public static Either <Null, Point2D, Segment2D> IntersectWithDisk(this Segment2D segment, Circle2D diskBoundary)
{
var lineIntersectionsWithBoundary = diskBoundary.IntersectWithLine(segment.AsLine()).ToList();
if (lineIntersectionsWithBoundary.Count == 0)
{
return(Null.Instance);
}
if (lineIntersectionsWithBoundary.Count == 1)
{
var point = lineIntersectionsWithBoundary.Single();
if (segment.Contains(point))
{
return(point);
}
return(Null.Instance);
}
var segmentDirection = segment.GetDirection();
var(baseSideIntersection, endSideIntersection) =
(lineIntersectionsWithBoundary[0], lineIntersectionsWithBoundary[1]).ReverseIf(
(lineIntersectionsWithBoundary[0].DirectionTo(lineIntersectionsWithBoundary[1])
.Value
.DotProduct(segmentDirection)
) < 0);
var clipBase =
(baseSideIntersection - segment.BasePoint).GetComponentInDirection(segmentDirection)
> Unit.ZeroDistance;
var clipEnd =
(endSideIntersection - segment.EndPoint).GetComponentInDirection(segmentDirection) < Unit.ZeroDistance;
var clippedBase = clipBase ? baseSideIntersection : segment.BasePoint;
var clippedEnd = clipEnd ? endSideIntersection : segment.EndPoint;
if (clippedBase == clippedEnd)
{
return(clipBase ? segment.EndPoint : segment.BasePoint);
}
var signedDistance = (clippedEnd - clippedBase).GetComponentInDirection(segmentDirection);
if (signedDistance > Unit.ZeroDistance)
{
return(new Segment2D(clippedBase, clippedEnd));
}
return(Null.Instance);
}
public void Property_IfSegmentsAreParallelAndIntersect_ItShouldBeAnEndPoint
(
Segment2D segment1,
Segment2D segment2
)
{
var intersection = segment1.IntersectWithSegment(segment2);
if (
segment1.GetDirection().IsParallelTo(segment2.GetDirection()) &&
intersection.Is <Point2D>(out var point2D))
{
var point = point2D.ToPoint3D();
var isEndOfOneOf = point.IsBaseOrEndPointOf(segment1.To3D()) ||
point.IsBaseOrEndPointOf(segment2.To3D());
isEndOfOneOf.Should().BeTrue();
}
}
