New algorithm: Italify – optically corrected obliques

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  • Thomas Phinney
    Thomas Phinney Posts: 3,120
    Just to clarify: inflection points are only a problem for outline interpolation if both the angle, and the relative proportions of the distance of the off-curve points, changes.

    In neither of the models being discussed will this usually be a problem. If the points are vertical, then the angle is constant. In Sebastian’s model — unless I greatly misunderstand! — then those formerly vertical points are now at the italic angle, but consistently so.

    The only time Sebastian’s model would become a problem in this sense would be if one were doing a variable font and it had a continuous axis for italic or slope.
  • John Hudson
    John Hudson Posts: 3,633
    Re. nodes at extrema, note that a lot of us are generating both TTF and CFF from our design sources, and failing to put nodes at curve extrema in TrueType messes up bounding box calculations. That’s one of the reasons I still maintain this as a production requirement. Which is not to say that this is a necessary feature for a tool such as that @SCarewe is developing, only that it means some people might need a second step with another tool to add the nodes at extrema.

    [I used Matt Burvill’s Letterital service recently, and have been impressed by the level of control he has over glyph architecture, curvature and stroke weights. At my request, he updated his tool to calculate and insert new nodes extrema (and remove the slanted ones).]
  • SCarewe
    SCarewe Posts: 38
    edited 10:13AM
    @Typedesigner

    You are just repeating yourself. Yes, we know that nodes on extremes are a good practice, for a multitude of reasons.

    However, as explained, these reasons are not necessarily applicable in slanted fonts. Or do you have a concrete, objective reason why they should be technically necessary in slanted fonts?
  • Simon Cozens
    Simon Cozens Posts: 828
    I agree with Sebastian. "This is bad because stuff breaks" is dogma that may change over time as "stuff" evolves. "Specific application X version Y has obvious rendering failure Z if you don't put nodes at extremes" is testable.
  • SCarewe
    SCarewe Posts: 38
    edited 10:22AM
    Sorry Thomas and John, I didn't see your comments. I was replying to "Typedesigner". Thanks for your input!

    Matt's tool indeed has a slightly different approach, but the same core idea, from what I gathered when talking to him.

    Thomas: Yes, the consistency is what I'm trying to achieve as much as possible. That's why keeping the nodes on slanted extremes makes the most sense; It keeps everything as consistent as possible from a mathematical point of view and prepares the outlines best for interpolation and related operations afterwards.

    By the way, since you mention a continuous slant axis: Slanted extremes are actually much better here. See this thread on the Glyphs forum, specifically this post.
  • Typedesigner
    Typedesigner Posts: 97
    edited 10:47AM
    @SCarewe

    You’ve made your point clear several times. Whether or not you create a script that doesn’t generate extreme points in italic fonts is up to you. However, you wrote that your script isn’t finished yet, and that you don't know if you'll make it available to FontLab 8 users. This is why the whole discussion feels very theoretical to me.

    If you do decide to release your script to FontLab 8 users, we'll be able to test it in practice. In principle, I think the idea of a script that corrects italic slant is a good one. However, the next version of FontLab may offer this feature, rendering third-party scripts unnecessary. 

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