getPointsOnCurve static method

List<LatLng> getPointsOnCurve(LatLng startLocation, LatLng endLocation)

Implementation

static List<LatLng> getPointsOnCurve(
    LatLng startLocation, LatLng endLocation) {
  // https://medium.com/better-programming/curved-lines-on-google-maps-2938bbb15f6a
  List<LatLng> path = [];
  double angle = pi / 2;
  // ignore: non_constant_identifier_names
  double SE =
      SphericalUtils.computeDistanceBetween(startLocation, endLocation) as double;
  // ignore: non_constant_identifier_names
  double ME = SE / 2.0;
  double R = ME / sin(angle / 2);
  // ignore: non_constant_identifier_names
  double MO = R * cos(angle / 2);

  double heading = SphericalUtils.computeHeading(startLocation, endLocation) as double;
  LatLng mCoordinate =
      SphericalUtils.computeOffset(startLocation, ME, heading);

  double direction =
      (startLocation.longitude - endLocation.longitude > 0) ? -1.0 : 1.0;
  double angleFromCenter = 90.0 * direction;
  LatLng oCoordinate = SphericalUtils.computeOffset(
      mCoordinate, MO, heading + angleFromCenter);

  path.add(endLocation);

  int num = 100;

  double initialHeading =
      SphericalUtils.computeHeading(oCoordinate, endLocation) as double;
  double degree = (180.0 * angle) / pi;

  for (int i = 1; i <= num; i++) {
    double step = i.toDouble() * (degree / num.toDouble());
    double heading = (-1.0) * direction;
    LatLng pointOnCurvedLine = SphericalUtils.computeOffset(
        oCoordinate, R, initialHeading + heading * step);
    path.add(pointOnCurvedLine);
  }

  path.add(startLocation);

  return path;
}