/// <summary>
/// Traces a massive body orbit by re-centering the world around the parent.
/// </summary>
public static OrbitTrace TraceMassiveBody(MassiveBodyBase body)
{
IMassiveBody parent = body.GravitationalParent;
DVector2 initialPosition = body.Position - parent.Position;
var proxyParent = new MassiveBodyProxy(DVector2.Zero, DVector2.Zero, parent);
var proxySatellite = new MassiveBodyProxy(initialPosition, body.Velocity - parent.Velocity, body);
double orbitalTerminationRadius;
double altitude = body.GetRelativeAltitude();
double orbitalDt = GetOrbitalDt(initialPosition, proxySatellite.Velocity, out orbitalTerminationRadius);
var trace = new OrbitTrace(body.Position, altitude);
for (int i = 0; i < 300; i++)
{
proxySatellite.ResetAccelerations();
proxySatellite.ResolveGravitation(proxyParent);
proxySatellite.Update(orbitalDt);
altitude = proxyParent.GetRelativeHeight(proxySatellite.Position);
// Check expensive termination conditions after half of the iterations
if (i > 150)
{
DVector2 offsetVector = proxySatellite.Position - initialPosition;
double distanceFromStart = offsetVector.Length();
// Terminate and add the end point
if (distanceFromStart < orbitalTerminationRadius)
{
trace.AddPoint(proxySatellite.Position + parent.Position, altitude);
break;
}
}
trace.AddPoint(proxySatellite.Position + parent.Position, altitude);
}
return(trace);
}
/// <summary>
/// Traces a massive body orbit by re-centering the world around the parent.
/// </summary>
public static void TraceMassiveBody(MassiveBodyBase body, OrbitTrace trace)
{
IMassiveBody parent = body.GravitationalParent;
DVector2 initialPosition = body.Position - parent.Position;
var proxyParent = new MassiveBodyProxy(DVector2.Zero, DVector2.Zero, parent);
var proxySatellite = new MassiveBodyProxy(initialPosition, body.Velocity - parent.Velocity, body);
double orbitalDt = GetOrbitalDt(initialPosition.Length(), parent.Mass, proxySatellite.Velocity.Length());
trace.Reset(body.Position);
// Assumes that the parent is (0,0) which will be true in this case
double previousAngle = proxySatellite.Position.Angle();
double totalAngularDisplacement = 0;
// Max of 1000 steps, in practice it's 150-200
for (int i = 0; i < 1000; i++)
{
proxySatellite.ResetAccelerations();
proxySatellite.ResolveGravitation(proxyParent);
proxySatellite.Update(orbitalDt);
double currentAngle = proxySatellite.Position.Angle();
totalAngularDisplacement += DeltaAngle(currentAngle, previousAngle);
// Made a full orbit
if (totalAngularDisplacement > AngularCutoff)
{
break;
}
previousAngle = currentAngle;
double altitude = proxyParent.GetRelativeHeight(proxySatellite.Position);
trace.AddPoint(proxySatellite.Position + parent.Position, altitude);
}
}