/// <summary>
/// Tests whether a triangular ring would be eroded completely by the given
/// buffer distance.
/// This is a precise test. It uses the fact that the inner buffer of a
/// triangle converges on the inCentre of the triangle (the point
/// equidistant from all sides). If the buffer distance is greater than the
/// distance of the inCentre from a side, the triangle will be eroded completely.
/// This test is important, since it removes a problematic case where
/// the buffer distance is slightly larger than the inCentre distance.
/// In this case the triangle buffer curve "inverts" with incorrect topology,
/// producing an incorrect hole in the buffer.
/// </summary>
/// <param name="triangleCoord"></param>
/// <param name="bufferDistance"></param>
/// <returns></returns>
private static bool IsTriangleErodedCompletely(Coordinate[] triangleCoord, double bufferDistance)
{
var tri = new Triangle(triangleCoord[0], triangleCoord[1], triangleCoord[2]);
var inCentre = tri.InCentre();
var distToCentre = CGAlgorithms.DistancePointLine(inCentre, tri.P0, tri.P1);
return distToCentre < Math.Abs(bufferDistance);
}
public static IGeometry Incentre(IGeometry g)
{
Coordinate[] pts = TrianglePts(g);
Triangle t = new Triangle(pts[0], pts[1], pts[2]);
Coordinate cc = t.InCentre();
IGeometryFactory geomFact = FunctionsUtil.GetFactoryOrDefault(g);
return geomFact.CreatePoint(cc);
}
public static IGeometry AngleBisectors(IGeometry g)
{
Coordinate[] pts = TrianglePts(g);
Triangle t = new Triangle(pts[0], pts[1], pts[2]);
Coordinate cc = t.InCentre();
IGeometryFactory geomFact = FunctionsUtil.GetFactoryOrDefault(g);
ILineString[] line = new ILineString[3];
line[0] = geomFact.CreateLineString(new[] { pts[0], cc });
line[1] = geomFact.CreateLineString(new[] { pts[1], cc });
line[2] = geomFact.CreateLineString(new[] { pts[2], cc });
return geomFact.CreateMultiLineString(line);
}