zero-length Bézier control point on a (PostScript) curve: how bad is it?
Options

Thomas Phinney
Posts: 3,013
Sometimes, almost always from dubious sources, I see a PS curve defined in a way that one of the Bézier Control Points is placed fairly normally, or maybe even a bit exaggerated… and the other one is hidden—it turns out to be a zero-length BCP.
In some (most?) cases, this is clearly a Bad Thing. The curve is such that it should be more balanced, and it isn’t.
But in _some_ cases, it isn’t such a clearly bad thing from an appearance point of view. Something that starts out closer to a straight line and gradually curves more seems ~ reasonable. Rather like a spiro curve. Although, in such cases, usually a short but not zero-length BCP would also work pretty well.
I hae to admit, in terms of BCP criss-cross concerns, I don’t even know how to evaluate a zero-length BCP! Is it impossible for it to go wrong? Is it always wrong? Heck if I know.
Are there other technical or rendering-efficiency reasons to avoid a zero-length BCP on a curve?
(Of course, if you have _two_ zero-length BCPs defining a curve, you get a straight line; no reason to have a curve at all, unless it is for compatibility in a variable font.)
In some (most?) cases, this is clearly a Bad Thing. The curve is such that it should be more balanced, and it isn’t.
But in _some_ cases, it isn’t such a clearly bad thing from an appearance point of view. Something that starts out closer to a straight line and gradually curves more seems ~ reasonable. Rather like a spiro curve. Although, in such cases, usually a short but not zero-length BCP would also work pretty well.
I hae to admit, in terms of BCP criss-cross concerns, I don’t even know how to evaluate a zero-length BCP! Is it impossible for it to go wrong? Is it always wrong? Heck if I know.
Are there other technical or rendering-efficiency reasons to avoid a zero-length BCP on a curve?
(Of course, if you have _two_ zero-length BCPs defining a curve, you get a straight line; no reason to have a curve at all, unless it is for compatibility in a variable font.)
0
Comments
-
Some earlier discussion here.2
-
Are there other technical or rendering-efficiency reasons to avoid a zero-length BCP on a curve?Conversion to quadratic curves will produce an off curve point on top of an on curve point, which is a no-no in TrueType.
2 -
Thanks! That is super helpful!
I remembered it being A Bad Thing, and have always avoided it. I was writing about it in some guidance for newbies, only… I couldn’t remember any specific reason it was bad.0
Categories
- All Categories
- 46 Introductions
- 3.8K Typeface Design
- 476 Type Design Critiques
- 555 Type Design Software
- 1.1K Type Design Technique & Theory
- 640 Type Business
- 831 Font Technology
- 29 Punchcutting
- 507 Typography
- 120 Type Education
- 313 Type History
- 74 Type Resources
- 109 Lettering and Calligraphy
- 30 Lettering Critiques
- 79 Lettering Technique & Theory
- 533 Announcements
- 86 Events
- 110 Job Postings
- 167 Type Releases
- 169 Miscellaneous News
- 274 About TypeDrawers
- 53 TypeDrawers Announcements
- 119 Suggestions and Bug Reports