/// <summary>
/// Find the intersection of the segment with the half-plane and throw away the result if it is contained
/// entirely in the boundary of the half-plane. The method name is a little imprecise, but it gets across the
/// basic idea.
/// </summary>
public static Segment2D IntersectWithOpenHalfPlane(this Segment2D segment, HalfPlane2D halfPlane)
{
var basePointOffset = halfPlane.GetOffsetFromBoundaryTowardInside(segment.BasePoint);
var endPointOffset = halfPlane.GetOffsetFromBoundaryTowardInside(segment.EndPoint);
var basePointIsInInterior = !(basePointOffset <= Unit.ZeroDistance);
var endPointIsInInterior = !(endPointOffset <= Unit.ZeroDistance);
if (!basePointIsInInterior && !endPointIsInInterior)
{
return(null);
}
var containsBasePointExactly = !(basePointOffset < Unit.ZeroDistance);
var containsEndPointExactly = !(endPointOffset < Unit.ZeroDistance);
if (containsBasePointExactly && containsEndPointExactly)
{
return(segment);
}
var pointOnBoundary = halfPlane.Boundary.PointIntersectionWithLine(segment.AsLine());
return
(containsBasePointExactly
? new Segment2D(segment.BasePoint, pointOnBoundary.Value)
: new Segment2D(pointOnBoundary.Value, segment.EndPoint));
}
public HalfPlane2D GetStarboardSide() => HalfPlane2D.FromDirectionAndBoundaryPoint(Direction.RotateReverseQuarterTurn(), BasePoint);
/// <summary>
/// Construct the line perpendicular to <paramref name="offsetDirection"/> through
/// <paramref name="pointOnLine"/>.
/// </summary>
public BoundaryLine2D(Direction2D offsetDirection, Point2D pointOnLine)
: this(HalfPlane2D.FromDirectionAndBoundaryPoint(offsetDirection, pointOnLine))
{
}
public HalfPlane2D GetPortSide() => HalfPlane2D.FromDirectionAndBoundaryPoint(Direction.RotateQuarterTurn(), BasePoint);
public BoundaryLine2D([NotNull] HalfPlane2D halfPlane)
{
HalfPlane = halfPlane;
}