static bool checkPointToSegment(Vertex sA, Vertex sB, Vertex point)
{
if ((sA.Position.Y < point.Position.Y && sB.Position.Y >= point.Position.Y) ||
(sB.Position.Y < point.Position.Y && sA.Position.Y >= point.Position.Y))
{
float x =
sA.Position.X +
(point.Position.Y - sA.Position.Y) /
(sB.Position.Y - sA.Position.Y) *
(sB.Position.X - sA.Position.X);
if (x < point.Position.X)
return true;
}
return false;
}
public bool ContainsPoint(Vertex point)
{
//return true if the point to test is one of the vertices
if (point.Equals(A) || point.Equals(B) || point.Equals(C))
return true;
bool oddNodes = false;
if (checkPointToSegment(C, A, point))
oddNodes = !oddNodes;
if (checkPointToSegment(A, B, point))
oddNodes = !oddNodes;
if (checkPointToSegment(B, C, point))
oddNodes = !oddNodes;
return oddNodes;
}
public LineSegment(Vertex a, Vertex b)
{
A = a;
B = b;
}
private static void ValidateAdjacentVertex(Vertex vertex)
{
Log("Validating: {0}...", vertex);
if (reflexVertices.Contains(vertex))
{
if (IsConvex(vertex))
{
reflexVertices.Remove(vertex);
convexVertices.Add(vertex);
Log("Vertex: {0} now convex", vertex);
}
else
{
Log("Vertex: {0} still reflex", vertex);
}
}
if (convexVertices.Contains(vertex))
{
bool wasEar = earVertices.Contains(vertex);
bool isEar = IsEar(vertex);
if (wasEar && !isEar)
{
earVertices.Remove(vertex);
Log("Vertex: {0} no longer ear", vertex);
}
else if (!wasEar && isEar)
{
earVertices.AddFirst(vertex);
Log("Vertex: {0} now ear", vertex);
}
else
{
Log("Vertex: {0} still ear", vertex);
}
}
}
private static bool IsReflex(Vertex c)
{
return !IsConvex(c);
}
private static bool IsEar(Vertex c)
{
Vertex p = polygonVertices[polygonVertices.IndexOf(c) - 1].Value;
Vertex n = polygonVertices[polygonVertices.IndexOf(c) + 1].Value;
Log("Testing vertex {0} as ear with triangle {1}, {0}, {2}...", c, p, n);
foreach (Vertex t in reflexVertices)
{
if (t.Equals(p) || t.Equals(c) || t.Equals(n))
continue;
if (Triangle.ContainsPoint(p, c, n, t))
{
Log("\tTriangle contains vertex {0}...", t);
return false;
}
}
return true;
}
private static bool IsConvex(Vertex c)
{
Vertex p = polygonVertices[polygonVertices.IndexOf(c) - 1].Value;
Vertex n = polygonVertices[polygonVertices.IndexOf(c) + 1].Value;
Vector2 d1 = Vector2.Normalize(c.Position - p.Position);
Vector2 d2 = Vector2.Normalize(n.Position - c.Position);
Vector2 n2 = new Vector2(-d2.Y, d2.X);
return (Vector2.Dot(d1, n2) <= 0f);
}
public static bool ContainsPoint(Vertex a, Vertex b, Vertex c, Vertex point)
{
return new Triangle(a, b, c).ContainsPoint(point);
}
public Triangle(Vertex a, Vertex b, Vertex c)
{
A = a;
B = b;
C = c;
}
public bool Equals(Vertex obj)
{
return obj.Position.Equals(Position) && obj.Index == Index;
}
public bool Equals(Vertex obj)
{
return(obj.Position.Equals(Position) && obj.Index == Index);
}