freesewing/packages/jaeger/src/backbase.js

import { calculateRatios, backSideBoundary } from "./shared";

export default function(part) {
  calculateRatios(part);
  let { store, points, measurements, options, Point, paths, Path } = part.shorthand();

  /**
   * Shaping the back seam
   */

  points.cbChest = new Point(0, points.armholePitchCp1.y);
  if (options.centerBackDart > 0) {
    points.cbChestCp1 = points.cbChest.shiftFractionTowards(points.cbNeck, 0.5);
    points.cbNeck = points.cbNeck.shift(0, measurements.chestCircumference * options.centerBackDart);
  }
  points.cbChestCp2 = points.cbChest.shift(-90, points.cbChest.dy(points.cbWaist)/3);
  points.cbWaist = points.cbWaist.shift(0, store.get("waistReduction") * options.reduceWaistStandardFraction);
  points.cbWaistCp1 = points.cbWaist.shift(90, points.cbChest.dy(points.cbWaist)/3);
  points.cbHips = points.cbHips.shift(0, store.get("hipsReduction") * options.reduceHipsStandardFraction);
  points.cbHem = points.cbHem.shift(0, store.get("hipsReduction") * options.reduceHipsStandardFraction);
  points.cbWaistCp2 = points.cbWaist.shift(-90, points.cbWaist.dy(points.cbHips)/3);
  points.cbHipsCp1 = points.cbHips.shift(90, points.cbWaist.dy(points.cbHips)/3);

  /**
   * Shaping the side seam
   */

  backSideBoundary(part);

  // Divide reduction by 4: two side panels x two sides per panel = 4
  points.waist = points.bsWaist.shift(180, store.get("waistReduction") * options.reduceWaistStandardFraction);
  points.waistCp2 = points.waist.shift(90, points.cbChest.dy(points.waist)/3);
  points.hips = points.bsHips.shift(180, store.get("hipsReduction") * options.reduceHipsStandardFraction);
  points.waistCp1 = points.waist.shift(-90, points.waist.dy(points.hips)/3);
  points.hipsCp2 = points.hips.shift(90, points.waist.dy(points.hips)/3);
  points.hem = new Point(points.hips.x, points.hem.y);

  // Store length of back collar
  store.set("backCollarLength", new Path()
    .move(points.cbNeck)
    ._curve(points.neckCp2, points.neck)
    .length()
  );

  // Paths
  paths.cb = new Path().move(points.cbNeck);
  if (options.centerBackDart > 0)
    paths.cb._curve(points.cbChestCp1, points.cbChest);
  else paths.cb.line(points.cbChest);

  paths.cb
    .curve(points.cbChestCp2, points.cbWaistCp1, points.cbWaist)
    .curve(points.cbWaistCp2, points.cbHipsCp1, points.cbHips)
    .line(points.cbHem)
    .attr("class", "stroke-xl lining")

  paths.bss = new Path()
    .move(points.armholeHollow)
    .curve(points.bsArmholeHollowCp2, points.waistCp2, points.waist)
    .curve(points.waistCp1, points.hipsCp2, points.hips)
    .line(points.hem)
    .attr("class", "stroke-xl lining")

  return part;
}