lineSegmentIntersection method

double? lineSegmentIntersection(LineSegment segment)

Returns where (length wise) on the ray that the ray intersects the LineSegment or null if there is no intersection.

A ray that is parallel and overlapping with the segment is considered to not intersect. This is due to that a single intersection point can't be determined and that a LineSegment is almost always connected to another line segment which will get the intersection on one of its ends instead.

Implementation

double? lineSegmentIntersection(LineSegment segment) {
  _v1
    ..setFrom(origin)
    ..sub(segment.from);
  _v2
    ..setFrom(segment.to)
    ..sub(segment.from);
  _v3.setValues(-direction.y, direction.x);

  final dot = _v2.dot(_v3);
  final t1 = _v2.cross(_v1) / dot;
  final t2 = _v1.dot(_v3) / dot;
  if (t1 >= 0 && t2 >= 0 && t2 <= 1) {
    return t1;
  }
  return null;
}