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freesewing/sites/dev/docs/reference/api/path/intersectsbeam
Jonathan Haas 4b83212f41 Fix and improve path intersection methods
- Add path.intersectsBeam() method
- Add utils.beamIntersectsLine() method
- Simplify calculation and improve precision on beam intersections
- Document return types properly
- beamIntersectsCurve now uses the proper function from Bezier library instead of emulating it by constructing a huge line
- docs: path.intersect... methods never return false, they simply return an empty array in case of no intersection
2024-10-03 11:37:55 +02:00
..
readme.mdx Fix and improve path intersection methods 2024-10-03 11:37:55 +02:00

---
title: Path.intersectsBeam()
---

The `Path.intersectsBeam()` method returns the Point object(s) where the path
intersects with an endless line (beam).

:::warning

This method can sometimes fail to find intersections in some curves
due to a limitation in an underlying Bézier library.
Please see [Bug #3367](https://github.com/freesewing/freesewing/issues/3367)
for more information.

:::

## Signature

```js
array path.intersectsBeam(Point a, Point b)
```

<Example caption="Example of the Path.intersectsBeam() method">

```js
;({ Point, points, Path, paths, snippets, Snippet, getId, part }) => {
  points.A = new Point(45, 60)
  points.B = new Point(10, 30)
  points.BCp2 = new Point(40, 20)
  points.C = new Point(90, 30)
  points.CCp1 = new Point(50, -30)

  points.beamA = new Point(55, 30)
  points.beamB = new Point(0, 55)

  paths.demo1 = new Path().move(points.A).line(points.B).curve(points.BCp2, points.CCp1, points.C)

  paths.beam = new Path().move(points.beamA).line(points.beamB).addClass('dashed')

  for (let p of paths.demo1.intersectsBeam(points.beamA, points.beamB)) {
    snippets[getId()] = new Snippet('notch', p)
  }

  return part
}
```

</Example>

## Notes

This method works similar to `path.intersectsX(...)` and `path.intersectsY(...)`,
but here the intersecting beam doesn't have to be horizontally or vertically.

If you need intersections with a limited line instead of a beam,
use something like `path.intersects(new Path.move(pointA).line(pointB))` instead.