[MEI-L] Coordinate system confusion [and terminology]

Roland, Perry D. (pdr4h) pdr4h at eservices.virginia.edu
Sat Jul 8 21:12:54 CEST 2017 

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
> > > >>>>>
> > > >>>>>
> > > >>>
> > > >>
> > > >>
> > > >>
> > > >>
> > >
> > >
> > >
> > _______________________________________________
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> > 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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