How to Require curve to pass through or by a point?

curves

#1

I have a curve whose original instructions are to “Curve blade seam, giving 1” of round at 16” Is there a way to do this? I’ll also need to have it do this for the sidebody panel seam.

This might be similar to Issue #395, #490 or #531. I haven’t read them yet. They’re popping up as I write this.


#2

Did you try Spline Path tool?


#3

You could create a perpendicular point at 16 using ‘Point Along Perpendicular’, with length 1". Then create the curve through the new point.


#4

You could create a perpendicular point at 16 using ‘Point Along Perpendicular’, with length 1". Then create the curve through the new point.

That’s what I did as a temporary fix for now. But, if I have a customer with different measurements the position of the curve will change. I’m trying to aim for a draft that has the least amount of manual adjustments.


#5

I’m sorry, I’m afraid I don’t see that tool. Is in the Curve tools?


#6

What I do is create an increment for a centimeter (in your case, inch) for height and one for width. #CM_HEIGHT or #IN_HEIGHT = (customer back waist length divided by the back waist length used in the original pattern) #CM_WIDTH or #IN_WIDTH = (customer chest circumference divided by the chest circumference used in the original pattern)

From 16 square out 1*#CM_WIDTH (this particular adjustment affects the fit around the torso, so use #CM_WIDTH) These formulas scale the number values up or down relative to the customer’s major measurement for height and width. This can prevent having to introduce a conditional statement like (bust_circ > 50? 1.5 : 0.75)

Sometimes I calculate the percentage in the point’s formula instead of in Increments if the formula is used only once. So the formula might look like 1.08*bust_circ. For a 38" chest, this adds about 3" to the chest girth (3.04").


#7

If you want to create curves that scale properly, create control handles. A control handle’s angle is usually the angle of the adjacent line, but sometimes one control handle will ‘point’ to the other control handle, other times the control handle is perpendicular to the adjacent line, and for tough cases a formula works best. A control handle’s length is often 1/3 the length of the curve’s base line, but many times 1/6, 1/4, or 1/2 looks better.


#8

I was also looking for a way to make a new curve pass through an already-exsting point. I ended up “manually” deriving deriving a formula for the handle lengths (the handle angles are based on the angle of the lines that connect to the cure).

It would be nice if there was a way to define a curve by a set of higher order constraints – i.e. “beginning of curve tangental to line X” AND “end of curve tangental to line Y” AND “through point P” – as an alternative to having to deal with the “lower level” curve handle angle/length values.


#9

Yes. This would make curves so much easier to create.


#10

I have created a way to have smooth ‘three point’ curves that meet each of the three points at ninety degrees. They can be either symmetrical or nonsymmetrical. Here is what they look like and how to set up the control points. I’ve also attached a .val file for you to test it out. All that is necessary is to create a ‘Curved Path’, only define three points, press ‘Enter’, then right click and set the options.

BezTest01.val (1.6 KB)

BezTest01.vit (574 Bytes)


#11

I would suggest creating a custom measurement called @bezapp (i.e. Bezier Approximation) with a value of ‘0.551915024494’ and using that in the formulas.


#12

I like to take length of lines divided by 2 or 3 in the formula for the bezier handle lengths. I also try to use the angle of lines to determine the angles. That way, I get a nice resize when I change the measurements.


#13

Just a hint, I don’t know if you know, but you could add measurements that are unique to a pattern piece directly in Valentina instead of creating or adding them to a measurement file.

Click on Variables Table and create the unique measurement in Variables:

This will be available in formulas in the Increments section and has a # in front:

Here is your file back without a .vit file necessary :slight_smile: BezTest01.val (1.6 KB)


"Maid's work Apron" (One method)
#15

(FWIW, I got that value from this page.)


#16

Oooh, ouch! That’s waaaay above my head :slight_smile: I’ll have to study it more to figure it out.

But I do like your tutorial at the top and I’m sure others will benefit from it greatly as well. I like to download the samples provided on the forum so that I can learn how others do things, as I’m still learning pattern-making.


#17

To be honest, I just skipped him detailing how he got the value and just used it. :grin:


#18

@KeithFromCanada, thank you for posting the page about approximating a circle with Bézier curves. I studied these concepts, but so long ago that I did not remember anything specific. Looking this up was on my overly long to do list