LineSegment.OrientationIndex returns a wrong value

[tohidemyname]

The code is as follows:

public int OrientationIndex(LineSegment seg) { int orient0 = (int)Orientation.Index(_p0, _p1, seg._p0); int orient1 = (int)Orientation.Index(_p0, _p1, seg._p1); // this handles the case where the points are Curve or collinear if (orient0 >= 0 && orient1 >= 0) return Math.Max(orient0, orient1); // this handles the case where the points are R or collinear if (orient0 <= 0 && orient1 <= 0) return Math.Max(orient0, orient1); //Bug // points lie on opposite sides ==> indeterminate orientation return 0; }

This bug line should be fixed to:

if (orient0 <= 0 && orient1 <= 0) return Math.Min(orient0, orient1);

JTS fixed a similar bug: locationtech/jts#914
libgeos/geos#699

[FObermaier]

The PR you are referring to has been adressed:

NetTopologySuite/src/NetTopologySuite/Geometries/LineSegment.cs

Lines 163 to 175 in d04ddd7

	public int OrientationIndex(LineSegment seg)
	{
	int orient0 = (int)Orientation.Index(_p0, _p1, seg._p0);
	int orient1 = (int)Orientation.Index(_p0, _p1, seg._p1);
	// this handles the case where the points are L or collinear
	if (orient0 >= 0 && orient1 >= 0)
	return Math.Max(orient0, orient1);
	// this handles the case where the points are R or collinear
	if (orient0 <= 0 && orient1 <= 0)
	return Math.Min(orient0, orient1);
	// points lie on opposite sides ==> indeterminate orientation
	return 0;
	}

Unless you provide more information about your failure case there is nothing we can do.