[MEI-L] Coordinate system confusion [and terminology]
Klaus Rettinghaus
klaus.rettinghaus at gmail.com
Sun Jul 9 17:15:07 CEST 2017
I strongly recommend to stick with virtual unit! Talking about space
could lead to the assumption that it's about the space _between_ two
lines. But as a line by itself has a defined width, a space would
merely be "the space between two adjacent staff lines plus the width of
one staff line, which is confusing.
The Guidelines are already very precise about that:
"A single vu is half the distance between the vertical center point of
a staff line and that of an adjacent staff line."
And after all, a "vu" isn't just about musical context, i.e. "things"
on or around a staff, but a real (relative) measurement unit for the
whole layout.
--
Klaus
Am Sa, 8. Jul, 2017 um 9:55 schrieb Roland, Perry D. (pdr4h)
<pdr4h at eservices.virginia.edu>:
>
> If there's support from the community, I'm fine with changing "vu" to
> "hs". If we're going to break it, let's break it now.
> In the schema and Guidelines, it's a simple search-and-replace.
> Changes to existing markup can be built into the version 3 to version
> 4 XSLT. But I can't speak to changes to Verovio and other MEI-based
> software, so if there are objections from developers, speak now
> please.
>
> --
> p.
>
>> -----Original Message-----
>> From: mei-l [mailto:mei-l-bounces at lists.uni-paderborn.de] On Behalf
>> Of Byrd, Donald A.
>> Sent: Saturday, July 08, 2017 3:34 PM
>> To: Music Encoding Initiative <mei-l at lists.uni-paderborn.de>
>> Subject: Re: [MEI-L] Coordinate system confusion [and terminology]
>>
>> I understand the issue. But I think just saying
>> "half-STEPS/diatonic steps" instead of "half-
>> spaces/diatonic steps" and half-spaces (hs for short) instead of
>> virtual units (vu for short)
>> would do the job. No need to change the unit, just the term.
>>
>> Thanks for listening! I'll shut up now.
>>
>> --DAB
>>
>>
>> On Jul 8, 2017, at 3:12 PM, "Roland, Perry D. (pdr4h)"
>> <pdr4h at eservices.virginia.edu>
>> wrote:
>>
>> >
>> > Don,
>> >
>> > Like I said before, changing MEI's unit of measurement from
>> half-spaces/diatonic steps
>> to spaces would break all existing markup and software. Changing
>> the markup is
>> reasonably easy, but modifying software is another problem all
>> together. So, unless there's
>> a HUGE outcry from the community, I'd prefer to leave things as
>> they are.
>> >
>> > --
>> > p.
>> >
>> >
>> >> -----Original Message-----
>> >> From: mei-l [mailto:mei-l-bounces at lists.uni-paderborn.de] On
>> Behalf Of Byrd, Donald
>> A.
>> >> Sent: Saturday, July 08, 2017 2:48 PM
>> >> To: Music Encoding Initiative <mei-l at lists.uni-paderborn.de>
>> >> Subject: Re: [MEI-L] Coordinate system confusion [and
>> terminology]
>> >>
>> >> Before my original suggestion is completely forgotten, I'd like
>> to
>> >> back up a little. Perry, you said
>> >>>
>> >>> I have trouble, as I think most folks would, with values like
>> "2-1/2
>> >>> half-spaces". I can
>> >> live with "2-1/2 steps", but still prefer "2-1/2 vu". We
>> can/should
>> >> define a "vu" in relation to diatonic steps though.
>> >>
>> >> Gould and Read rarely if ever saying anything like "2-1/2
>> >> half-spaces"; the example I gave, and what they actually say, is
>> "2-1/2 SPACES". And
>> the fact the "spaces"
>> >> terminology is used consistently by both in works intended for
>> >> practical use seems like pretty good evidence that that
>> terminology doesn't bother
>> people much.
>> >>
>> >> Let's see, here's a random note in a random piece of music; I
>> wonder how long its stem
>> is?
>> >> Ah, it extends all the way across three spaces and halfway across
>> >> another! :-). It's a standard one-octave stem, with a length of
>> 3 and 1/2 spaces.
>> >>
>> >> --Don
>> >>
>> >>
>> >> On Jul 7, 2017, at 4:41 PM, "Roland, Perry D. (pdr4h)"
>> >> <pdr4h at eservices.virginia.edu>
>> >> wrote:
>> >>
>> >>> Yes, 1 vu = 1 diatonic step. However, the phrase “diatonic
>> step”
>> >>> doesn’t actually appear in the definition –
>> >>>
>> >>> “A single vu is half the distance between the vertical center
>> point
>> >>> of a staff line and that
>> >> of an adjacent staff line.”
>> >>>
>> >>> Even this definition occurs within the description of
>> @vu.height.
