/// <summary>
/// Return ratio of perturbation force from third body relative to attraction force of mainAttractor
/// </summary>
/// <param name="targetBody"></param>
/// <param name="mainAttractor"></param>
/// <param name="perturbatingAttractor"></param>
public static double RelativePerturbationRatio(CelestialBody targetBody, CelestialBody mainAttractor, CelestialBody perturbatingAttractor)
{
double mainAcceleration = CelestialBodyUtils.AccelerationByAttractionForce(
targetBody.position,
mainAttractor.position,
mainAttractor.MG).magnitude;
double perturbAcceleration = CelestialBodyUtils.AccelerationByAttractionForce(
targetBody.position,
perturbatingAttractor.position,
perturbatingAttractor.MG).magnitude;
return(perturbAcceleration / mainAcceleration);
}
/// <summary>
/// Calculate and apply n-body gravitational acceleration to target body, using algorythm Runge-Kutta.
/// In result body will change it's velocity according to global gravity.
/// </summary>
/// <param name="body">Target body.</param>
/// <param name="dt">Delta time.</param>
/// <param name="minRange">Minimal attraction range for attractors.</param>
/// <param name="maxRange">Maximal attraction range for attractors.</param>
/// <param name="allAttractors">List of all attractors on scene.</param>
public static void CalcAccelerationRungeKuttaForBody(CelestialBody body, double dt, double minRange, double maxRange, List <CelestialBody> allAttractors)
{
Vector3d result = Vector3d.zero;
body._position += body.Velocity * (dt / 2d);
for (int i = 0; i < allAttractors.Count; i++)
{
if (allAttractors[i] == body)
{
continue;
}
var t1 = CelestialBodyUtils.AccelerationByAttractionForce(
body._position,
allAttractors[i].Position,
allAttractors[i].MG,
minRange,
Mathd.Min(maxRange, allAttractors[i].MaxAttractionRange)
) * dt;
var t2 = CelestialBodyUtils.AccelerationByAttractionForce(
body._position + t1 * 0.5d,
allAttractors[i].Position,
allAttractors[i].MG,
minRange,
Mathd.Min(maxRange, allAttractors[i].MaxAttractionRange)
) * dt;
var t3 = CelestialBodyUtils.AccelerationByAttractionForce(
body._position + t2 * 0.5d,
allAttractors[i].Position,
allAttractors[i].MG,
minRange,
Mathd.Min(maxRange, allAttractors[i].MaxAttractionRange)
) * dt;
var t4 = CelestialBodyUtils.AccelerationByAttractionForce(
body._position + t3,
allAttractors[i].Position,
allAttractors[i].MG,
minRange,
Mathd.Min(maxRange, allAttractors[i].MaxAttractionRange)
) * dt;
result += new Vector3d(
(t1.x + t2.x * 2d + t3.x * 2d + t4.x) / 6d,
(t1.y + t2.y * 2d + t3.y * 2d + t4.y) / 6d,
(t1.z + t2.z * 2d + t3.z * 2d + t4.z) / 6d);
}
if (!result.isZero)
{
body.Velocity += result;
}
}
public void CalcAccelerationRungeKuttaForBody(CelestialBody body, double dt)
{
Vector3d result = Vector3d.zero;
body._position += body.velocity * (dt / 2d);
for (int i = 0; i < attractorsCache.Count; i++)
{
if (attractorsCache[i] == body)
{
continue;
}
var t1 = CelestialBodyUtils.AccelerationByAttractionForce(
body._position,
attractorsCache[i].position,
attractorsCache[i].MG,
minAttractionRange,
Mathd.Min(maxAttractionRange, attractorsCache[i].maxAttractionRange)
) * dt;
var t2 = CelestialBodyUtils.AccelerationByAttractionForce(
body._position + t1 * 0.5d,
attractorsCache[i].position,
attractorsCache[i].MG,
minAttractionRange,
Mathd.Min(maxAttractionRange, attractorsCache[i].maxAttractionRange)
) * dt;
var t3 = CelestialBodyUtils.AccelerationByAttractionForce(
body._position + t2 * 0.5d,
attractorsCache[i].position,
attractorsCache[i].MG,
minAttractionRange,
Mathd.Min(maxAttractionRange, attractorsCache[i].maxAttractionRange)
) * dt;
var t4 = CelestialBodyUtils.AccelerationByAttractionForce(
body._position + t3,
attractorsCache[i].position,
attractorsCache[i].MG,
minAttractionRange,
Mathd.Min(maxAttractionRange, attractorsCache[i].maxAttractionRange)
) * dt;
result += new Vector3d(
(t1.x + t2.x * 2d + t3.x * 2d + t4.x) / 6d,
(t1.y + t2.y * 2d + t3.y * 2d + t4.y) / 6d,
(t1.z + t2.z * 2d + t3.z * 2d + t4.z) / 6d);
}
body.velocity += result;
}
/// <summary>
/// Calculate n-body gravitational acceleration at specified world point, using Euler algorythm.
