What's so bad about overlapping contours?

Alexis Luengas
Alexis Luengas Posts: 36
in Type Design Software
If merging the overlapping components of a glyph doesn't reduce the number of points, why bother? (Take as a good example '#', where merging doubles the number of points.)

So far, I've been reading that inner glyph intersections should be avoided, but I can only suspect it's a rendering issue.

Comments

  • Filip Blazek
    Filip Blazek Posts: 14
    At least it is important for vinyl sign cutter. You would get sixteen elements instead of one when cutting #.
  • John Hudson
    John Hudson Posts: 3,186
    Some rasterisers will display the overlapping area as a white knockout. Some outline functions will draw the overlapping elements separately. Also, what Filip said.

    [Hullo, Filip. Good to see you on TypeDrawers.]
  • Thomas Phinney
    Thomas Phinney Posts: 2,883
    edited December 2013
    Also, consider what happens if somebody applies a shadow or stroke to the glyph.
  • Russell McGorman
    Russell McGorman Posts: 262
    As Filip says, this a problem for vinyl plotters... But also for CAD/CAM operated routers and water-jet & laser cutters. Machines will make little 'hiccoughs' when they cross double nodes - which happens every now and then, even in the best of fonts. A double outline or an overlapping contour will ruin a piece and since the operator isn't likely to know the overlaps exist, can even be dangerous in some circumstances.
  • Jan Willem Wennekes
    Jan Willem Wennekes Posts: 148
    edited December 2013
    Interesting question, I'd love to hear more - I thought it was bad form/manners as well to leave them overlapped. It does create rendering issues while typing which gives the impression the typeface doesn't work properly - although in itself that shouldn't be a problem.
  • Deleted Account
    Deleted Account Posts: 739
    edited December 2013
    As the font designer defined them, overlaps should not have been a problem in fonts for the past 25 years. We say (or did before cpal et al) , in effect, "...this line defines a boundary between colors, but this line defines no colors on either side and this line has no treatment for any appearance of the lines It forms whatsoever."...leaving rasterizers the entire job of simply listening to the user.

    I have always stood for the standards on this, encouraging app developers to do so as well. And for app developers, that means listening to the definition in the standard, and then the user, and then doing the non brain damaged thing. cAd! Fuck me, they rarely kern. Sign cutters with drop shadows and contour treatments should be creating their masters in intelligent apps, like Adobe's, and if they have problems they should tell adobe, who should follow their own standards.

    And font tool wise, while others prefer to stand around and tell horror stories, a tool that allows contours, overlapping contours, composites, overlapping composites, contours and composites, as well as overlapping composites and contours, to exist in a source glyph during the design and generalization processes of founding, allowing filters to decide between rasterizer intel and file size requirements* e.g., in the productization stage... You got one?

    *if you took a hyphen, duplicated it, spun that duplicate 90 degrees and called it a plus, it should work with but 8 points. Removing overlap, makes 12 points. Doing the same to breve, doubles the size when overlap is removed for the off curve points. Glyphs with multiple curving overlaps drive up the point count dramatically. Scripts with glyphs with lots of these overlaps, triple, or worse, the file sizes of fonts carrying those scripts, perhaps to phones, where sign cutting is rare, so far.

    So what do with products, is do everything. What to do about sources, depends, on how good you want to be to yourself and all of your clients, even the ones you don't have yet, IMHO. I.E., manners have nothing to do with it;)











  • Alex Kaczun
    Alex Kaczun Posts: 163
    Ditto, David. Well said!
  • erik spiekermann
    erik spiekermann Posts: 10
    edited October 2014
    For plotting etc, always supply a PDF with fonts outlined.
  • Thomas Phinney
    Thomas Phinney Posts: 2,883
    I'm the first person to say that having overlaps in your upstream source materials is often handy! I would not want to work without that capability.

    I recently accidentally left overlaps in a pre-release version of a font, sent to my Kickstarter backers. One of them spotted it and complained, because of what the Adobe PostScript outlines rasterizer was doing to it in InDesign. http://www.thomasphinney.com/2014/01/overlapping-paths-in-type-design/
  • Wei Huang
    Wei Huang Posts: 98
    edited March 2015
    Resurrecting old thread: I'm on OS X 10.9.5 and the white gaps still show up sometimes. This is from the catalog page at WebType
    But on the specimen page, the problem is not there as that page has`-webkit-font-smoothing: antialiased` and it seems to hide the overlaps (for Safari and Chrome but not Firefox which needs Firefox specific declaration [?] ).


  • Malcolm Wooden
    Malcolm Wooden Posts: 58
    Interesting effect! This may be due to WebType using CFF outlines perhaps? I remember this kind of problem with ATM in olden days.
  • Paul van der Laan
    Paul van der Laan Posts: 242
    Hey, thanks for spotting the strange behaviour of our Pinup font! ;)

    I can assure you that this is not intended. By default we always flatten all contours before we generate final font files. But in this case it slipped through...

    We have notified the good folks at Webtype about the problem, and it should be solved soon.

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