/// <summary>
/// creates the concave hull based on the convex hull and an angle threshold
/// </summary>
/// <param name="pConvexEdges">edges of convex hull</param>
/// <param name="pPoints">the point cloud data set</param>
/// <param name="pMaxAngle">angle threshold</param>
/// <returns>list of concave hull edges</returns>
static List <tEdge> CreateConvaveHullFromConvexEdges(List <DefaultConvexFace <Vertex> > pConvexEdges, HashSet <Vertex> pPoints, double pMaxAngle)
{
//initialize arrays
List <tEdge> convexHull = new List <tEdge>();
foreach (var v in pConvexEdges)
{
convexHull.Add(new tEdge(v.Vertices[0], v.Vertices[1]));
}
List <tEdge> concaveHull = new List <tEdge>();
//iterate through convex hull until concave hull is found
while (convexHull.Count > 0)
{
//find longest edge in convex hull list
tEdge longestEdge = convexHull.MaxBy(t => t.length);
//remove longest edge from convex hull
convexHull.Remove(longestEdge);
//find nearest point
List <tEdge> edges = convexHull.Concat(concaveHull).ToList();
tVector nextPoint = FindPointWithSmallestAngle(pPoints, longestEdge, edges, pMaxAngle);
if (nextPoint == null) //if no next point found
{
concaveHull.Add(longestEdge);
continue;
}
//create edges based on nearest point
tEdge e2 = new tEdge(longestEdge.v1, nextPoint.vector);
tEdge e3 = new tEdge(longestEdge.v2, nextPoint.vector);
//check if e2 and e3 intersect
bool intersect = false;
foreach (tEdge e1 in edges)
{
if (Intersects(e2, e1) || Intersects(e3, e1))
{
intersect = true;
break;
}
}
//add e2 and e3 to List A again, if no intersection
if (intersect == false)
{
convexHull.Add(e2); convexHull.Add(e3); continue;
}
//if no concaviction found, add longest edge to concaveHull list
concaveHull.Add(longestEdge);
}
return(concaveHull);
}
/// <summary>
/// finds the point with the smallest angle from a given dataset towards an edge
/// </summary>
/// <param name="pPoints">the dataset</param>
/// <param name="pLine">the edge to calculate the angle towards</param>
/// <param name="pBoundaries">boundaries</param>
/// <param name="pMaxAngle">angle threshold</param>
/// <returns></returns>
static tVector FindPointWithSmallestAngle(HashSet <Vertex> pPoints, tEdge pLine, List <tEdge> pBoundaries, double pMaxAngle)
{
tVector bestFit = null;
Object lockObject = new object();
Parallel.ForEach(pPoints, v =>
{
//check if point is on concave hull
if (!IsPointOnConcaveHull(v, pBoundaries))
{
//calculate new potential edges
tEdge t1 = new tEdge(pLine.v1, v);
tEdge t2 = new tEdge(pLine.v2, v);
//check if local maximum < edge length
if (t1.length < pLine.length && t2.length < pLine.length)
{
//calculate the highest angle between lines and the new point
double maxAngle;
double angleA = Math.Abs(CalculateAngleBetweenTwoLines(pLine, t1));
double angleB = Math.Abs(CalculateAngleBetweenTwoLines(pLine, t2));
if (angleA > angleB)
{
maxAngle = angleA;
}
else
{
maxAngle = angleB;
}
//check if highest angle is smaller than threshold
if (maxAngle < pMaxAngle)
{
//check if bestFit has been initialized
tVector currentFit = new tVector(v, maxAngle);
lock (lockObject)
if (bestFit == null)
{
bestFit = currentFit;
}
//check if current point has a better fit
lock (lockObject)
if (currentFit.maxAngle < bestFit.maxAngle)
{
bestFit = currentFit;
}
}
}
}
});
return(bestFit);
}
public override IDerivation Visit(AlternativeSet aAlternativeSet, DerivationContext aContext)
{
for (int i = 0; i < aAlternativeSet.Count; i++)
{
IPhrase phr = aAlternativeSet.Phrases[i];
if (OmmitTerminals && phr is Terminal)
{
continue;
}
tEdge edge = addEdge(aContext, phr, aAlternativeSet.Parent);
edge.CustomAttributes = phr.IsCyclic ? GrammarGraphEdgeAttrs.IsCyclic : GrammarGraphEdgeAttrs.None;
phr.Accept(NewContext(aAlternativeSet, aContext));
}
return(null);
}
public override IDerivation Visit(Seqence aSeqence, DerivationContext aContext)
{
for (int i = 0; i < aSeqence.Count; i++)
{
IPhrase phr = aSeqence.Phrases[i];
if (OmmitTerminals && phr is Terminal)
{
continue;
}
tEdge edge = addEdge(aContext, phr, aSeqence.Parent);
edge.CustomAttributes = GrammarGraphEdgeAttrs.IsSequence
| (phr.IsCyclic ? GrammarGraphEdgeAttrs.IsCyclic : GrammarGraphEdgeAttrs.None);
phr.Accept(NewContext(aSeqence, aContext));
}
return(null);
}
/// <summary>
/// checks if two edges are intersecting
/// </summary>
/// <param name="AB">edge 1</param>
