>>parameterized with the time variable "t" internally. In other words,
>>because most slurs are longer horizontally than they are tall, the
>>progression of the time variable moves more slowly near the tips,
>>resulting
>>in shorter segments there and more quickly in the middle, resulting in
>>longer segments there. I completely understand why it is parameterized
>>this
>>way, but I'm not sure I like the output so much. Even the current default
>>dashed slurs suffer from this.
>>
>>I'm now wondering (since it looks a little odd to me to have visibly
>>shorter segments on the ends than in the middle), if there's an
>>economical
>>way to create the stencil so each segment has a more consistent length?
>>If
>>you compare the PS dashed curves and the dashed slurs with my latest
>>settings, you will see that the PS curve is much better at making the
>>segments more equal in length.

The PS curve does make the segments more equal in length.

>>
>>Thoughts? You may be tempted to think that I'm being too nit-picky and
>>maybe I am, but I think the PS dashed curve looks better due to its
>>consistency. I've attached a PDF that shows all three kinds of dashed
>>slurs, the current default, the better one using Slur Overrides, and the
>>ideal one with PS code.

I can see that the uniform dashing is better.  I am not in favor of moving
to the PS code for LilyPond, however, because we have more backends than
just PS (in particular, we have SVG).

I would be fine with having a lilypond graphic that this a dashed Bezier
curve, that could be implemented using something like your PS code in
output-ps.scm and some other code in output-svg.scm that would render it
appropriately.


>
>The slur made with your slur overrides is clearly defective. I'm not sure
>why. I will investigate.
>
>If you go to high magnification you will see that some dash ends are
>concave and some are convex.  That should never happen.

I could not replicate the problem your pdf had with broken segments.  I
don't know if it was just a case of my viewer, or not.

But the issue of non-uniform t along the length of the bezier curve is a
legitimate issue.  I am looking into it to see if there are any readily
available solutions.

This is an example of something that one would hope to benefit from if
LilyPond were to go to Cairo.

Thanks,

Carl