private bool CanRemoveEdge(int index)
{
var edge = this.PolygonEdges[index];
// (Assumes CCW list in polygons)
// (Assumes the edge is CCW along polygon A)
// In order to be able to remove an edge and (eventually) combine the polygons together two corners where the polygons match be less than 180 degress
// CornerA: (P1 - A.prev) x (B.next - P1)
{
int indexA = edge.PolygonA.IndexOf(edge.EdgePoint1);
int indexPrevA = edge.PolygonA.PreviousIndex(indexA);
int indexB = edge.PolygonB.IndexOf(edge.EdgePoint1);
int indexNextB = edge.PolygonB.NextIndex(indexB);
Poly2Tri.Point2D prevA = edge.PolygonA[indexPrevA];
Poly2Tri.Point2D nextB = edge.PolygonB[indexNextB];
Poly2Tri.Point2D line1 = edge.EdgePoint1 - prevA;
Poly2Tri.Point2D line2 = nextB - edge.EdgePoint1;
double cross = Poly2Tri.Point2D.Cross(line1, line2);
if (cross < 0)
{
return(false);
}
}
// CornerB: (A.next - P2) x (P2 - B.prev)
{
int indexA = edge.PolygonA.IndexOf(edge.EdgePoint2);
int indexNextA = edge.PolygonA.NextIndex(indexA);
int indexB = edge.PolygonB.IndexOf(edge.EdgePoint2);
int indexPrevB = edge.PolygonB.PreviousIndex(indexB);
Poly2Tri.Point2D nextA = edge.PolygonA[indexNextA];
Poly2Tri.Point2D prevB = edge.PolygonB[indexPrevB];
Poly2Tri.Point2D line1 = nextA - edge.EdgePoint2;
Poly2Tri.Point2D line2 = edge.EdgePoint2 - prevB;
double cross = Poly2Tri.Point2D.Cross(line1, line2);
if (cross > 0)
{
return(false);
}
}
return(true);
}
public static Vector2 poly2triToUnity(Poly2Tri.Point2D pt)
{
return(new Vector2(pt.Xf, pt.Yf));
}
public static ClipperLib.IntPoint poly2triToClipper(Poly2Tri.Point2D pt)
{
return(new ClipperLib.IntPoint((long)(pt.X * scalar), (long)(pt.Y * scalar)));
}
private void CombinePolygonsAlongEdge(int index)
{
// We are going to combine all the points from polygon B into polygon A
var edge = this.PolygonEdges[index];
// Gather a list of all the points from polygon B to be added
// This is all the points from polygon B except for the shared edge
List <Poly2Tri.Point2D> pointsToAdd = new List <Poly2Tri.Point2D>();
{
int edgeStartOnBIndex = edge.PolygonB.IndexOf(edge.EdgePoint1);
int edgeStopOnBIndex = edge.PolygonB.IndexOf(edge.EdgePoint2);
int indexToAdd = edge.PolygonB.NextIndex(edgeStartOnBIndex);
while (indexToAdd != edgeStopOnBIndex)
{
Poly2Tri.Point2D point = edge.PolygonB[indexToAdd];
pointsToAdd.Add(point);
indexToAdd = edge.PolygonB.NextIndex(indexToAdd);
}
}
// Insert the points to add between the edge points on polygon A
List <Poly2Tri.Point2D> newPolygonAPoints = edge.PolygonA.ToList();
{
int edgeStartOnAIndex = edge.PolygonA.IndexOf(edge.EdgePoint1);
int nextIndexA = edge.PolygonA.NextIndex(edgeStartOnAIndex);
newPolygonAPoints.InsertRange(nextIndexA, pointsToAdd);
}
// Create a new polygon A
Poly2Tri.Point2DList newPolygonA = new Poly2Tri.Point2DList(newPolygonAPoints);
this.Polygons.Add(newPolygonA);
// Any furter edges that had PolygonA or PolygonB in it must be updated
for (int i = index + 1; i < this.PolygonEdges.Count; ++i)
{
var furtherEdge = this.PolygonEdges[i];
if (furtherEdge.PolygonA == edge.PolygonA)
{
furtherEdge.PolygonA = newPolygonA;
}
else if (furtherEdge.PolygonA == edge.PolygonB)
{
furtherEdge.PolygonA = newPolygonA;
}
if (furtherEdge.PolygonB == edge.PolygonA)
{
furtherEdge.PolygonB = newPolygonA;
}
else if (furtherEdge.PolygonB == edge.PolygonB)
{
furtherEdge.PolygonB = newPolygonA;
}
}
// Old PolygonA and PolygonB are removed from the list of polygons
this.Polygons.Remove(edge.PolygonA);
this.Polygons.Remove(edge.PolygonB);
}
