/// <summary>
/// Merges the with hole.
/// </summary>
public Polygon2D MergeWithHole(Polygon2D actHole, Polygon2DMergeOptions mergeOptions, List <Vector2>?cutPoints)
{
//This algorithm uses the method described in http://www.geometrictools.com/Documentation/TriangulationByEarClipping.pdf
//Find the hole vertex with the highest x value
var holeVertexWithHighestX = new Vector2(float.MinValue, 0f);
var holeVertexIndexWithHighestX = -1;
for (var loopVertex = 0; loopVertex < actHole._vertices.Length; loopVertex++)
{
if (actHole._vertices[loopVertex].X > holeVertexWithHighestX.X)
{
holeVertexWithHighestX = actHole._vertices[loopVertex];
holeVertexIndexWithHighestX = loopVertex;
}
}
cutPoints?.Add(holeVertexWithHighestX);
//Define a ray from the found vertex pointing in x direction
var ray2D = new Ray2D(holeVertexWithHighestX, new Vector2(1f, 0f));
//Find the line on current filling polygon with intersects first with the created ray
Tuple <int, float, Vector2>?foundLine = null;
var actLineIndex = 0;
foreach (var actLine in this.Lines)
{
var actIntersection = actLine.Intersect(ray2D);
if (actIntersection.Item1)
{
var rayToIntersectionPoint = new Ray2D(
ray2D.Origin,
Vector2.Normalize(actIntersection.Item2 - ray2D.Origin));
var lengthToIntersectionPoint = Vector2.Distance(actIntersection.Item2, ray2D.Origin);
if (lengthToIntersectionPoint > 0f &&
rayToIntersectionPoint.EqualsWithTolerance(ray2D))
{
if (foundLine == null)
{
//First found intersection
foundLine = Tuple.Create(actLineIndex, lengthToIntersectionPoint, actIntersection.Item2);
}
else if (lengthToIntersectionPoint < foundLine.Item2)
{
//More intersections found.. take the one with smallest distance to intersection point
foundLine = Tuple.Create(actLineIndex, lengthToIntersectionPoint, actIntersection.Item2);
}
}
}
actLineIndex++;
}
if (cutPoints != null && foundLine != null)
{
cutPoints.Add(foundLine.Item3);
}
// Check for found intersection
// Return a duplicate of this polygon as the result if no intersection found
if (foundLine == null)
{
var newPolygonVertices = new Vector2[_vertices.Length];
Array.Copy(_vertices, newPolygonVertices, _vertices.Length);
return(new Polygon2D(newPolygonVertices));
}
//Now generate result polygon
var resultBuilder = new List <Vector2>(_vertices.Length + actHole._vertices.Length + 2);
for (var loopFillVertex = 0; loopFillVertex < _vertices.Length; loopFillVertex++)
{
//Add current vertex from filling polygon first
resultBuilder.Add(_vertices[loopFillVertex]);
//Do special logic on cut point
if (loopFillVertex == foundLine.Item1)
{
//Cut point.. place here the hole polygon
if (!_vertices[loopFillVertex].Equals(foundLine.Item3))
{
resultBuilder.Add(foundLine.Item3);
}
//Add all vertices from the hole polygon
resultBuilder.Add(actHole._vertices[holeVertexIndexWithHighestX]);
var loopHoleVertex = holeVertexIndexWithHighestX + 1;
while (loopHoleVertex != holeVertexIndexWithHighestX)
{
if (loopHoleVertex >= actHole._vertices.Length)
{
loopHoleVertex = 0;
}
resultBuilder.Add(actHole._vertices[loopHoleVertex]);
loopHoleVertex++;
if (loopHoleVertex >= actHole._vertices.Length)
{
loopHoleVertex = 0;
}
}
//Add cutpoints again to continue with main polygon
if (mergeOptions.MakeMergepointSpaceForTriangulation)
{
resultBuilder.Add(actHole._vertices[holeVertexIndexWithHighestX] + new Vector2(0f, 0.001f));
//Add the cutpoint again
resultBuilder.Add(foundLine.Item3 + new Vector2(0f, 0.001f));
}
else
{
resultBuilder.Add(actHole._vertices[holeVertexIndexWithHighestX]);
//Add the cutpoint again
resultBuilder.Add(foundLine.Item3);
}
//Handle the case in which next vertex would equal current cut point
if (_vertices.Length > loopFillVertex + 1 &&
_vertices[loopFillVertex + 1].Equals(foundLine.Item3))
{
loopFillVertex++;
}
}
}
//Return new generate polygon
return(new Polygon2D(resultBuilder.ToArray()));
}
/// <summary>
/// Merges this polygon with the given one defining a hole. The result is a new polygon.
/// </summary>
public Polygon2D MergeWithHole(Polygon2D actHole, Polygon2DMergeOptions mergeOptions)
{
return(this.MergeWithHole(actHole, mergeOptions, null));
}