Path.angleAt()

The Path.angleAt() method returns the (tangent) angle of a path at a specific point.

If the given point is a sharp corner, this method prefers returning the angle directly before the corner.

If the given point does not lie (approximately) on the path, this method returns false.

Signature

number|false path.angleAt(Point point)

Example

预览

代码

({ Point, points, Path, paths, snippets, Snippet, 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.D = new Point(50, 80)
  points.DCp1 = new Point(70, 30)

  paths.demo = new Path()
    .move(points.D)
    .curve(points.DCp1, points.DCp1, points.C)
    .curve(points.CCp1, points.BCp2, points.B)
    .line(points.A)

  points.testPoint = paths.demo.shiftFractionAlong(0.55)
  snippets.point = new Snippet("notch", points.testPoint)

  let angle = paths.demo.angleAt(points.testPoint)
  //draw a tangent path
  paths.tangent = new Path()
    .move(points.testPoint.shift(angle, -30))
    .line(points.testPoint.shift(angle, 30))
    .attr("class", "lining dashed")

  return part
}

透视

Example of the Path.angleAt() method

Notes

Keep in mind that calculations with 贝塞尔曲线 are often approximations.