public CentralTriangle(Vector <double> a, Vector <double> b)
{
Vectors.Add(a);
Vectors.Add(b);
double normalLength = a.First() * b.Last() - a.Last() * b.First(); //Length of a vector product
if (Math.Abs(normalLength) < double.Epsilon)
{
Sign = Sign.Zero;
}
else if (normalLength > 0)
{
Sign = Sign.Positive;
}
else
{
Sign = Sign.Negative;
}
if (Sign != Sign.Zero)
{
Area = 0.5 * Math.Abs(normalLength);
Vector <double> gravityCenterVector = a.Add(b) / 3;
GravityCenter.X = gravityCenterVector[0];
GravityCenter.Y = gravityCenterVector[1];
StaticMoments = new StaticMoments(GetStaticMoment(Axle.X), GetStaticMoment(Axle.Y));
MomentsOfInertia = new MomentsOfInertia(GetMomentOfInertia(Axle.X), GetMomentOfInertia(Axle.Y));
}
else
{
Area = 0.0;
GravityCenter.X = 0.0;
GravityCenter.Y = 0.0;
StaticMoments = new StaticMoments(0.0, 0.0);
MomentsOfInertia = new MomentsOfInertia(0.0, 0.0);
}
}
public CrossSection(List <Point> points)
{
Vertices = points;
Boundaries = new Boundaries();
StaticMoments = new StaticMoments();
MomentsOfInertia = new MomentsOfInertia();
Boundaries.Left = points[0].X;
Boundaries.Right = points[0].X;
Boundaries.Bottom = points[0].Y;
Boundaries.Top = points[0].Y;
if (points.First() != points.Last())
{
points.Add(points[0]);
}
for (int i = 0; i < points.Count() - 1; i++)
{
Triangles.Add(new CentralTriangle(points[i], points[i + 1]));
Area += ((int)Triangles.Last().Sign) * Triangles.Last().Area;
StaticMoments.SX += ((int)Triangles.Last().Sign) * Triangles.Last().StaticMoments.SX;
StaticMoments.SY += ((int)Triangles.Last().Sign) * Triangles.Last().StaticMoments.SY;
if (points[i].X < Boundaries.Left)
{
Boundaries.Left = points[i].X;
}
if (points[i].X > Boundaries.Right)
{
Boundaries.Right = points[i].X;
}
if (points[i].Y < Boundaries.Bottom)
{
Boundaries.Bottom = points[i].Y;
}
if (points[i].Y > Boundaries.Top)
{
Boundaries.Top = points[i].Y;
}
}
if (Area < 0.0)
{
throw new Exception("Invalid shape definition.");
}
GravityCenter = new Point(StaticMoments.SY / Area, StaticMoments.SX / Area);
Boundaries.Left = Boundaries.Left - GravityCenter.X;
Boundaries.Right = Boundaries.Right - GravityCenter.X;
Boundaries.Bottom = Boundaries.Bottom - GravityCenter.Y;
Boundaries.Top = Boundaries.Top - GravityCenter.Y;
foreach (CentralTriangle triangle in Triangles)
{
MomentsOfInertia.IX += ((int)triangle.Sign) * (triangle.MomentsOfInertia.IX + triangle.Area * Math.Pow(GravityCenter.Y - triangle.GravityCenter.Y, 2) - triangle.Area * Math.Pow(triangle.GravityCenter.Y, 2));
MomentsOfInertia.IY += ((int)triangle.Sign) * (triangle.MomentsOfInertia.IY + triangle.Area * Math.Pow(GravityCenter.X - triangle.GravityCenter.X, 2) - triangle.Area * Math.Pow(triangle.GravityCenter.X, 2));
}
}