project method

@override Point project(double longitude, double latitude)

Projects a geographic coordinate longitude, latitude to screen coordinates.

Implementation

@override
Point project(double longitude, double latitude) {
  final lambda = toRadians(longitude - centerLon + _rotate0);
  final phi = toRadians(latitude);

  final cosLambda = math.cos(lambda);
  final sinLambda = math.sin(lambda);
  final cosPhi = math.cos(phi);
  final sinPhi = math.sin(phi);

  // Check if point is on visible hemisphere
  final cosc = math.sin(toRadians(centerLat)) * sinPhi +
      math.cos(toRadians(centerLat)) * cosPhi * cosLambda;

  if (cosc < 0) {
    // Point is on back of globe, return NaN
    return const Point(double.nan, double.nan);
  }

  final x = cosPhi * sinLambda;
  final y = math.cos(toRadians(centerLat)) * sinPhi -
      math.sin(toRadians(centerLat)) * cosPhi * cosLambda;

  return applyTransform(x, -y);
}