/// </summary>
/// <param name="pos">World position.</param>
/// <param name="minRange">Minimal attraction range for attractors.</param>
/// <param name="maxRange">Maximal attraction range for attractors.</param>
/// <param name="allAttractors">List of all attractors on scene.</param>
/// <returns>Sum of accelerations vectors at position.</returns>
public static Vector3d CalcAccelerationEulerInPoint(Vector3d pos, double minRange, double maxRange, List <CelestialBody> allAttractors)
{
Vector3d result = new Vector3d();
for (int i = 0; i < allAttractors.Count; i++)
{
if (allAttractors[i].Position == pos)
{
continue;
}
result += CelestialBodyUtils.AccelerationByAttractionForce(
pos,
allAttractors[i].Position,
allAttractors[i].MG,
minRange,
Mathd.Min(maxRange, allAttractors[i].MaxAttractionRange)
);
}
return(result);
}
public Vector3d CalcAccelerationEulerInPoint(Vector3d pos)
{
Vector3d result = new Vector3d();
for (int i = 0; i < attractorsCache.Count; i++)
{
if (attractorsCache[i].position == pos)
{
continue;
}
result += CelestialBodyUtils.AccelerationByAttractionForce(
pos,
attractorsCache[i].position,
attractorsCache[i].MG,
minAttractionRange,
Mathd.Min(maxAttractionRange, attractorsCache[i].maxAttractionRange)
);
}
return(result);
}
public void CalcAccelerationEulerForBody(CelestialBody body, double dt)
{
Vector3d result = Vector3d.zero;
for (int i = 0; i < attractorsCache.Count; i++)
{
if (attractorsCache[i] == body)
{
continue;
}
result += CelestialBodyUtils.AccelerationByAttractionForce(
body.position,
attractorsCache[i].position,
attractorsCache[i].MG,
minAttractionRange,
Mathd.Min(maxAttractionRange, attractorsCache[i].maxAttractionRange)
);
}
body.velocity += result * dt;
}
/// <summary>
/// Calculate and apply n-body gravitational acceleration to target body, using Euler algorythm.
/// In result body will change it's velocity according to global gravity.
/// </summary>
/// <param name="body">Target body.</param>
/// <param name="dt">Delta time.</param>
/// <param name="minRange">Minimal attraction range for attractors.</param>
/// <param name="maxRange">Maximal attraction range for attractors.</param>
/// <param name="allAttractors">List of all attractors on scene.</param>
public static void CalcAccelerationEulerForBody(CelestialBody body, double dt, double minRange, double maxRange, List <CelestialBody> allAttractors)
{
Vector3d result = Vector3d.zero;
for (int i = 0; i < allAttractors.Count; i++)
{
if (object.ReferenceEquals(allAttractors[i], body))
{
continue;
}
result += CelestialBodyUtils.AccelerationByAttractionForce(
body.Position,
allAttractors[i].Position,
allAttractors[i].MG,
minRange,
Mathd.Min(maxRange, allAttractors[i].MaxAttractionRange)
);
}
if (!result.isZero)
{
body.Velocity += result * dt;
}
}
