/// <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);
}
/// <summary>
/// Gets the points on orbit ellipse.
/// </summary>
/// <param name="vertices">Reference array storing the vertices of the ellipse.</param>
/// <param name="resolution">Number of vertices to draw ellipse.</param>
public void GetEllipseFromTrueAnom(ref Vector3[] vertices, int resolution)
{
if (resolution < 2)
{
vertices = new Vector3[0];
return;
}
//if (ecc < 1 && ecc >= 0)
if (vertices == null || vertices.Length != resolution)
{
vertices = new Vector3[resolution];
}
// Resolution as the angular distance (nu) between each vertex.
double nuResolution = OrbitUtils.TwoPI / resolution;
double[,] T = OrbitUtils.GetTransformToEcliptic(i, Om, w);
for (int i = 0; i < resolution; i++)
{
vertices[i] = GetVertexOfOrbitEllipse(a, ecc, i * nuResolution, T);
}
}