/// <param name="CD">edge 2</param>
/// <returns>true if intersects, false if not</returns>
static bool Intersects(tEdge AB, tEdge CD)
{
//http://www.codeproject.com/Tips/862988/Find-the-Intersection-Point-of-Two-Line-Segments
Vector ABs = new Vector(AB.v1.Position[0], AB.v1.Position[1]);
Vector ABe = new Vector(AB.v2.Position[0], AB.v2.Position[1]);
Vector CDs = new Vector(CD.v1.Position[0], CD.v1.Position[1]);
Vector CDe = new Vector(CD.v2.Position[0], CD.v2.Position[1]);
Vector intersection;
bool intersects = LineSegmentIntersection.LineSegementsIntersect(ABs, ABe, CDs, CDe, out intersection);
if (intersects)
{
if (intersection.Equals(ABs) || intersection.Equals(ABe) || intersection.Equals(CDs) || intersection.Equals(CDe))
{
return(false);
}
}
return(intersects);
}
public override IDerivation Visit(NonTerminal aSymbol, DerivationContext aContext)
{
tGraph graph = (aContext as BuildGraphContext).BuildingGraph;
if ((aSymbol.CycicKind & CycicKind.CyclicOrigin) > 0)
{
graph.ensureExistsNode(aSymbol.CounterName, aSymbol.Text);
graph.ensureExistsNode(aSymbol.CyclicToOccurence, aSymbol.Text);
tEdge e = graph.addEdge(aSymbol.CounterName, aSymbol.CyclicToOccurence);
if (e != null)
{
e.CustomAttributes = GrammarGraphEdgeAttrs.IsPunktir;
}
}
if (aSymbol.CycicKind == CycicKind.None ||
aSymbol.CycicKind == CycicKind.CyclicPropagated)
{
aSymbol.FindItsRule().Expand(aContext);
}
return(null);
}
/// <summary>
/// calculates the angle between two lines
/// </summary>
/// <param name="l1">line 1</param>
/// <param name="l2">line 2</param>
/// <returns>the angle between line 1 and line 2</returns>
static double CalculateAngleBetweenTwoLines(tEdge l1, tEdge l2)
{
//https://social.msdn.microsoft.com/Forums/vstudio/en-US/fa0cfeb6-70b7-4181-bc9b-fe625cd5e159/angle-between-two-lines
//Double Angle = Math.Atan2(y2-y1, x2-x1) - Math.Atan2(y4-y3,x4-x3);
return(Math.Atan2(l1.v2.Position[1] - l1.v1.Position[1], l1.v2.Position[0] - l1.v1.Position[0]) - Math.Atan2(l2.v2.Position[1] - l2.v1.Position[1], l2.v2.Position[0] - l2.v1.Position[0]));
/*
* //http://usb.unitedsb.de/topic/72776-java-winkel-zwischen-2-geraden-berechnen-wie/
* //calculate new vectors // l1.v1 == l2.v1
* Vertex P1P2 = new Vertex(l1.v2.Position[0] - l1.v1.Position[0], l1.v2.Position[1] - l1.v1.Position[1]);
* Vertex P1P3 = new Vertex(l2.v2.Position[0] - l1.v1.Position[0], l2.v2.Position[1] - l1.v1.Position[1]);
*
* //calculate length of vectors
* double norm1 = Math.Sqrt((P1P2.Position[0] * P1P2.Position[0]) + (P1P2.Position[1] * P1P2.Position[1]));
* double norm2 = Math.Sqrt((P1P3.Position[0] * P1P3.Position[0]) + (P1P3.Position[1] * P1P3.Position[1]));
*
* //scalar product
* double skpr = (P1P2.Position[0] * P1P3.Position[0]) + (P1P2.Position[1] * P1P3.Position[1]);
*
* //calc angle (radial, bogenmaß)
* double alpha = Math.Acos(skpr / (norm1 * norm2));
*
* return ((180 / Math.PI) * alpha);*/
}
private tEdge addEdge(DerivationContext aContext, IPhrase aPhr, IPhrase aParent)
{
tGraph graph = (aContext as BuildGraphContext).BuildingGraph;
string fromName = "unk";
string toName = "unk";
// determine fromName
if (aParent == null)
{
fromName = aContext.Grammar.MainSymbol.CounterName;
graph.ensureExistsNode(fromName, aContext.Grammar.MainSymbol.Text);
}
else
{
NonTerminal parentNt = aParent as NonTerminal;
if (parentNt != null)
{
fromName = parentNt.CounterName;
graph.ensureExistsNode(parentNt.CounterName, parentNt.Text);
}
else
{
fromName = (aContext as BuildGraphContext).GeneratedToName;
Debug.Assert(!string.IsNullOrEmpty(fromName), "Не должно быть");
}
}
// determine toName
NonTerminal nonTerminal = aPhr as NonTerminal;
Terminal terminal = aPhr as Terminal;
if (nonTerminal != null)
{
toName = nonTerminal.CounterName;
string text = nonTerminal.Text;
if ((nonTerminal.CycicKind & CycicKind.SkippedAsSeen) > 0)
{
text += " *";
}
graph.ensureExistsNode(toName, text);
}
else if (terminal != null)
{
string text = string.IsNullOrEmpty(terminal.Text) ? "e" : terminal.Text;
tNode n = graph.addNonUniqueNode(text);
toName = n.Name;
n.CustomAttributes = "term";
}
else
{
toName = graph.addNonUniqueNode(aPhr.ToString()).Name;
//надо запомнить это в контексте
(aContext as BuildGraphContext).GeneratedToName = toName;
}
tEdge e = graph.addEdge(fromName, toName);
if (e == null)
{
Debug.WriteLine("не создалась дуга, потому что нет вершин");
}
return(e);
}
