public void ResolveAtmopsherics(IMassiveBody body)
{
DVector2 difference = body.Position - Position;
double distance = difference.Length();
difference.Normalize();
double altitude = distance - body.SurfaceRadius;
// The object is in the atmosphere of body B
if (altitude < body.AtmosphereHeight)
{
var surfaceNormal = new DVector2(-difference.Y, difference.X);
double altitudeFromCenter = altitude + body.SurfaceRadius;
// Distance of circumference at this altitude ( c= 2r * pi )
double pathCirumference = 2 * Math.PI * altitudeFromCenter;
double rotationalSpeed = pathCirumference / body.RotationPeriod;
// Simple collision detection
if (altitude <= 0)
{
var normal = new DVector2(-difference.X, -difference.Y);
Position = body.Position + normal * (body.SurfaceRadius);
Velocity = (body.Velocity + surfaceNormal * rotationalSpeed);
Rotation = normal.Angle();
AccelerationN.X = -AccelerationG.X;
AccelerationN.Y = -AccelerationG.Y;
}
double atmosphericDensity = body.GetAtmosphericDensity(altitude);
DVector2 relativeVelocity = (body.Velocity + surfaceNormal * rotationalSpeed) - Velocity;
double velocityMagnitude = relativeVelocity.LengthSquared();
if (velocityMagnitude > 0)
{
relativeVelocity.Normalize();
// Drag ( Fd = 0.5pv^2dA )
DVector2 dragForce = relativeVelocity * (0.5 * atmosphericDensity * velocityMagnitude * DragCoefficient * CrossSectionalArea);
AccelerationD += dragForce / Mass;
}
}
}
public virtual void ResolveGravitation(IPhysicsBody other)
{
DVector2 difference = other.Position - Position;
double r2 = difference.LengthSquared();
double massDistanceRatio = other.Mass / r2;
// Ignore the force, the planet is too far away to matter
if (massDistanceRatio < 2500)
{
return;
}
difference.Normalize();
// Gravitation ( aG = G m1 / r^2 )
AccelerationG += difference * Constants.GravitationConstant * massDistanceRatio;
}
// Gets bodies sorted by distance that point the direction of the camera normal
private static List <Tuple <double, int> > GetSortedBodyDistances(int currentIndex, IList <IGravitationalBody> bodies, DVector2 cameraNormal)
{
DVector2 targetCenter = bodies[currentIndex].Position;
var bodiesByDistance = new List <Tuple <double, int> >();
for (int i = 0; i < bodies.Count; i++)
{
if (i == currentIndex)
{
continue;
}
var spaceCraft = bodies[i] as ISpaceCraft;
// Skip terminated bodies
if (spaceCraft != null && spaceCraft.Terminated)
{
continue;
}
DVector2 difference = bodies[i].Position - targetCenter;
double distance = difference.LengthSquared();
difference.Normalize();
// Only add bodies in the same direction as the camera normal
if (difference.Dot(cameraNormal) > 0)
{
bodiesByDistance.Add(new Tuple <double, int>(distance, i));
}
}
bodiesByDistance.Sort(Compare);
return(bodiesByDistance);
}
private static List <Tuple <double, int> > GetSortedBodyDistances(int currentIndex, IList <IGravitationalBody> bodies)
{
DVector2 targetCenter = bodies[currentIndex].Position;
var bodiesByDistance = new List <Tuple <double, int> >();
for (int i = 0; i < bodies.Count; i++)
{
if (i == currentIndex)
{
continue;
}
DVector2 difference = targetCenter - bodies[i].Position;
double distance = difference.LengthSquared();
bodiesByDistance.Add(new Tuple <double, int>(distance, i));
}
bodiesByDistance.Sort(Compare);
return(bodiesByDistance);
}
public void ResolveAtmopsherics(IMassiveBody body)
{
// Don't resolve drag for children
if (Parent != null)
{
return;
}
DVector2 difference = body.Position - Position;
double heightOffset = Children.Count > 0 ? TotalHeight - Height * 0.5 : Height * 0.5;
double distance = difference.Length() - heightOffset;
difference.Normalize();
double altitude = distance - body.SurfaceRadius;
// The spacecraft is in the bodies atmopshere
if (altitude < body.AtmosphereHeight)
{
var surfaceNormal = new DVector2(-difference.Y, difference.X);
double altitudeFromCenter = altitude + body.SurfaceRadius;
// Distance of circumference at this altitude ( c= 2r * pi )
double pathCirumference = 2 * Math.PI * altitudeFromCenter;
double rotationalSpeed = pathCirumference / body.RotationPeriod;
// Rough metric for staying on ground from frame to frame
if (altitude <= 0.0001)
{
_onGroundIterations = Math.Min(_onGroundIterations + 1, 10);
}
else
{
_onGroundIterations = Math.Max(_onGroundIterations - 1, 0);
}
// Simple collision detection
if (_onGroundIterations > 5)
{
OnGround = true;
var normal = new DVector2(-difference.X, -difference.Y);
