freesewing/sites/dev/docs/tutorials/pattern-design/part2/avoiding-overlap/readme.mdx

---
title: Avoiding overlap
order: 92
---

While we've only drawn the end of one strap, it's pretty obvious they overlap,
which makes it impossible to cut out, so we're going to have to address
that.

Specifically, we're going to rotate our strap out of the way until it no longer overlaps.
The rest of our bib should stay as it is, so let's start by making a list of points we need
to rotate.

However, there is a catch. 

## Macros and auto-generated IDs
We have used the `round` macro to help us round the corners
of our strap, and it added a bunch of auto-generated points to our pattern. We need to
rotate these points too, but what are their names?

A macro will return the names of the things it created. So far, we have not captured
that return value, but if we did, it would look like this:

```mjs
{
  "tipRightTop": {
    "points": {
      "start": "__macro_@freesewing/plugin-round_tipRightTop_start",
      "cp1": "__macro_@freesewing/plugin-round_tipRightTop_cp1",
      "cp2": "__macro_@freesewing/plugin-round_tipRightTop_cp2",
      "end": "__macro_@freesewing/plugin-round_tipRightTop_end"
    },
    "paths": {
      "path": "__macro_@freesewing/plugin-round_tipRightTop_path"
    }
  },
  "tipRightBottom": {
    "points": {
      "start": "__macro_@freesewing/plugin-round_tipRightBottom_start",
      "cp1": "__macro_@freesewing/plugin-round_tipRightBottom_cp1",
      "cp2": "__macro_@freesewing/plugin-round_tipRightBottom_cp2",
      "end": "__macro_@freesewing/plugin-round_tipRightBottom_end"
    },
    "paths": {
      "path": "__macro_@freesewing/plugin-round_tipRightBottom_path"
    }
  }
}
```

Those names aren't very handy to remember. So I will rewrite this code a bit to
we'll capture these return values from the `round` macros and create 
easy-to-remember points from them:

