interpolate static method
Returns the LatLng which lies the given fraction of the way between the origin LatLng and the destination LatLng. @param from The LatLng from which to start. @param to The LatLng toward which to travel. @param fraction A fraction of the distance to travel. @return The interpolated LatLng.
Implementation
static ILatLng interpolate(ILatLng from, ILatLng to, num fraction) {
if (from.isEmpty) return to;
final fromLat = from.latitude.radians;
final fromLng = from.longitude.radians;
final toLat = to.latitude.radians;
final toLng = to.longitude.radians;
final cosFromLat = math.cos(fromLat);
final cosToLat = math.cos(toLat);
// Computes Spherical interpolation coefficients.
final angle = computeAngleBetween(from, to);
final sinAngle = math.sin(angle);
if (sinAngle < 1E-6) {
return LatLngInfo(
from.latitude + fraction * (to.latitude - from.latitude),
from.longitude + fraction * (to.longitude - from.longitude),
from.markerId,
);
}
final a = math.sin((1 - fraction) * angle) / sinAngle;
final b = math.sin(fraction * angle) / sinAngle;
// Converts from polar to vector and interpolate.
final x = a * cosFromLat * math.cos(fromLng) + b * cosToLat * math.cos(toLng);
final y = a * cosFromLat * math.sin(fromLng) + b * cosToLat * math.sin(toLng);
final z = a * math.sin(fromLat) + b * math.sin(toLat);
// Converts interpolated vector back to polar.
final lat = math.atan2(z, math.sqrt(x * x + y * y));
final lng = math.atan2(y, x);
return LatLngInfo(
lat.degrees,
lng.degrees,
from.markerId,
ripple: from.ripple,
);
}