[bug]: Jager sleeves still have problems, though ease is fixed.

[RockerKitten]

What seems to be the problem? 🤔

Jager (and Bent) sleeves generate larger for smaller bicep measures, and smaller for larger bicep measures.
All else equal, at default ease of 15% Jager, with 20cm set for bicep circumference results in this sleeve

with the bicep measure set to 30cm this is the sleeve that is generated

and with a bicep of 40 cm this is the sleeve that is generated

Moving the bicep ease slider now correctly makes it larger for more ease, and smaller for less ease however.

Design / Plugin / Package 🧐

designs/jaeger

Additional context

I checked and Bent has the same issue.

[BenJamesBen]

The problem is that:

1. Bent's sleeve width is inversely proportional to the sleevecap height.
2. Bent's sleevecap height is proportional to the biceps circumference.
3. So, as the biceps get larger, the sleevecap gets taller and the sleeve gets narrower.

A possible solution might be for Bent to start with a baseline sleevecap height simply based on the armhole size, then decrease sleevecap height based on biceps circumference. So, a larger biceps circumference would result in a shorter sleevecap and a wider sleeve.

These values are entirely made up and probably bogus, but for example:

--- a/designs/bent/src/sleeve.mjs
+++ b/designs/bent/src/sleeve.mjs
@@ -1,7 +1,7 @@
 import { front } from '@freesewing/brian'
 
-function draftBentSleeve({ Path, paths, points, store, options, part }) {
-  function draftSleeve(part, tweak) {
+function draftBentSleeve({ Path, paths, points, store, options, part, log }) {
+  function draftSleeve(part, tweak, target) {
     let { Point, Path, points, store, options, measurements, utils } = part.shorthand()
     // Sleeve frame
     points.top = new Point(0, 0)
@@ -13,9 +13,12 @@ function draftBentSleeve({ Path, paths, points, store, options, part }) {
     )
     points.boxBottomRight = points.boxBottom.shift(0, points.boxTopRight.x)
     points.boxBottomLeft = points.boxBottomRight.flipX()
+    const bicepsConstant = 0.15
+    const baseSleeveHeight = target * options.sleevecapHeight
+    const bicepsFactor = measurements.biceps * (1 + options.bicepsEase) * bicepsConstant
     points.armCenter = points.top.shift(
       -90,
-      measurements.biceps * (1 + options.bicepsEase) * options.sleevecapHeight * tweak
+      (baseSleeveHeight - bicepsFactor * tweak)
     )
     points.armRight = points.armCenter.shift(0, points.boxTopRight.x)
     points.armLeft = points.armRight.flipX()
@@ -133,7 +136,7 @@ function draftBentSleeve({ Path, paths, points, store, options, part }) {
   let tweak = 1
   let target = store.get('sleevecapTarget')
   do {
-    draftSleeve(part, tweak)
+    draftSleeve(part, tweak, target)
     runs++
     delta = store.get('sleevecapLength') - target
     if (delta > 0) tweak = tweak * 0.99

[joostdecock]

@all-contributors please add @RockerKitten for question

[allcontributors]

@joostdecock

I've put up a pull request to add @RockerKitten! 🎉