ab3204f9f1
The replaces the NextJS site powering FreeSewing.dev with a Docusaurus setup. It's part of my efforts to simplify FreeSewing's setup so we can focus on our core value proposition.
77 lines
3.1 KiB
Text
77 lines
3.1 KiB
Text
---
|
|
title: Adapt the sleevecap length to fit the armhole
|
|
---
|
|
|
|
Fitting the sleevecap to the armhole means that we need to make sure the length
|
|
of the seams match. A similar challenge is to fit the collar to the neck
|
|
opening and so on.
|
|
|
|
For all of these situations where you have to create curved seams with matching
|
|
length, it's impossible to get it right from the first attempt.
|
|
|
|
Instead, we try, and then course-correct until we get it right, or close enough.
|
|
|
|
This pattern is rather common, and we will unpack an example from Bent below.
|
|
|
|
Before we dive in, here's a few things to keep in mind:
|
|
|
|
- In JavaScript, you can create a function within your function and call it
|
|
- Bent extends Brian which sets both the `frontArmholeLength` and `backArmholeLength` values in the store with the length of those seams
|
|
- We need to match the length of the sleevecap + sleeve cap ease to the length of the front and back armhole
|
|
|
|
Here's how you can handle this in code:
|
|
|
|
- We create a method that does the actual drafting of our sleevecap
|
|
- We use a `tweak` value to influence the process, we start with a value of `1`
|
|
- We check the length after every attempt, and adjust the `tweak` value
|
|
|
|
```js
|
|
export const partName = (part) {
|
|
let { Path, paths, points, store, options } = part.shorthand()
|
|
|
|
// we'll call this function repeatedly until it gets it right
|
|
function draftSleeve(part, tweak) {
|
|
// Sleeve frame
|
|
points.top = new Point(0, 0)
|
|
// Note the use of tweak in the line above
|
|
points.boxTopRight = points.top.shift(0, (store.get('sleevecapTarget') / 5.8) * tweak)
|
|
// ... draft sleevecap here
|
|
}
|
|
|
|
// Get values from the store, and save our own
|
|
let armholeLength = store.get('frontArmholeLength') + store.get('backArmholeLength')
|
|
let sleevecapEase = armholeLength * options.sleevecapEase
|
|
store.set('sleevecapEase', sleevecapEase)
|
|
store.set('sleevecapTarget', armholeLength + sleevecapEase)
|
|
|
|
// Initialize
|
|
// delta holds by how far we're off
|
|
let delta = 0
|
|
// runs holds our number of attempts
|
|
let runs = 0 // number of attempts
|
|
// tweak holds our tweak factor
|
|
let tweak = 1 // tweak factor
|
|
// target holds our goal
|
|
let target = store.get('sleevecapTarget')
|
|
// using a do...while loop so this runs at least once
|
|
do {
|
|
// Draft our sleevecap
|
|
draftSleeve(part, tweak)
|
|
// Increate the run count
|
|
runs++
|
|
// Re-calculate by how far we're off
|
|
delta = store.get('sleevecapLength') - target
|
|
// If we overshot, decrease the tweak factor
|
|
if (delta > 0) tweak = tweak * 0.99
|
|
// If we're short, increase the tweak factor
|
|
else tweak = tweak * 1.02
|
|
} while (Math.abs(delta) > 2 && runs < 25)
|
|
// Keep doing this until we're off by less than 2 mm or we tried 25 times
|
|
```
|
|
|
|
A few things that are important:
|
|
|
|
- We check to see how close we are by using `Math.abs(delta)` which gives us the absolute value of our delta
|
|
- We guard against an endless loop by keeping track of the runs and giving up after 25
|
|
- We multiply by `0.99` and `1.02` to respectively decrease and increase our `tweak` factor.
|
|
This asymmetric approach avoids that we end up ping-ponging around our target value and never land somewhere in the middle
|