Map Your Apps: Listing 2.

Drawing an arc using a Bezier curve.

private void DrawCurve(Location start, Location finish)
{
  MapPolyline curve = new MapPolyline();
  curve.Stroke = new SolidColorBrush(Colors.Magenta);
  curve.StrokeThickness = 3.0;
  curve.StrokeDashArray = new DoubleCollection(new double[] { 5, 2 });
  curve.Opacity = 1.0;

  LocationCollection coll = new LocationCollection();

  // Compute control point
  Point p1 = myMap.LocationToViewportPoint(start);
  Point p2 = myMap.LocationToViewportPoint(finish);

  double boundingBoxHalfWidth = (p2.X - p1.X) / 2.0;
  double boundingBoxHalfHeight = (p1.Y - p2.Y) / 2.0;

  double centerX = (p1.X + p2.X) / 2.0;
  double centerY = (p1.Y + p2.Y) / 2.0;

  double xScale = 1.0;
  double yScale = 1.0;

  double controlX = centerX - (xScale * boundingBoxHalfWidth);
  double controlY = centerY - (yScale * boundingBoxHalfHeight);

  Point controlPt = new Point(controlX, controlY);
  Location controlLoc = myMap.ViewportPointToLocation(controlPt);

  // Compute intermediate Locations using the control point
  int numSegments = 31;
  doublet Delta = 1.0 / numSegments;
  for (double t = 0.0; t <= 1.0; t += tDelta) // Danger!
  {
    // x coordinate (longitudes)
    double a = (1.0 - t) * (1.0 - t) * start.Longitude;
    double b = 2.0 * (1.0 - t) * t * controlLoc.Longitude;
    double c = t * t * finish.Longitude;
    double Blon = a + b + c;

    // y coordinate (latitudes)
    a = (1.0 - t) * (1.0 - t) * start.Latitude;
    b = 2.0 * (1.0 - t) * t * controlLoc.Latitude;
    c = t * t * finish.Latitude;
    double Blat = a + b + c;

    coll.Add(new Location(Blat, Blon));
  }

  curve.Locations = coll;
  myMap.Children.Add(curve);
}

About the Author

Dr. James McCaffrey works for Microsoft Research in Redmond, Wash. He has worked on several Microsoft products including Azure and Bing. James can be reached at [email protected].

comments powered by Disqus

Featured

  • Black White Wave IMage

    New Azure AI VMs Immediately Claim Top500 Supercomputer Rankings

    Visual Studio coders who dabble in artificial intelligence projects can now take advantage of new Azure virtual machines (VMs) featuring 80 GB NVIDIA GPUs that immediately claimed four spots on the TOP500 supercomputers list, Microsoft said.

  • Colorful Night IMage

    Auto Completions Speed Up in Java on Visual Studio Code

    Java jockeys using Microsoft's Visual Studio Code editor will see faster code completions thanks to a new language server.

  • New Toolkit for Writing Visual Studio Extensions (And Where to Find Extensions)

    Microsoft details a new Extensibility Essentials toolkit for VS 2022 and explains where to find your favorite tools.

  • New TypeScript 4.5 Improves Asynchronous Programming

    TypeScript 4.5 has shipped with a new Awaited type and Promise improvements for enhancing asynchronous programming in Microsoft's popular take on JavaScript that adds statically checked types.

Upcoming Events