static Vector3 GetVertexOfOrbitEllipse(double a, double ecc, double nu, double[,] T)
{
double E = OrbitUtils.TrueAnom2EccentricAnom(nu, ecc);
double rx = a * (Math.Cos(E) - ecc);
double ry = a * Math.Sqrt(1 - ecc * ecc) * Math.Sin(E);
return((Vector3)OrbitUtils.ApplyTransform(rx, ry, T));
}
/// <summary>
/// Updates the position and velocity of the body in its orbit based on
/// the current anomaly. Reference plane is the ecliptic plane (J2000).
/// </summary>
void UpdatePositionAndVelocity()
{
// Heliocentric coordinates in its orbital plane r'.
double rx = a * (Math.Cos(E) - ecc);
double ry = a * Math.Sqrt(1 - ecc * ecc) * Math.Sin(E);
// Heliocentric velocity in its orbital plane v'.
double cosE = Math.Cos(E);
double r = a * (1 - ecc * cosE);
double k = Math.Sqrt(mu * a) / r;
double vx = k * -Math.Sin(E);
double vy = k * Math.Sqrt(1 - ecc * ecc) * cosE;
double[,] T = OrbitUtils.GetTransformToEcliptic(i, Om, w);
pos = OrbitUtils.ApplyTransform(rx, ry, T);
vel = OrbitUtils.ApplyTransform(vx, vy, T);
}