private void DrawConvexHull(PointD[] points)
{
const double radius = 4.0;
// generate new random point set if desired
if (points == null)
{
Size scale = new Size(OutputBox.Width - 4 * radius, OutputBox.Height - 4 * radius);
int count = MersenneTwister.Default.Next(4, 40);
RectD bounds = new RectD(2 * radius, 2 * radius, scale.Width, scale.Height);
points = GeoAlgorithms.RandomPoints(
count, bounds, new PointDComparerY(), 2 * radius);
}
_points = points;
PointD[] polygon = GeoAlgorithms.ConvexHull(points);
OutputBox.Children.Clear();
// draw hull vertices filled, other points hollow
for (int i = 0; i < points.Length; i++)
{
bool isVertex = polygon.Contains(points[i]);
var circle = new Ellipse()
{
Width = 2 * radius, Height = 2 * radius,
Stroke = Brushes.Black,
Fill = isVertex ? Brushes.Black : null
};
Canvas.SetLeft(circle, points[i].X - radius);
Canvas.SetTop(circle, points[i].Y - radius);
OutputBox.Children.Add(circle);
}
// draw edges of convex hull
OutputBox.Children.Add(new Polygon()
{
Points = polygon.ToWpfPoints(),
Stroke = Brushes.Red
});
}
public void ConvexHull()
{
PointD p0 = new PointD(0, 0), p1 = new PointD(1, 1), p2 = new PointD(2, 0);
CollectionAssert.AreEqual(new[] { p0 }, GeoAlgorithms.ConvexHull(p0));
CollectionAssert.AreEqual(new[] { p0 }, GeoAlgorithms.ConvexHull(p0, p0));
CollectionAssert.AreEqual(new[] { p0 }, GeoAlgorithms.ConvexHull(p0, p0, p0));
CollectionAssert.AreEqual(new[] { p0, p1 }, GeoAlgorithms.ConvexHull(p0, p1));
CollectionAssert.AreEqual(new[] { p1, p0 }, GeoAlgorithms.ConvexHull(p0, p1, p0));
CollectionAssert.AreEqual(new[] { p1, p0 }, GeoAlgorithms.ConvexHull(p0, p0, p1));
CollectionAssert.AreEqual(new[] { p1, p0 }, GeoAlgorithms.ConvexHull(p0, p1, p1));
CollectionAssert.AreEqual(new[] { p1, p2, p0 }, GeoAlgorithms.ConvexHull(p0, p1, p2));
CollectionAssert.AreEqual(new[] { p1, p2, p0 }, GeoAlgorithms.ConvexHull(p1, p0, p2));
PointD p3 = new PointD(1, 0);
CollectionAssert.AreEqual(new[] { p1, p2, p0 }, GeoAlgorithms.ConvexHull(p3, p1, p0, p2));
}