/// <summary>
/// Orders the vertices of the polygon in the x-direction.
/// </summary>
/// <param name="polygon">The polygon.</param>
/// <returns>Vertex2D[].</returns>
public static Vertex2D[] SortVerticesByYValue(this IEnumerable <Polygon> polygons)
{
var yStrands = new List <Vertex2D[]>();
var numVertices = 0;
foreach (var polygon in polygons)
{
numVertices += polygon.Vertices.Count;
foreach (var monoBox in polygon.PartitionIntoMonotoneBoxes(MonotonicityChange.Y))
{
var newStrand = new List <Vertex2D>();
var vertex = monoBox.Vertex1;
while (vertex != monoBox.Vertex2)
{
newStrand.Add(vertex);
vertex = vertex.StartLine.ToPoint;
}
if (!monoBox.YInPositiveMonotonicity)
{
newStrand.Reverse();
}
yStrands.Add(newStrand.ToArray());
}
}
var sortedVertices = new Vertex2D[numVertices];
var i = 0;
foreach (var vertex in CombineYSortedVerticesIntoOneCollection(yStrands))
{
sortedVertices[i++] = vertex;
}
return(sortedVertices);
}
/// <summary>
/// Orders the vertices of the polygon in the x-direction.
/// </summary>
/// <param name="polygon">The polygon.</param>
/// <returns>Vertex2D[].</returns>
internal static Vertex2D[] SortVerticesByXValue(this Polygon polygon)
{
return(polygon.Vertices.OrderBy(v => v, new VertexSortedByXFirst()).ToArray());
var xStrands = new List <Vertex2D[]>();
foreach (var monoBox in polygon.PartitionIntoMonotoneBoxes(MonotonicityChange.X))
{
var newStrand = new List <Vertex2D>();
var vertex = monoBox.Vertex1;
while (vertex != monoBox.Vertex2)
{
newStrand.Add(vertex);
vertex = vertex.StartLine.ToPoint;
}
if (!monoBox.XInPositiveMonotonicity)
{
newStrand.Reverse();
}
xStrands.Add(newStrand.ToArray());
}
var numVertices = polygon.Vertices.Count;
var sortedVertices = new Vertex2D[numVertices];
var i = 0;
foreach (var vertex in CombineXSortedVerticesIntoOneCollection(xStrands))
{
sortedVertices[i++] = vertex;
}
return(sortedVertices);
}
/// <summary>
/// Gets the other point that makes up this line.
/// </summary>
/// <param name="point"></param>
/// <returns></returns>
public Vertex2D OtherPoint(Vertex2D point)
{
if (point == FromPoint)
{
return(ToPoint);
}
return(point == ToPoint ? FromPoint : null);
}
/// <summary>
/// Sets to and from nodes as well as slope and intercept of line.
/// </summary>
/// <param name="fromNode">From node.</param>
/// <param name="toNode">To node.</param>
internal PolygonEdge(Vertex2D fromNode, Vertex2D toNode)
{
FromPoint = fromNode;
ToPoint = toNode;
XMax = (FromPoint.X > ToPoint.X) ? FromPoint.X : ToPoint.X;
XMin = (FromPoint.X < ToPoint.X) ? FromPoint.X : ToPoint.X;
YMax = (FromPoint.Y > ToPoint.Y) ? FromPoint.Y : ToPoint.Y;
YMin = (FromPoint.Y < ToPoint.Y) ? FromPoint.Y : ToPoint.Y;
}
/// <summary>
/// Makes the vertices.
