private ICoordinate getCircleCenter(ICoordinate p1, ICoordinate p2, ICoordinate p3)
{
if (p1.ExactEquals(p2) || p1.ExactEquals(p3) || p2.ExactEquals(p3))
{
return(null);
}
// get rid of the vertical lines
if (p1.X == p2.X)
{
ICoordinate temp = p1;
p1 = p3;
p3 = temp;
}
if (p2.X == p3.X)
{
ICoordinate temp = p2;
p2 = p1;
p1 = temp;
}
double ma = (p2.Y - p1.Y) / (p2.X - p1.X);
double mb = (p3.Y - p2.Y) / (p3.X - p2.X);
// collinear lines, circles do not
if (mb == ma || (double.IsInfinity(ma) && double.IsInfinity(mb)))
{
return(null);
}
//coordinates of the center of the circle
double x = 0.5 * (ma * mb * (p1.Y - p3.Y) + mb * (p1.X + p2.X) - ma * (p2.X + p3.X)) / (mb - ma);
double y = double.NaN;
if (ma != 0 && !double.IsInfinity(ma))
{
y = -1 / ma * (x - 0.5 * (p1.X + p2.X)) + 0.5 * (p1.Y + p2.Y);
}
else
{
y = -1 / mb * (x - 0.5 * (p2.X + p3.X)) + 0.5 * (p2.Y + p3.Y);
}
return(PlanimetryEnvironment.NewCoordinate(x, y));
}
private bool checkWeightedVertex(Polyline polyline, KDTree vertexIndex, SDMinVertex currentVertex, KDTree crossPointIndex)
{
// probably not an internal vertex
if (currentVertex.Previous == null || currentVertex.Next == null)
{
return(true);
}
// top with infinite weight ("do not remove")
if (double.IsPositiveInfinity(currentVertex.Weight))
{
return(true);
}
SDMinVertex previous = currentVertex.Previous;
SDMinVertex next = currentVertex.Next;
// One of the segments formed by the vertex in question may be one of the intersection points.
// If so, you can not remove the top, as point of self-intersection, it may be removed.
Segment s1 = new Segment(pointOfWeightedVertex(polyline, currentVertex),
pointOfWeightedVertex(polyline, previous));
Segment s2 = new Segment(pointOfWeightedVertex(polyline, currentVertex),
pointOfWeightedVertex(polyline, next));
List <SDMinCrossPoint> crossPoints = new List <SDMinCrossPoint>();
crossPointIndex.QueryObjectsInRectangle(s1.GetBoundingRectangle(), crossPoints);
crossPointIndex.QueryObjectsInRectangle(s2.GetBoundingRectangle(), crossPoints);
foreach (SDMinCrossPoint point in crossPoints)
{
if (PlanimetryAlgorithms.LiesOnSegment(point.Point, s1))
{
currentVertex.IsCrossSegmentVertex = true;
currentVertex.Previous.IsCrossSegmentVertex = true;
return(false);
}
if (PlanimetryAlgorithms.LiesOnSegment(point.Point, s2))
{
currentVertex.IsCrossSegmentVertex = true;
currentVertex.Next.IsCrossSegmentVertex = true;
return(false);
}
}
//One of the polyline vertices can belong to a triangle,
//the apex of which is considered the top. In this case,
//the top can not be deleted because will be a new point of self-intersection.
Polygon triangle = new Polygon(new ICoordinate[] { pointOfWeightedVertex(polyline, previous),
pointOfWeightedVertex(polyline, currentVertex),
pointOfWeightedVertex(polyline, next) });
List <SDMinVertex> vertices = new List <SDMinVertex>();
vertexIndex.QueryObjectsInRectangle <SDMinVertex>(triangle.GetBoundingRectangle(), vertices);
foreach (SDMinVertex vertex in vertices)
{
ICoordinate p = pointOfWeightedVertex(polyline, vertex);
//point should not be the top of the triangle
if (p.ExactEquals(triangle.Contours[0].Vertices[0]) ||
p.ExactEquals(triangle.Contours[0].Vertices[1]) ||
p.ExactEquals(triangle.Contours[0].Vertices[2]))
{
continue;
}
if (triangle.ContainsPoint(p))
{
return(false);
}
}
return(true);
}