/// <summary>
/// Uses the Andrew variant of the Graham formula for calculating
/// convex hulls.
/// </summary>
/// <param name="points"></param>
/// <returns></returns>
public Point[] CalculateConvexHull(Point[] points)
{
if (points.Length < 3)
{
return(points);
}
// TODO: Implement a quicksort algorithm, and find cut off point for switching algorithms.
points = BubblesortPoints(points);
List <Point> upper = new List <Point>();
upper.Add(points[0]);
upper.Add(points[1]);
for (int i = 2; i < points.Length; i++)
{
upper.Add(points[i]);
while (upper.Count > 2 && !ExtraMath.IsRightTurn(upper[upper.Count - 3], upper[upper.Count - 2], upper[upper.Count - 1]))
{
upper.RemoveAt(upper.Count - 2);
}
}
List <Point> lower = new List <Point>();
lower.Add(points[points.Length - 1]);
lower.Add(points[points.Length - 2]);
for (int i = points.Length - 3; i >= 0; i--)
{
lower.Add(points[i]);
while (lower.Count > 2 && !ExtraMath.IsRightTurn(lower[lower.Count - 3], lower[lower.Count - 2], lower[lower.Count - 1]))
{
lower.RemoveAt(lower.Count - 2);
}
}
Point[] retPoints = new Point[upper.Count + lower.Count];
for (int i = 0; i < upper.Count; i++)
{
retPoints[i] = upper[i];
}
for (int i = 0; i < lower.Count; i++)
{
retPoints[i + upper.Count] = lower[i];
}
return(retPoints);
}
