Older blog entries for haruspex (starting at number 106)

15 Sep 2004 (updated 15 Sep 2004 at 04:51 UTC) »
raph, circle segments are indeed the primitive used by IKARUS, as I've mentioned here before. This is clear from the exposition in Dr Karow's book (op cit.) and the source code therein. Also, I relate them to METAFONT deliberately, as this was explicitly the ideal around which Hobby's Bezier generation was designed. Again, this is derived from the technical descriptions given in The METAFONTbook. Of course, I know METAFONT's underlying representation and rendering engine works with Beziers, but concerning the higher level user abstraction, I stand by what I have asserted. I understand where Hobby departs from pure circles. In fact METAFONT's overall approach seems to solve most of the difficulty.

circular arcs do not have this property. You need quite a few of them to closely fit an ellipse, say.
Yes, I agree with what you write here, but I am not sure it matters. The fact is, any geometrical figure - ellipse, circle, parabola - is irrelevant to the problem of fitting a natural, drawn curve. Pure geometric shapes (with the exception of straight lines) rarely occur in a letter outline, so I disregard them as modelling test cases. Instead, I ask, how well can this primitive deal with a pre-mathematical, natural curve, as might have come from the designer's hand? How awkward is the translation? (Your curve continuity arguments are relevant theoretical ammunition here I think, although my assessments are usually subjective, not objective.)

My counter-assertion would be, for a natural curve, Beziers are not necessarily better than circle segments and further that counting control points does not prove this either way. My gut tells me that Beziers are excellent for rendering purposes but horrible for curve modelling. I certainly see advantages for Cornu over both these representations, and you've given some interesting reasons.

I have studied many IKARUS markups and not found them excessively overspecified. (It would be nice to hear from an IKARUS veteran on this.) One very intriguing thing about IKARUS is that most markups I've seen were made by non-technical draughtsmen, usually type designers themselves - Zapf, Frutiger, Spiekermann. Whereas no-one can do good Bezier drawings without a lot of training - and such drudgery would waste the time of a designer of this calibre. It took me a few years to learn how to "trick" Beziers into looking natural - and it's always a compromise.

In sum, my subjective assessments generally lead me to feel that IKARUS splines - or let's say, a mechanical spline and ducks - are quite natural to the draftsman and designer; and Beziers could not be more artificial and difficult.

We are coming at this from different angles, however. You're the mathematician, and I am just a typographer who isn't happy with the compromises that plague digital type.

13 Sep 2004 (updated 14 Sep 2004 at 01:42 UTC) »
raph:
I've also been playing with the Cornu spline...as a primitive for curve design, and am now absolutely convinced that it's better than Bezier curves.
I think it's long been clear that Beziers are not a good user abstraction for curve editing - but what's wrong with circle segments between on-curve knots, as chosen by IKARUS, METAFONT, et al? I am not sure anything could be more natural. I suppose the Cornu could be seen as a French-curve style extension of circles. I think I need to write that experimental path editor I always planned, to play with these alternatives :)

My hot metal friend Nick Summers is not out of the game. He wrote me recently with very exciting news:

I should finally be printing - letterpress, of course - by the end of this month ... I hope to be assembling the fabled Benton Engraving Machine some time soon as well. And restoring my Linotype. And casting on the Monotypes...
5 Sep 2004 (updated 5 Sep 2004 at 06:08 UTC) »
nymia: I wrote a Photoshop plugin that's downloaded 100 times a day. It's free. If I had put even a very modest sticker price on it, I'd be lucky to get one download a day. I decided that a comparatively large benefit to "the all" was preferable to a small benefit to me.

(update) nymia: The benefit I receive is the traffic. There are a couple of commercial and donation-ware plugins available from the same page, which should account for a small trickle of compensation flowing back from the free-loaders? It will never pay my mortgage, but it is -something-. After all, I only wrote the software once, if I get paid 100,000 times that might not be ethical. I don't want the bad Karma of uber-thief Gates and his kind.

1 Sep 2004 (updated 1 Sep 2004 at 09:46 UTC) »
TheMuso:
If you are aware of Australian internet access, it is quite different to the rest of the world, particularly broadband. I am sitting here on a 512/128K ADSL internet connection,

I am not sure what you mean, "different", unless you mean very very expensive. My Melbourne ADSL costs A$170 per month for 512kbps and an embarrassingly small download inclusion. I presume you're luckier to be paying less than this extortionate rate.

Gah. Couldn't figure out why OS X's integrated WebDAV handling wasn't working (WebDAV servers are first class file systems on OS X). Eventually figured out the problem was my squid proxy server - which at 2.2.5-4 is too old (old Debian 2.2 install on Alphaserver).

21 Aug 2004 (updated 21 Aug 2004 at 15:08 UTC) »
movement: hey, thanks for pointing out the idiotic Olympic linking policy. Taken with their ridiculous stance on blogging it makes them look like a bunch of dumb shits.
14 Aug 2004 (updated 15 Aug 2004 at 01:32 UTC) »
raph: IKARUS and Hobby's method both combine, from a user p.o.v., on-curve points with circle segments. I have long believed that this is close to the optimal curve construction technique. Hobby gets bonus points for doing it within the ubiquitous cubic B├ęzier framework!

I'm not sure what you mean when you say IKARUS uses Hermite splines; as far as I know it uses circle segments between on-curve knots. This is confirmed by the FORTRAN code that Dr Karow included as an appendix to his book Digital Formats for Typefaces.

You're right about CMR versus ink spread/squash. Some offset printed books set in CMR were disastrously thin in their setting. Wolfram's The Mathematica Book was one example. Beautifully printed, with almost no ink spread or dot gain, but the CMR type used throughout was most unpleasantly thin! Knuth was somewhat savvy to this issue as the models he looked up to were letterpress works such as early editions of his TAOCP (which are masterpieces of technical setting). He did include some compensatory parameters in his CMR metafonts to deal with print machinery characteristics, but perhaps some high resolution fonts were generated with unwise or default values.

Many digitisations and revivals, particulary Baskerville, Century and similar, have suffered from an underestimation and/or underappreciation of letterpress effects. I believe this issue has been studied pretty thoroughly by revival-makers (revivalists?) in the last 20 years or so.

California sees the light: Terrific paper on "Exploring Open Source alternatives" from the California Performance Review. A state that bans electronic "voting" and is also open to Open Source! What a place.

[Advogato bug: re-editing articles duplicates <p> tags between paras...]

mathieu, mpr: this may dampen your enthusiasm for Numerical Recipes.
mathieu: one friendly expert on floating point is Steve Richfield. I'm sure he - or another FP guru - can give you some good references if you ask on comp.arch.arithmetic.

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