<Example tutorial caption="It looks the same as before, but now those macro points are accessible to us">
```design/src/bib.mjs
function draftBib({
  Path,
  Point,
  paths,
  points,
  measurements,
  options,
// highlight-start
  utils,
// highlight-end
  macro,
  part,
}) {

  /*
   * Construct the quarter neck opening
   */
  let tweak = 1
  let target = (measurements.head * options.neckRatio) /4
  let delta
  do {
    points.right = new Point(
      tweak * measurements.head / 10, 
      0
    )
    points.bottom = new Point(
      0, 
      tweak * measurements.head / 12
    )
  
    points.rightCp1 = points.right.shift(
      90, 
      points.bottom.dy(points.right) / 2
    )
    points.bottomCp2 = points.bottom.shift(
      0, 
      points.bottom.dx(points.right) / 2
    )
  
    paths.quarterNeck = new Path()
      .move(points.right)
      .curve(
        points.rightCp1, 
        points.bottomCp2, 
        points.bottom
      )
      .hide()

    delta = paths.quarterNeck.length() - target
    if (delta > 0) tweak = tweak * 0.99
    else tweak = tweak * 1.02
  } while (Math.abs(delta) > 1)

  /*
   * Construct the complete neck opening
   */
  points.rightCp2 = points.rightCp1.flipY()
  points.bottomCp1 = points.bottomCp2.flipX()
  points.left = points.right.flipX()
  points.leftCp1 = points.rightCp2.flipX()
  points.leftCp2 = points.rightCp1.flipX()
  points.top = points.bottom.flipY()
  points.topCp1 = points.bottomCp2.flipY()
  points.topCp2 = points.bottomCp1.flipY()

  paths.neck = new Path()
    .move(points.top)
    .curve(points.topCp2, points.leftCp1, points.left)
    .curve(points.leftCp2, points.bottomCp1, points.bottom)
    .curve(points.bottomCp2, points.rightCp1, points.right)
    .curve(points.rightCp2, points.topCp1, points.top)
    .close()
    .addClass('fabric')

  /*
   * Drawing the bib outline
   */
  const width = measurements.head * options.widthRatio
  const length = measurements.head * options.lengthRatio

  points.topLeft = new Point(
    width / -2,
    points.top.y - (width / 2 - points.right.x)
  )
  points.topRight = points.topLeft.shift(0, width)
  points.bottomLeft = points.topLeft.shift(-90, length)
  points.bottomRight = points.topRight.shift(-90, length)

  /*
   * Shape the straps
   */
  points.edgeLeft = new Point(points.topLeft.x, points.left.y)
  points.edgeRight = new Point(points.topRight.x, points.right.y)
  points.edgeTop = new Point(0, points.topLeft.y)

  points.edgeLeftCp = points.edgeLeft.shiftFractionTowards(points.topLeft, 0.5)
  points.edgeRightCp = points.edgeLeftCp.flipX()
  points.edgeTopLeftCp = points.edgeTop.shiftFractionTowards(
    points.topLeft,
    0.5
  )
  points.edgeTopRightCp = points.edgeTopLeftCp.flipX()

  // Round the straps
  const strap = points.edgeTop.dy(points.top)

  points.tipRight = points.edgeTop.translate(strap / 2, strap / 2)
  points.tipRightTop = new Point(points.tipRight.x, points.edgeTop.y)
  points.tipRightBottom = new Point(points.tipRight.x, points.top.y)

  // highlight-start
  /*
   * Macros will return the auto-generated IDs
   */
  const ids1 = {
    tipRightTop: macro("round", {
      id: "tipRightTop",
      from: points.edgeTop,
      to: points.tipRight,
      via: points.tipRightTop,
      hide: false
    }),
    tipRightBottom: macro("round", {
      id: "tipRightBottom",
      from: points.tipRight,
      to: points.top,
      via: points.tipRightBottom,
      hide: false
    })
  }

  /*
   * Create points from them with easy names
   */
  for (const side in ids1) {
    for (const id of ['start', 'cp1', 'cp2', 'end']) {
      points[`${side}${utils.capitalize(id)}`] = points[ids1[side].points[id]].copy()
    }
  }
  // highlight-end
  
   /*
   * Now, adapt our `rect` path so it's no longer a rectangle:
   */
  paths.rect = new Path()
    .move(points.edgeTop)
    .curve(points.edgeTopLeftCp, points.edgeLeftCp, points.edgeLeft)
    .line(points.bottomLeft)
    .line(points.bottomRight)
    .line(points.edgeRight)
    .curve(points.edgeRightCp, points.edgeTopRightCp, points.edgeTop)
    .close()

  return part
}
```
</Example>

Once we have our list of points to rotate, we can rotate them. How far? Until the strap no longer overlaps.

