3 ms·

Yeah, editing TrueType fonts w/ B-splines which have a shared off-curve control point between two on-curve control points is nightmarish as a small change will

• dahart 2mo ago
  I haven’t done any font editing but is this true in general? Sounds like some kind of application-defined constraint. You’re talking about quadratic splines with the shared approximating point between interpolating points, and probably quadratic Bézier, not B-splines, I would guess. Quadratic Bézier would do this if the application decides to constrain all tangents to be smooth, which is a choice, not a property of the spline. Quadratic B-splines do not in general have this property; you can move any of the control points and have local control of the curve that doesn’t extend beyond the two neighboring control points. The difference is that B-splines don’t have interpolating control points in general - the curve only approximates all the control points, and you have to use phantom points or duplicated points to ensure the curve touches them.
  • WillAdams 2mo ago
    Mostly font editors use Bézier curves with four control points, so the effect of moving an off-curve point is limited to that portion of the curve from the associated on-curve node up towards the opposing on-curve node as affected by the other on-curve node. It is my understanding that only a couple of very expensive font editors use B-splines where there are three control points which ripple as I noted, however it seems that FontForge supports order2 (quadratic, TrueType) or order3 (cubic, PostScript).