/// </summary>
private void MakeVertices()
{
foreach (var polygon in AllPolygons)
{
var numPoints = polygon._path.Count;
var pointsArray = new Vertex2D[numPoints];
for (int i = 0; i < numPoints; i++)
{
pointsArray[i] = new Vertex2D(polygon._path[i], i, Index);
}
polygon._vertices = pointsArray.ToList();
}
}
public MonotoneBox(Vertex2D vertex1, Vertex2D vertex2, MonotonicityChange lowMonoChange,
MonotonicityChange hiMonoChange, bool xInPositiveMonotonicity, bool yInPositiveMonotonicity) : this()
{
this.Vertex1 = vertex1;
this.Vertex2 = vertex2;
this.LowChange = lowMonoChange;
this.HiChange = hiMonoChange;
XInPositiveMonotonicity = xInPositiveMonotonicity;
YInPositiveMonotonicity = yInPositiveMonotonicity;
Left = Math.Min(vertex1.X, vertex2.X);
Right = Math.Max(vertex1.X, vertex2.X);
Bottom = Math.Min(vertex1.Y, vertex2.Y);
Top = Math.Max(vertex1.Y, vertex2.Y);
}
public static IEnumerable <Polygon> CreateXMonotonePolygons(this Polygon polygon)
{
polygon.MakePolygonEdgesIfNonExistent();
var connections = FindInternalDiagonalsForMonotone(polygon);
foreach (var edge in polygon.Edges)
{
AddNewConnection(connections, edge.FromPoint, edge.ToPoint);
}
foreach (var edge in polygon.InnerPolygons.SelectMany(p => p.Edges))
{
AddNewConnection(connections, edge.FromPoint, edge.ToPoint);
}
while (connections.Any())
{
var startingConnectionKVP = connections.First();
var start = startingConnectionKVP.Key;
var newVertices = new List <Vertex2D> {
start
};
var current = start;
var nextConnections = startingConnectionKVP.Value;
Vertex2D next = nextConnections[0];
while (next != start)
{
newVertices.Add(next);
RemoveConnection(connections, current, next);
current = next;
nextConnections = connections[current];
if (nextConnections.Count == 1)
{
next = nextConnections[0];
}
else
{
next = ChooseTightestLeftTurn(nextConnections, current,
current.Coordinates - newVertices[^ 2].Coordinates);
/// <summary>Gets the monotonicity change.</summary>
/// <param name="vertex">The vertex.</param>
/// <param name="tolerance">The tolerance.</param>
/// <returns>MonotonicityChange.</returns>
/// <exception cref="ArgumentException">
/// vertex does not conenct to polygon edges. Be sure to invoke" +
/// " MakePolygonEdgesIfNonExistent on parent polygon before this calling this method. - vertex
/// </exception>
public static MonotonicityChange GetMonotonicityChange(this Vertex2D vertex, double tolerance)
{
if (vertex.EndLine == null)
{
throw new ArgumentException("vertex does not connect to polygon edges. Be sure to invoke" +
" MakePolygonEdgesIfNonExistent on parent polygon before this calling this method.", nameof(vertex));
}
var xPrev = vertex.EndLine.Vector.X;
var yPrev = vertex.EndLine.Vector.Y;
if (xPrev.IsNegligible() && yPrev.IsNegligible())
{
return(MonotonicityChange.SameAsPrevious);
}
double xNext, yNext;
var neighborVertex = vertex.StartLine.ToPoint;
do
{
xNext = neighborVertex.EndLine.Vector.X;
yNext = neighborVertex.EndLine.Vector.Y;
neighborVertex = neighborVertex.StartLine.ToPoint;
}while (xNext.IsNegligible(tolerance) && yNext.IsNegligible(tolerance));
//at this point one or both of the x&y deltas are non-negligible.
/**** I wish this were enough (the next 6 lines) but it leads to problems
* var xProduct = xNext * xPrev;
* var yProduct = yNext * yPrev;
* if (xProduct > 0 && yProduct > 0) return MonotonicityChange.Neither;
* if (xProduct < 0 && yProduct < 0) return MonotonicityChange.Both;
* if (xProduct > 0) return MonotonicityChange.Y;
* return MonotonicityChange.X;
****/
// first check the cases where all four numbers are not negligible
var xChangesDir = (xPrev.IsNegativeNonNegligible(tolerance) && xNext.IsPositiveNonNegligible(tolerance)) ||
(xPrev.IsPositiveNonNegligible(tolerance) && xNext.IsNegativeNonNegligible(tolerance));
var yChangesDir = (yPrev.IsNegativeNonNegligible(tolerance) && yNext.IsPositiveNonNegligible(tolerance)) ||
(yPrev.IsPositiveNonNegligible(tolerance) && yNext.IsNegativeNonNegligible(tolerance));
if (xChangesDir && yChangesDir)
{
return(MonotonicityChange.Both);
}
var xSameDir = (xPrev.IsNegativeNonNegligible(tolerance) && xNext.IsNegativeNonNegligible(tolerance)) ||
(xPrev.IsPositiveNonNegligible(tolerance) && xNext.IsPositiveNonNegligible(tolerance));
if (yChangesDir && xSameDir)
{
return(MonotonicityChange.Y);
}
var ySameDir = (yPrev.IsNegativeNonNegligible(tolerance) && yNext.IsNegativeNonNegligible(tolerance)) ||
(yPrev.IsPositiveNonNegligible(tolerance) && yNext.IsPositiveNonNegligible(tolerance));
if (xChangesDir && ySameDir)
{
return(MonotonicityChange.X);
}
if (xSameDir && ySameDir)
{
return(MonotonicityChange.Neither);
}
// if at this point then one or more values in the vectors is zero/negligible since the above booleans were
// defined with this restriction
if (xPrev.IsNegligible(tolerance) && xNext.IsNegligible(tolerance)) // then line is vertical
{
return((Math.Sign(yPrev) == Math.Sign(yNext)) ? MonotonicityChange.Neither : MonotonicityChange.Y);
}
// eww, the latter in that return is problematic at it would be a knife edge. but that's not this functions job to police
if (yPrev.IsNegligible(tolerance) && yNext.IsNegligible(tolerance)) // then line is horizontal
{
return((Math.Sign(xPrev) == Math.Sign(xNext)) ? MonotonicityChange.Neither : MonotonicityChange.X);
}
// at this point, we've checked that 1) no vector is zero, 2) all are nonnegligible,
// 3) either both x's or both y's are negligible.
