Force length of a spline to be equal to x?

[hrab]

I think, based on viewing other topics here, that this is an unimplemented feature:

It is foundational in pattern design to have two edges which will be seamed together be of equal length. Currently, I don’t think there’s a way to create this relationship between, for example, two splines. It would be important for such a feature to accommodate updates to the measurement tables in a reasonable way.

I’m not a programmer, though I have some experience in programming. My thought is this: would it be possible to create a constraint on a new spline (maybe a new curve tool type?) which would force its length to be equal to another curve/line in the current project? I’d suggest that the software accomplish this by allowing the user to specify the start and end handle angles (tangents), and let the algorithm vary the “tension” of one or both handles (by choice) until the curve length requirement is met.

I realize that there are geometries for which this would fail outright, but experienced and careful pattern designers would get it to work, and get a lot of use from such a feature.

[Grace]

Yes, we’ve been trying to figure a practical, mathematical and geometrical way that one could program this. You may check these threads:

Curve tool with a fixed length

Hello, It would be nice to have a “Simple curve” tool with one fixed point and a fixed length to create a seam with two pieces of the same length. Perhaps the tool need a line or axis for the calculation of the sencond point.

New feature Curve tool Overlay - "French" curve

I have created this topic for people to gather thoughts and input on what should be included in a new software tool like the one mentioned in recent discussion on other threads. I will post links to those other discussions here. The “french curve” tool or specific tools used in specific patternmaking systems could be provided as an overlay on the screen so that a user could draw a new pattern against the reference. I see this as an automated way to “lay the tool against the screen”. I invite…

I’m not a programmer at all, so perhaps we can put our heads together and one of the programmers will get some inspiration and come up with a tool?

[hrab]

Just out of curiosity, how are users handling this problem currently?

[Grace]

I fiddle with the handles in options until I get it the length I want it to be. With a bit of practice, you get it right quite quickly.

[bernt]

I create a line (point at distance) with the length equal to the difference of the length from the two curves. If this line is short enough, then the pattern is ok.