>> >>> This is definitely a
>> >> place where the Guidelines could use some work.
>> >>>
>> >>> --
>> >>> p.
>> >>>
>> >>>
>> >>> From: mei-l [mailto:mei-l-bounces at lists.uni-paderborn.de] On
>> Behalf
>> >>> Of Craig Sapp
>> >>> Sent: Friday, July 07, 2017 2:58 PM
>> >>> To: Music Encoding Initiative <mei-l at lists.uni-paderborn.de>
>> >>> Subject: Re: [MEI-L] Coordinate system confusion [and
>> terminology]
>> >>>
>> >>>> We can/should define a "vu" in relation to diatonic steps
>> though.
>> >>>
>> >>> Is that not already the case? Otherwise, I am confused... In
>> other
>> >>> words 1vu = 1 diatonic
>> >> step (such as E to F, or G-flat to A-sharp since the chromatic
>> alteration does not
>> matter).
>> >>>
>> >>>
>> >>>
>> >>> On 7 July 2017 at 20:45, Roland, Perry D. (pdr4h)
>> >>> <pdr4h at eservices.virginia.edu>
>> >> wrote:
>> >>>
>> >>> I have trouble, as I think most folks would, with values like
>> "2-1/2
>> >>> half-spaces". I can
>> >> live with "2-1/2 steps", but still prefer "2-1/2 vu". We
>> can/should
>> >> define a "vu" in relation to diatonic steps though.
>> >>>
>> >>> --
>> >>> p.
>> >>>
>> >>>
>> >>>> -----Original Message-----
>> >>>> From: mei-l [mailto:mei-l-bounces at lists.uni-paderborn.de] On
>> Behalf
>> >>>> Of Byrd,
>> >> Donald A.
>> >>>> Sent: Friday, July 07, 2017 11:23 AM
>> >>>> To: Music Encoding Initiative <mei-l at lists.uni-paderborn.de>
>> >>>> Subject: Re: [MEI-L] Coordinate system confusion [and
>> terminology]
>> >>>>
>> >>>> Sure. As I said, both Gould and Ross talk about "half spaces".
>> >>>> --DAB
>> >>>>
>> >>>> On Jul 7, 2017, at 11:03 AM, "Roland, Perry D. (pdr4h)"
>> >>>> <pdr4h at eservices.virginia.edu>
>> >>>> wrote:
>> >>>>
>> >>>>>
>> >>>>> Hi Don,
>> >>>>>
>> >>>>> You make a good argument for the term "staff-space" or
>> "space".
>> >>>>> However, MEI doesn't
>> >>>> use this distance as its unit of measurement. Instead, MEI uses
>> >>>> *half the distance* between adjacent staff lines, hence the
>> need
>> >>>> for a different term. Perhaps "interline distance" and
>> "virtual
>> >>>> unit" aren't intuitive, but they
>> >> accurately describe the situation, which "staff-space"
>> >>>> or "space" do not. Of course, we could start using the entire
>> >>>> distance between staff lines as the unit, but that would mean
>> >>>> changing all existing MEI
>> >> markup and software.
>> >>>>>
>> >>>>> --
>> >>>>> p.
>> >>>>>
>> >>>>>
>> >>>>>> -----Original Message-----
>> >>>>>> From: mei-l [mailto:mei-l-bounces at lists.uni-paderborn.de] On
>> >>>>>> Behalf Of Byrd, Donald
>> >>>> A.
>> >>>>>> Sent: Tuesday, July 04, 2017 11:26 AM
>> >>>>>> To: Music Encoding Initiative <mei-l at lists.uni-paderborn.de>
>> >>>>>> Subject: Re: [MEI-L] Coordinate system confusion [and
>> >>>>>> terminology]
>> >>>>>>
>> >>>>>> This reminds me of another source of coordinate system
>> confusion,
>> >>>>>> namely the term for the distance between staff lines. Verovio
>> >>>>>> source code calls it a "double unit", and half that distance
>> a
>> >>>>>> "virtual unit" or "VU" or just
>> >>>> "unit"; none of those terms is at all intuitive.
>> >>>>>> Johannes calls it the "interline distance", which is much
>> better,
>> >>>>>> but rather long, and "half interline distance" is way too
>> long
>> >>>>>> (and clumsy). Well, look at Chapter 1 of _Behind Bars_. Her
>> term
>> >>>>>> is "stave-space", or just "space" for short; half that
>> distance,
>> >>>>>> of course, is a "half space". Ross' _Art of Music Engraving
>> and
>> >>>>>> Processing_, the only other book I know of that says much on
>> the
>> >>>>>> subject, just uses the
>> >>>> term "space'. So, for example, both might describe a certain
>> stem
>> >>>> length as "2-1/2
>> >> spaces".
