utils.curveIntersectsY()

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

warning

This function can sometimes fail to find intersections in some curves due to a limitation in an underlying Bézier library. Please see Bug #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

Preview

Code

({ 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
}

X-Ray

A Utils.curveIntersectY() example

Notes

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