neighborVertex = vertex;
if (xPrev.IsNegligible(tolerance)) //we know that yPrev != 0 (given first condition) and we know xNext != 0 (given
// the condition before the last). it's possible that yNext is zero, but it doesn't affect the approach
{
do
{
neighborVertex = neighborVertex.EndLine.FromPoint;
xPrev = neighborVertex.EndLine.Vector.X;
} while (xPrev.IsNegligible(tolerance));
xChangesDir = Math.Sign(xPrev) != Math.Sign(xNext);
}
else if (xNext.IsNegligible(tolerance))
{
do
{
neighborVertex = neighborVertex.StartLine.ToPoint;
xNext = neighborVertex.EndLine.Vector.X;
} while (xNext.IsNegligible(tolerance));
xChangesDir = Math.Sign(xPrev) != Math.Sign(xNext);
}
neighborVertex = vertex;
if (yPrev.IsNegligible(tolerance))
{
do
{
neighborVertex = neighborVertex.EndLine.FromPoint;
yPrev = neighborVertex.EndLine.Vector.Y;
} while (yPrev.IsNegligible(tolerance));
yChangesDir = (Math.Sign(yPrev) != Math.Sign(yNext));
}
else if (yNext.IsNegligible(tolerance))
{
do
{
neighborVertex = neighborVertex.StartLine.ToPoint;
yNext = neighborVertex.EndLine.Vector.Y;
} while (yNext.IsNegligible(tolerance));
yChangesDir = Math.Sign(yPrev) != Math.Sign(yNext);
}
if (xChangesDir && yChangesDir)
{
return(MonotonicityChange.Both);
}
if (xChangesDir)
{
return(MonotonicityChange.X);
}
if (yChangesDir)
{
return(MonotonicityChange.Y);
}
return(MonotonicityChange.Neither);
}
/// <summary>
/// Partitions the into monotone boxes.
/// </summary>
/// <param name="polygon">The polygon.</param>
/// <param name="divideAt">The divide at.</param>
/// <returns>System.Collections.Generic.IEnumerable<TVGL.TwoDimensional.MonotoneBox>.</returns>
/// <exception cref="MonotoneBox">polygon.Vertices[0], polygon.Vertices[1], MonotonicityChange.Both, MonotonicityChange.Both, true, true</exception>
public static IEnumerable <MonotoneBox> PartitionIntoMonotoneBoxes(this Polygon polygon, MonotonicityChange divideAt = MonotonicityChange.Both)
{
polygon.MakePolygonEdgesIfNonExistent();
var numPoints = polygon.Vertices.Count;
if (numPoints <= 1)
{
yield return
(new MonotoneBox(polygon.Vertices[0], polygon.Vertices[0], MonotonicityChange.Both,
MonotonicityChange.Both, true, true));
yield break;
}
if (numPoints <= 2)
{
yield return
(new MonotoneBox(polygon.Vertices[0], polygon.Vertices[1], MonotonicityChange.Both,
MonotonicityChange.Both, true, true));
yield break;
}
var initBoxIndex = -1;
var initBoxMonoChange = MonotonicityChange.Neither;
Vertex2D beginBoxVertex = null;
var beginBoxMonoChange = MonotonicityChange.Neither;
var tolerance = polygon.GetToleranceForPolygon();
var i = 0;
while (i % numPoints != initBoxIndex)
{
var vertex = polygon.Vertices[i % numPoints];
var monoChange = GetMonotonicityChange(vertex, tolerance);
if (monoChange == MonotonicityChange.SameAsPrevious || monoChange == MonotonicityChange.Neither)
{
continue;
}
if (monoChange == MonotonicityChange.Both ||
(monoChange == MonotonicityChange.X && (divideAt == MonotonicityChange.X || divideAt == MonotonicityChange.Both)) ||
(monoChange == MonotonicityChange.Y && (divideAt == MonotonicityChange.Y || divideAt == MonotonicityChange.Both)))
{
if (initBoxIndex < 0)
{
initBoxIndex = i;
beginBoxVertex = vertex;
initBoxMonoChange = beginBoxMonoChange = monoChange;
}
else
{
yield return(new MonotoneBox(beginBoxVertex, vertex, beginBoxMonoChange, monoChange,
vertex.X >= beginBoxVertex.X, vertex.Y >= beginBoxVertex.Y));
beginBoxVertex = vertex;
beginBoxMonoChange = monoChange;
}
}
i++;
}
var lastVertex = polygon.Vertices[initBoxIndex];
yield return(new MonotoneBox(beginBoxVertex, lastVertex,
beginBoxMonoChange, initBoxMonoChange,
lastVertex.X - beginBoxVertex.X >= 0,
lastVertex.Y - beginBoxVertex.Y >= 0));
}