>> >>>>>>
>> >>>>>> I submit "stave-space" (or "staff-space" on my side of the
>> >>>>>> Puddle) as the full term and "space" for short are both the
>> most
>> >>>>>> standard and the
>> >> best terms.
>> >>>>>>
>> >>>>>> --Don
>> >>>>>>
>> >>>>>>
>> >>>>>> On Jul 4, 2017, at 11:16 AM, Daniel Alles
>> >>>>>> <DanielAlles at stud.uni-frankfurt.de>
>> >>>>>> wrote:
>> >>>>>>
>> >>>>>>> Thank you, Johannes, that really helped and made that
>> clear. So
>> >>>>>>> I can continue using the
>> >>>>>> Edirom-coordinates for ulx etc.
>> >>>>>>>
>> >>>>>>>
>> >>>>>>>
>> >>>>>>> Zitat von Johannes Kepper <kepper at edirom.de>:
>> >>>>>>>
>> >>>>>>>> Dear Daniel,
>> >>>>>>>>
>> >>>>>>>> that's a real confusion, and we need to make it clearer in
>> the
>> >>>>>>>> guidelines. *Pixel* coordinates are always with the origin
>> in
>> >>>>>>>> the top left corner. *Music* coordinates, however, are
>> always
>> >>>>>>>> bottom up. @ulx and so on are always in pixel units, but
>> @vo
>> >>>>>>>> (vertical
>> >>>>>>>> offset) is specified in interline distances (half the
>> distance
>> >>>>>>>> between two staff lines, or, in other words, the vertical
>> >>>>>>>> distance between a C4 and a D4, or any other two adjacent
>> >>>>>>>> notes). If you want to specify that a dynamic is written
>> above
>> >>>>>>>> its default position, it seems more natural that values go
>> up (i.e., @vo="3").
>> >>>>>>>> This means that for musical units the origin has to be
>> bottom left.
>> >>>>>>>> I know it's confusing in the guidelines, and we will
>> address
>> >>>>>>>> this at some point. If you don't mind, you're invited to
>> >>>>>>>> prepare something on Git and submit a pull request ;-)
>> >>>>>>>>
>> >>>>>>>> Hope this helps,
>> >>>>>>>> jo
>> >>>>>>>>
>> >>>>>>>>
>> >>>>>>>>> Am 04.07.2017 um 14:48 schrieb Daniel Alles
>> >>>>>>>>> <DanielAlles at stud.uni-
>> >>>> frankfurt.de>:
>> >>>>>>>>>
>> >>>>>>>>> Dear all,
>> >>>>>>>>>
>> >>>>>>>>> at the moment, I am a little bit confused about how MEI
>> >>>>>>>>> defines its coordinate
>> >>>> system:
>> >>>>>> It is possible to add the attributes @ulx, @uly, @lrx and
>> @lry to
>> >>>>>> for example a surface, as written in part 12 of the
>> Guidelines,
>> >>>>>> which places the origin of the coordinate system in the upper
>> >>>>>> left corner. All the examples in
>> >>>> that part show that behavior, ulx/uly is always 0/0.
>> >>>>>> This would correspond to the coordinate systems used in SVG
>> and
>> >>>>>> DOM and (which is what I use for my work) Edirom Editor. On
>> the
>> >>>>>> other hand it is written in part 22.3, that MEI uses a
>> coordinate
>> >>>>>> system in which "the y-axis points from bottom up". That
>> would
>> >>>>>> mean, that ulx/uly could never
>> >>>> be 0/0.
>> >>>>>>>>>
>> >>>>>>>>> So now my questions: Is it sufficient to use the
>> coordinates
>> >>>>>>>>> like in the examples, with
>> >>>>>> the origin in the upper left corner? Would that "override"
>> MEIs
>> >>>>>> original coordinate
>> >>>> system?
>> >>>>>> If not: Isn't the possibility to encode areas from top-left
>> to
>> >>>>>> bottom-right corners a semantic error in MEI, if the
>> coordinate
>> >>>>>> system is pointing from
>> >>>> bottom-left to top-right?
>> >>>>>>>>>
>> >>>>>>>>> Best,
>> >>>>>>>>> Daniel
>> >>>>>>>>>
>> >>>>>>>>>
>> >>>>>>>
>> >>>>>>
>> >>>>>>
>> >>>>>>
>> >>>>>>
>> >>>>
>> >>>>
>> >>>>
>> >>> _______________________________________________
>> >>
>> >>
>> >>
>> >>
>> >> _______________________________________________
>> >> mei-l mailing list
>> >> mei-l at lists.uni-paderborn.de
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>>
>> ---
>> Donald Byrd
>> Woodrow Wilson Indiana Teaching Fellow
>> Adjunct Associate Professor of Informatics Visiting Scientist,
>> Research Technologies
>> Indiana University Bloomington
>>
>>
>>
>>
>>
>>
>>
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