freesewing/markdown/dev/reference/api/utils/curveintersectsy/en.md

title
utils.curveIntersectsY()

The utils.curveIntersectsY() function finds the point(s) where a curve intersects a given Y-value.

This function 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

array | Point | false utils.curveIntersectsY(
  Point start,
  Point cp1,
  Point cp2,
  Point end,
  float y)

This returns false if no intersections are found, a Point object if a single intersection is found, and an array of Point objects if multiple intersections are found.

Example

```js ({ Point, points, Path, paths, Snippet, snippets, utils, part }) => {

points.start = new Point(10, 45) points.cp1 = new Point(50, 10) points.cp2 = new Point(0, 80) points.end = new Point(110, 70)

paths.curve = new Path() .move(points.start) .curve(points.cp1, points.cp2, points.end)

for (let y of [40, 50]) { points["from" + y] = new Point(10, y) points["to" + y] = new Point(110, y) paths["line" + y] = new Path() .move(points["from" + y]) .line(points["to" + y]) .addClass("lining dashed") }

snippets.i50 = new Snippet( "notch", utils.curveIntersectsY(points.start, points.cp1, points.cp2, points.end, 50) )

for (let p of utils.curveIntersectsY( points.start, points.cp1, points.cp2, points.end, 40 )) snippets[p.x] = new Snippet("notch", p)

return part }

</Example>

## Notes

This is a low-level (and faster) variant
of [`Path.intersectsY()`](/reference/api/path/intersectsy).
Instead of a path, you describe a single curve by passing the four
points that describes it.