public static float PlacePoint(Vector start, Vector end, Vector point)
{
float a = start.y - end.y;
float b = -(start.x - end.x);
float c = -(a * start.x + b * start.y);
return a * point.x + b * point.y + c;
}
public float PlaceOfPoint(Vector point)
{
float a = begin.Y - end.Y;
float b = -(begin.X - end.X);
float c = -(a * begin.X + b * begin.Y);
return a * point.X + b * point.Y + c;
}
public static Vector CrossingPoint(Vector a1, Vector a2, Vector b1, Vector b2)
{
float x = -((a1.x * a2.y - a2.x * a1.y) * (b2.x - b1.x) - (b1.x * b2.y - b2.x * b1.y) * (a2.x - a1.x)) / ((a1.y - a2.y) * (b2.x - b1.x) - (b1.y - b2.y) * (a2.x - a1.x));
if (x == float.NaN)
return null;
float y = ((b1.y - b2.y) * (-x) - (b1.x * b2.y - b2.x * b1.y)) / (b2.x - b1.x);
return new Vector(x, y);
}
public bool ContainPoint(Vector point)
{
float end = (new Vector(points.Last(), points.First())) * (new Vector(points.Last(), point));
for (int i = 0; i < points.Count-1; i++ )
{
float step = (new Vector(points[i], points[i+1])) * (new Vector(points[i], point));
if (end * step < 0)
return false;
}
return true;
}
public static Polygon Intersection(Polygon a, Vector b1, Vector b2)
{
List<Vector> result = new List<Vector>();
a.points.Add(a.points.Last());
for (int i = 0; i < a.points.Count - 1; i++)
{
Vector start = a.points[i];
Vector end = a.points[i + 1];
bool s = Vector.PlacePoint(b1, b2, start) >= 0;
bool e = Vector.PlacePoint(b1, b2, end) >= 0;
if (s)
result.Add(start);
if (s ^ e)
result.Add(Vector.CrossingPoint(start, end, b1, b2));
}
return new Polygon(result);
}
public Segment(Vector begin, Vector end)
{
this.begin = begin;
this.end = end;
}
public Vector(Vector a, Vector b)
{
this.x = b.x - a.x;
this.y = b.y - a.y;
}