<Example tutorial caption="It is looking pretty wonky now, but we'll deal with that next">
```design/src/bib.mjs
function draftBib({
  Path,
  Point,
  paths,
  points,
  measurements,
  options,
  utils,
  macro,
  part,
}) {

  /*
   * Construct the quarter neck opening
   */
  let tweak = 1
  let target = (measurements.head * options.neckRatio) /4
  let delta
  do {
    points.right = new Point(
      tweak * measurements.head / 10, 
      0
    )
    points.bottom = new Point(
      0, 
      tweak * measurements.head / 12
    )
  
    points.rightCp1 = points.right.shift(
      90, 
      points.bottom.dy(points.right) / 2
    )
    points.bottomCp2 = points.bottom.shift(
      0, 
      points.bottom.dx(points.right) / 2
    )
  
    paths.quarterNeck = new Path()
      .move(points.right)
      .curve(
        points.rightCp1, 
        points.bottomCp2, 
        points.bottom
      )
      .hide()

      delta = paths.quarterNeck.length() - target
      if (delta > 0) tweak = tweak * 0.99
      else tweak = tweak * 1.02
    } while (Math.abs(delta) > 1)
  
  /*
   * Construct the complete neck opening
   */
  points.rightCp2 = points.rightCp1.flipY()
  points.bottomCp1 = points.bottomCp2.flipX()
  points.left = points.right.flipX()
  points.leftCp1 = points.rightCp2.flipX()
  points.leftCp2 = points.rightCp1.flipX()
  points.top = points.bottom.flipY()
  points.topCp1 = points.bottomCp2.flipY()
  points.topCp2 = points.bottomCp1.flipY()

  paths.neck = new Path()
    .move(points.top)
    .curve(points.topCp2, points.leftCp1, points.left)
    .curve(points.leftCp2, points.bottomCp1, points.bottom)
    .curve(points.bottomCp2, points.rightCp1, points.right)
    .curve(points.rightCp2, points.topCp1, points.top)
    .close()
    .addClass('fabric')

  // Drawing the bib outline
  const width = measurements.head * options.widthRatio
  const length = measurements.head * options.lengthRatio

  points.topLeft = new Point(
    width / -2,
    points.top.y - (width / 2 - points.right.x)
  )
  points.topRight = points.topLeft.shift(0, width)
  points.bottomLeft = points.topLeft.shift(-90, length)
  points.bottomRight = points.topRight.shift(-90, length)

  /*
   * Shape the straps
   */
  points.edgeLeft = new Point(points.topLeft.x, points.left.y)
  points.edgeRight = new Point(points.topRight.x, points.right.y)
  points.edgeTop = new Point(0, points.topLeft.y)

  points.edgeLeftCp = points.edgeLeft.shiftFractionTowards(points.topLeft, 0.5)
  points.edgeRightCp = points.edgeLeftCp.flipX()
  points.edgeTopLeftCp = points.edgeTop.shiftFractionTowards(
    points.topLeft,
    0.5
  )
  points.edgeTopRightCp = points.edgeTopLeftCp.flipX()

  // Round the straps
  const strap = points.edgeTop.dy(points.top)

  points.tipRight = points.edgeTop.translate(strap / 2, strap / 2)
  points.tipRightTop = new Point(points.tipRight.x, points.edgeTop.y)
  points.tipRightBottom = new Point(points.tipRight.x, points.top.y)

  /*
   * Macros will return the auto-generated IDs
   */
  const ids1 = {
    tipRightTop: macro("round", {
      id: "tipRightTop",
      from: points.edgeTop,
      to: points.tipRight,
      via: points.tipRightTop,
      hide: false
    }),
    tipRightBottom: macro("round", {
      id: "tipRightBottom",
      from: points.tipRight,
      to: points.top,
      via: points.tipRightBottom,
      hide: false
    })
  }

  /*
   * Create points from them with easy names
   */
  for (const side in ids1) {
    for (const id of ['start', 'cp1', 'cp2', 'end']) {
      points[`${side}${utils.capitalize(id)}`] = points[ids1[side].points[id]].copy()
    }
  }

  // highlight-start
  /*
   * This is the list of points we need to rotate
   * to move our strap out of the way
   */
  const rotateThese = [
    "edgeTopLeftCp",
    "edgeTop",
    "tipRight",
    "tipRightTop",
    "tipRightTopStart",
    "tipRightTopCp1",
    "tipRightTopCp2",
    "tipRightTopEnd",
    "tipRightBottomStart",
    "tipRightBottomCp1",
    "tipRightBottomCp2",
    "tipRightBottomEnd",
    "tipRightBottom",
    "top",
    "topCp2"
  ]
  /*
   * We're rotating all the points in
   * the `rotateThese` array around
   * the `edgeLeft` point.
   *
   * We're using increments of 1 degree
   * until the `tipRightBottomStart` point
   * is 1 mm beyond the center of our bib.
   */
  while (points.tipRightBottomStart.x > -1) {
    for (const p of rotateThese) points[p] = points[p].rotate(1, points.edgeLeft)
  }

  /*
   * This is not needed
   * we are merely adding it to show
   * what the rotated path looks like
   */
  macro("round", {
    id: "showRightTop",
    from: points.edgeTop,
    to: points.tipRight,
    via: points.tipRightTop,
    hide: false,
    classes: 'contrast dotted',
  })
  macro("round", {
    id: "showRightBottom",
    from: points.tipRight,
    to: points.top,
    via: points.tipRightBottom,
    hide: false,
    classes: 'contrast dotted',
  })
  // highlight-end
  /*
   * Now, adapt our `rect` path so it's no longer a rectangle:
   */
  paths.rect = new Path()
    .move(points.edgeTop)
    .curve(points.edgeTopLeftCp, points.edgeLeftCp, points.edgeLeft)
    .line(points.bottomLeft)
    .line(points.bottomRight)
    .line(points.edgeRight)
    .curve(points.edgeRightCp, points.edgeTopRightCp, points.edgeTop)
    .close()

  return part
}
```
</Example>