public void CycleTest()
{
var dcel = new DCEL();
var v1 = dcel.AddVertex(new DCELVertex(0, 0));
var v2 = dcel.AddVertex(new DCELVertex(10, 10));
var v3 = dcel.AddVertex(new DCELVertex(20, 0));
var e1 = dcel.AddEdge(v1, v2);
var e2 = dcel.AddEdge(v2, v3);
var e3 = dcel.AddEdge(v3, v1);
Assert.Contains(e1, DCEL.Cycle(e1));
Assert.Contains(e2, DCEL.Cycle(e1));
Assert.Contains(e3, DCEL.Cycle(e1));
Assert.Contains(e1, DCEL.Cycle(e2));
Assert.Contains(e2, DCEL.Cycle(e2));
Assert.Contains(e3, DCEL.Cycle(e2));
Assert.Contains(e1, DCEL.Cycle(e3));
Assert.Contains(e2, DCEL.Cycle(e3));
Assert.Contains(e3, DCEL.Cycle(e3));
}
/// <summary>
/// Returns a halfedge of the leftmost middle face.
/// </summary>
/// <param name="m_dcel"></param>
/// <param name="m_dualLines"></param>
/// <returns></returns>
private static HalfEdge LeftMostMiddleHalfEdge(DCEL m_dcel, IEnumerable <Line> m_dualLines)
{
var bbox = m_dcel.InitBoundingBox.Value;
// get all intersections with left line of bounding box
var leftLine = new Line(new Vector2(bbox.xMin, bbox.yMin), new Vector2(bbox.xMin, bbox.yMax));
var intersections = m_dualLines
.Where(l => !l.IsVertical)
.Select(l => leftLine.Intersect(l).Value)
.ToList();
// sort on y value
intersections.Sort((v1, v2) => v1.y.CompareTo(v2.y));
// find edge between middle intersections
var middleIntersectBot = intersections[intersections.Count / 2 - 1];
var middleIntersectTop = intersections[intersections.Count / 2];
var edgeInterval = new FloatInterval(middleIntersectBot.y, middleIntersectTop.y);
// get corresponding halfedge in dcel
HalfEdge workingEdge;
if (bbox.yMin < edgeInterval.Min && bbox.yMax > edgeInterval.Max)
{
// both intersections contained on left segment of bounding box
workingEdge = DCEL.Cycle(m_dcel.OuterFace.InnerComponents[0])
.FirstOrDefault(e => e.From.Pos.x == bbox.xMin &&
edgeInterval.ContainsEpsilon(e.From.Pos.y) &&
edgeInterval.ContainsEpsilon(e.To.Pos.y));
}
else if (bbox.yMin >= edgeInterval.Min)
{
// bottom intersection lies below left segment
// find halfedge pointing to bottom left corner
workingEdge = DCEL.Cycle(m_dcel.OuterFace.InnerComponents[0])
.FirstOrDefault(e => MathUtil.Equals(e.From.Pos, new Vector2(bbox.xMin, bbox.yMin)));
// traverse outer cycle until we find line with the corresponding bottom intersection
while (workingEdge.Twin.Prev.Segment.Line.IsVertical ||
!MathUtil.EqualsEps(workingEdge.Twin.Prev.Segment.Line.Intersect(leftLine).Value, middleIntersectBot))
{
workingEdge = workingEdge.Next;
}
}
else
{
// top intersection lies above left segment
// find halfedge pointing away from top left corner
workingEdge = DCEL.Cycle(m_dcel.OuterFace.InnerComponents[0])
.FirstOrDefault(e => MathUtil.Equals(e.To.Pos, new Vector2(bbox.xMin, bbox.yMax)));
// traverse outer cycle until we find line with the corresponding top intersection
while (workingEdge.Twin.Next.Segment.Line.IsVertical ||
!MathUtil.EqualsEps(workingEdge.Twin.Next.Segment.Line.Intersect(leftLine).Value, middleIntersectTop))
{
workingEdge = workingEdge.Prev;
}
}
// middle edge should always exist
if (workingEdge == null)
{
throw new GeomException("working edge not found");
}
// return twin (edge of middle face, not outer face)
return(workingEdge.Twin);
}