Position = body.Position + normal * (body.SurfaceRadius + heightOffset);
Velocity = (body.Velocity + surfaceNormal * rotationalSpeed);
Pitch = normal.Angle();
AccelerationN.X = -AccelerationG.X;
AccelerationN.Y = -AccelerationG.Y;
AccelerationY = new DVector2(0, 0);
}
else
{
OnGround = false;
}
double atmosphericDensity = body.GetAtmosphericDensity(altitude);
DVector2 relativeVelocity = (body.Velocity + surfaceNormal * rotationalSpeed) - Velocity;
double velocityMagnitude = relativeVelocity.LengthSquared();
if (velocityMagnitude > 0)
{
double speed = relativeVelocity.Length();
// Heating
double qConv = 1.83e-4 * Math.Pow(speed, 3) * Math.Sqrt(atmosphericDensity / (Width * 0.5));
double qRad = 3.2e-22 * Math.Pow(speed, 8) * Math.Pow(atmosphericDensity, 1.2) * Math.Sqrt((Width * 0.5));
HeatingRate = qConv + qRad;
relativeVelocity.Normalize();
double formDragCoefficient = TotalFormDragCoefficient();
double skinFrictionCoefficient = TotalSkinFrictionCoefficient();
double liftCoefficient = TotalLiftCoefficient();
double formDragTerm = formDragCoefficient * TotalFormDragArea();
double skinFrictionTerm = skinFrictionCoefficient * TotalSkinFrictionArea();
double dragTerm = formDragTerm;
if (!double.IsNaN(skinFrictionTerm))
{
dragTerm += skinFrictionTerm;
}
double liftTerm = liftCoefficient * TotalLiftArea();
double turnTerm = 0;
if (Settings.Default.UseTheTurnForce)
{
turnTerm = liftTerm * Math.Sin(Roll);
liftTerm *= Math.Cos(Roll);
}
// Form Drag ( Fd = 0.5pv^2dA )
// Skin friction ( Fs = 0.5CfpV^2S )
DVector2 drag = relativeVelocity * (0.5 * atmosphericDensity * velocityMagnitude * dragTerm);
DVector2 lift = relativeVelocity * (0.5 * atmosphericDensity * velocityMagnitude * liftTerm);
AccelerationD = drag / Mass;
DVector2 accelerationLift = lift / Mass;
double alpha = GetAlpha();
double halfPi = Math.PI / 2;
bool isRetrograde = alpha > halfPi || alpha < -halfPi;
if (Settings.Default.UseTheTurnForce && isRetrograde)
{
AccelerationL.X -= accelerationLift.Y;
AccelerationL.Y += accelerationLift.X;
}
else
{
AccelerationL.X += accelerationLift.Y;
AccelerationL.Y -= accelerationLift.X;
}
}
}
else
{
HeatingRate = 0;
}
}
public void ResolveAtmopsherics(IMassiveBody body)
{
// Don't resolve drag for children
if (Parent != null)
{
return;
}
DVector2 difference = body.Position - Position;
double distance = difference.Length();
difference.Normalize();
double altitude = distance - body.SurfaceRadius;
// The spacecraft is in the bodies atmopshere
if (altitude < body.AtmosphereHeight)
{
var surfaceNormal = new DVector2(-difference.Y, difference.X);
double altitudeFromCenter = altitude + body.SurfaceRadius;
// Distance of circumference at this altitude ( c= 2r * pi )
double pathCirumference = 2 * Math.PI * altitudeFromCenter;
double rotationalSpeed = pathCirumference / body.RotationPeriod;
// Simple collision detection
if (altitude <= 0)
{
var normal = new DVector2(-difference.X, -difference.Y);
Position = body.Position + normal * (body.SurfaceRadius);
Velocity = (body.Velocity + surfaceNormal * rotationalSpeed);
Rotation = normal.Angle();
AccelerationN.X = -AccelerationG.X;
AccelerationN.Y = -AccelerationG.Y;
}
double atmosphericDensity = body.GetAtmosphericDensity(altitude);
DVector2 relativeVelocity = (body.Velocity + surfaceNormal * rotationalSpeed) - Velocity;
double velocity = relativeVelocity.Length();
double velocitySquared = relativeVelocity.LengthSquared();
if (velocitySquared > 0)
{
double speed = relativeVelocity.Length();
// Heating
HeatingRate = 1.83e-4 * Math.Pow(speed, 3) * Math.Sqrt(atmosphericDensity / (Width * 0.5));
relativeVelocity.Normalize();
double dragTerm = TotalDragCoefficient() * TotalDragArea();
// Drag ( Fd = 0.5pv^2dA )
DVector2 dragForce = relativeVelocity * (0.5 * atmosphericDensity * velocitySquared * dragTerm);
AccelerationD += dragForce / Mass;
double reynoldsNumber = (velocity * Height) / body.GetAtmosphericViscosity(altitude);
double frictionCoefficient = 0.455 / Math.Pow(Math.Log10(reynoldsNumber), 2.58);
double frictionTerm = frictionCoefficient * TotalSurfaceArea();
// Skin friction ( Fs = 0.5CfpV^2S )
DVector2 skinFriction = relativeVelocity * (0.5 * atmosphericDensity * velocitySquared * frictionTerm);
AccelerationD += skinFriction / Mass;
}
}
else
{
HeatingRate = 0;
}
}
[MethodImpl(MethodImplOptions.AggressiveInlining)] public static double Length(this DVector2 v) => v.LengthSquared().Sqrt();
