/// <summary>
/// Partitions a polygon by triangles.
/// </summary>
public void Compute()
{
this.result = new List <Coordinate[]>();
List <Coordinate> shell = new List <Coordinate>(this.Source);
List <Coordinate> nextShell = new List <Coordinate>(this.Source);
Coordinate[] triangle;
Int32 coordinateCount = shell.Count - 1;
Int32 coordinateIndex = 1;
while (shell.Count != 4)
{
Coordinate centroid = LineAlgorithms.Centroid(shell[(shell.Count + coordinateIndex - 1) % coordinateCount], shell[(shell.Count + coordinateIndex + 1) % coordinateCount], this.PrecisionModel);
nextShell.Remove(nextShell[coordinateIndex]);
if (!WindingNumberAlgorithm.InExterior(shell, centroid, this.PrecisionModel) && !ShamosHoeyAlgorithm.Intersects(nextShell, this.PrecisionModel))
{
triangle = new Coordinate[3]
{
shell[(coordinateCount + coordinateIndex - 1) % coordinateCount],
shell[coordinateIndex],
shell[(coordinateCount + coordinateIndex + 1) % coordinateCount]
};
this.result.Add(triangle);
shell.Remove(shell[coordinateIndex]);
coordinateIndex = 1;
coordinateCount--;
}
else
{
coordinateIndex = (coordinateIndex + 1) % (shell.Count - 1);
nextShell = new List <Coordinate>(shell);
}
}
triangle = new Coordinate[3] {
shell[0], shell[1], shell[2]
};
this.result.Add(triangle);
this.hasResult = true;
}
/// <summary>
/// Determines whether the specified polygon is valid.
/// </summary>
/// <param name="shell">The coordinates of the polygon shell.</param>
/// <param name="holes">The coordinates of the polygon holes.</param>
/// <param name="validateIntersections">A value indicating whether to validate for intersections.</param>
/// <param name="precisionModel">The precision model.</param>
/// <returns><c>true</c> if the polygon is valid; otherwise false.</returns>
/// <exception cref="System.ArgumentNullException">The shell is null.</exception>
public static Boolean IsValid(IEnumerable <Coordinate> shell, IEnumerable <IEnumerable <Coordinate> > holes, Boolean validateIntersections, PrecisionModel precisionModel)
{
if (shell == null)
{
throw new ArgumentNullException(nameof(shell));
}
if (precisionModel == null)
{
precisionModel = PrecisionModel.Default;
}
// shell and holes existence
IEnumerator <Coordinate> shellEnumerator = shell.GetEnumerator();
if (!shellEnumerator.MoveNext())
{
// shell has no coordinates
if (holes == null)
{
return(true);
}
return(holes.Any(hole => holes.AnyElement()));
}
Int32 count = 1;
Coordinate first = shellEnumerator.Current, previous = first, current = first;
if (first == null || !first.IsValid)
{
return(false);
}
while (shellEnumerator.MoveNext())
{
current = shellEnumerator.Current;
if (current == null || !current.IsValid || current.Z != first.Z || precisionModel.AreEqual(current, previous))
{
return(false);
}
previous = current;
count++;
}
if (count < 4 || !precisionModel.AreEqual(first, current))
{
return(false);
}
List <IEnumerable <Coordinate> > ringList = new List <IEnumerable <Coordinate> >();
ringList.Add(shell);
// holes
if (holes != null)
{
foreach (IEnumerable <Coordinate> hole in holes)
{
if (hole == null)
{
continue;
}
IEnumerator <Coordinate> holeEnumerator = hole.GetEnumerator();
if (!holeEnumerator.MoveNext())
{
continue;
}
count = 1;
first = holeEnumerator.Current;
if (first == null || !first.IsValid)
{
return(false);
}
while (holeEnumerator.MoveNext())
{
current = holeEnumerator.Current;
if (current == null || !current.IsValid || current.Z != first.Z || precisionModel.AreEqual(current, previous))
{
return(false);
}
previous = current;
count++;
}
if (count < 4 || !precisionModel.AreEqual(first, current))
{
return(false);
}
ringList.Add(hole);
}
}
// check for any intersection
if (validateIntersections && ShamosHoeyAlgorithm.Intersects(ringList, precisionModel))
{
return(false);
}
return(true);
}