public static Pnt2D CutDirDir([NotNull] Pnt s0,
[NotNull] Pnt dir0,
[NotNull] Pnt s1,
[NotNull] Pnt dir1,
out double f)
/*
* (x1) (a1) (x2) (a2) (x)
* ( ) + t*( ) = ( ) + v*( ) ==> ( )
* (y1) (b1) (y2) (b2) (y)
*
* return : Point2D : lines cut each other at Point (non parallel)
* null : lines are parallel
* t = square of distance between the parallels
*/
{
Pnt p = s1 - s0;
double det = dir0.VectorProduct(dir1);
if (Math.Abs(det) > _epsi * (Math.Abs(s0.X) + Math.Abs(s1.X) +
Math.Abs(s0.Y) + Math.Abs(s1.Y)) / 1000.0)
{
f = p.VectorProduct(dir1) / det;
return((Pnt2D)(s0 + f * dir0));
}
// parallel lines
det = dir0.VectorProduct(p);
f = (det * det) / dir0.OrigDist2(2);
return(null);
}
private static bool?GetOnRightSide(
[NotNull] SegmentProxy nearestSegment, double nearestFraction,
[NotNull] SegmentProxy segmentProxy, double alongFraction,
[NotNull] IGeometry baseGeometry)
{
if (nearestSegment.PartIndex != segmentProxy.PartIndex)
{
return(null);
}
SegmentProxy from;
SegmentProxy to;
if (nearestFraction >= 1)
{
if (alongFraction > 0)
{
return(null);
}
ISegmentProxy next = nearestSegment.GetNextSegment(baseGeometry);
if (next == null)
{
return(null);
}
if (next.SegmentIndex != segmentProxy.SegmentIndex)
{
return(null);
}
from = nearestSegment;
to = segmentProxy;
}
else if (nearestFraction <= 0)
{
if (alongFraction < 1)
{
return(null);
}
ISegmentProxy next = segmentProxy.GetNextSegment(baseGeometry);
if (next == null)
{
return(null);
}
if (next.SegmentIndex != nearestSegment.SegmentIndex)
{
return(null);
}
from = segmentProxy;
to = nearestSegment;
}
else
{
// unexpected
return(null);
}
Pnt vectorFrom = from.GetEnd(as3D: false) - from.GetStart(as3D: false);
Pnt vectorTo = to.GetEnd(as3D: false) - to.GetStart(as3D: false);
bool onRightSide = vectorFrom.VectorProduct(vectorTo) > 0;
return(onRightSide);
}
