/// <summary>
/// Computes the planar orientation of a polygon.
/// </summary>
/// <param name="shell">The coordinates of the polygon shell.</param>
/// <param name="precisionModel">The precision model.</param>
/// <returns>The orientation of the polygon. If the polygon is invalid <see cref="AEGIS.Orientation.Undefined" /> is returned.</returns>
/// <exception cref="System.ArgumentNullException">The shell is null.</exception>
public static Orientation Orientation(IEnumerable <Coordinate> shell, PrecisionModel precisionModel)
{
if (shell == null)
{
throw new ArgumentNullException(nameof(shell));
}
// check for polygon properties
IEnumerator <Coordinate> enumerator = shell.GetEnumerator();
Double sum = 0;
Int32 count = 1;
if (!enumerator.MoveNext())
{
return(AEGIS.Orientation.Undefined);
}
Coordinate first = enumerator.Current, previous = first, current = first;
while (enumerator.MoveNext())
{
current = enumerator.Current;
sum += (current.X - previous.X) * (current.Y + previous.Y);
count++;
previous = current;
}
if (count < 3)
{
return(AEGIS.Orientation.Undefined);
}
if (precisionModel == null)
{
precisionModel = PrecisionModel.Default;
}
if (!precisionModel.AreEqual(first, current))
{
sum += (first.X - current.X) * (first.Y + current.Y);
}
if (Math.Abs(sum) <= precisionModel.Tolerance(shell))
{
return(AEGIS.Orientation.Collinear);
}
return((sum > 0) ? AEGIS.Orientation.Clockwise : AEGIS.Orientation.Counterclockwise);
}
/// <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);
}