private BiVector3 CalculateAerodynamicForces(Vector3 velocity, Vector3 angularVelocity, Vector3 wind, float airDensity, Vector3 centerOfMass)
{
BiVector3 forceAndTorque = new BiVector3();
foreach (var surface in aerodynamicSurfaces)
{
Vector3 relativePosition = surface.transform.position - centerOfMass;
forceAndTorque += surface.CalculateForces(-velocity + wind
- Vector3.Cross(angularVelocity,
relativePosition),
airDensity, relativePosition);
}
return(forceAndTorque);
}
private void FixedUpdate()
{
BiVector3 forceAndTorqueThisFrame =
CalculateAerodynamicForces(rb.velocity, rb.angularVelocity, Vector3.zero, 1.2f, rb.worldCenterOfMass);
Vector3 velocityPrediction = PredictVelocity(forceAndTorqueThisFrame.p);
Vector3 angularVelocityPrediction = PredictAngularVelocity(forceAndTorqueThisFrame.q);
BiVector3 forceAndTorquePrediction =
CalculateAerodynamicForces(velocityPrediction, angularVelocityPrediction, Vector3.zero, 1.2f, rb.worldCenterOfMass);
currentForceAndTorque = (forceAndTorqueThisFrame + forceAndTorquePrediction) * 0.5f;
rb.AddForce(currentForceAndTorque.p);
rb.AddTorque(currentForceAndTorque.q);
rb.AddForce(transform.forward * thrust * thrustPercent);
}
public BiVector3 CalculateForces(Vector3 worldAirVelocity, float airDensity, Vector3 relativePosition)
{
BiVector3 forceAndTorque = new BiVector3();
if (!gameObject.activeInHierarchy || config == null)
{
return(forceAndTorque);
}
if (!initialized)
{
Initialize();
}
Vector3 airVelocity = transform.InverseTransformDirection(worldAirVelocity);
airVelocity = new Vector3(airVelocity.x, airVelocity.y);
Vector3 dragDirection = transform.TransformDirection(airVelocity.normalized);
Vector3 liftDirection = Vector3.Cross(dragDirection, transform.forward);
float dynamicPressure = 0.5f * airDensity * airVelocity.sqrMagnitude;
float angleOfAttack = Mathf.Atan2(airVelocity.y, -airVelocity.x);
IsAtStall = !(angleOfAttack <stallAngleHigh && angleOfAttack> stallAngleLow);
Vector3 aerodynamicCoefficients = CalculateCoefficients(angleOfAttack);
CurrentLift = liftDirection * aerodynamicCoefficients.x * dynamicPressure * area;
CurrentDrag = dragDirection * aerodynamicCoefficients.y * dynamicPressure * area;
CurrentTorque = -transform.forward * aerodynamicCoefficients.z * dynamicPressure * area * config.chord;
forceAndTorque.p += CurrentDrag + CurrentLift;
forceAndTorque.q += Vector3.Cross(relativePosition, forceAndTorque.p);
forceAndTorque.q += CurrentTorque;
return(forceAndTorque);
}
public BiVector3 CalculateForces(Vector3 worldAirVelocity, float airDensity, Vector3 relativePosition)
{
BiVector3 forceAndTorque = new BiVector3();
if (!gameObject.activeInHierarchy || config == null)
{
return(forceAndTorque);
}
// Accounting for aspect ratio effect on lift coefficient.
float correctedLiftSlope = config.liftSlope * config.aspectRatio /
(config.aspectRatio + 2 * (config.aspectRatio + 4) / (config.aspectRatio + 2));
// Calculating flap deflection influence on zero lift angle of attack
// and angles at which stall happens.
float theta = Mathf.Acos(2 * config.flapFraction - 1);
float flapEffectivness = 1 - (theta - Mathf.Sin(theta)) / Mathf.PI;
float deltaLift = correctedLiftSlope * flapEffectivness * FlapEffectivnessCorrection(flapAngle) * flapAngle;
float zeroLiftAoaBase = config.zeroLiftAoA * Mathf.Deg2Rad;
float zeroLiftAoA = zeroLiftAoaBase - deltaLift / correctedLiftSlope;
float stallAngleHighBase = config.stallAngleHigh * Mathf.Deg2Rad;
float stallAngleLowBase = config.stallAngleLow * Mathf.Deg2Rad;
float clMaxHigh = correctedLiftSlope * (stallAngleHighBase - zeroLiftAoaBase) + deltaLift * LiftCoefficientMaxFraction(config.flapFraction);
float clMaxLow = correctedLiftSlope * (stallAngleLowBase - zeroLiftAoaBase) + deltaLift * LiftCoefficientMaxFraction(config.flapFraction);
float stallAngleHigh = zeroLiftAoA + clMaxHigh / correctedLiftSlope;
float stallAngleLow = zeroLiftAoA + clMaxLow / correctedLiftSlope;
// Calculating air velocity relative to the surface's coordinate system.
// Z component of the velocity is discarded.
Vector3 airVelocity = transform.InverseTransformDirection(worldAirVelocity);
airVelocity = new Vector3(airVelocity.x, airVelocity.y);
Vector3 dragDirection = transform.TransformDirection(airVelocity.normalized);
Vector3 liftDirection = Vector3.Cross(dragDirection, transform.forward);
float area = config.chord * config.span;
float dynamicPressure = 0.5f * airDensity * airVelocity.sqrMagnitude;
float angleOfAttack = Mathf.Atan2(airVelocity.y, -airVelocity.x);
Vector3 aerodynamicCoefficients = CalculateCoefficients(angleOfAttack,
correctedLiftSlope,
zeroLiftAoA,
stallAngleHigh,
stallAngleLow);
Vector3 lift = liftDirection * aerodynamicCoefficients.x * dynamicPressure * area;
Vector3 drag = dragDirection * aerodynamicCoefficients.y * dynamicPressure * area;
Vector3 torque = -transform.forward * aerodynamicCoefficients.z * dynamicPressure * area * config.chord;
forceAndTorque.p += lift + drag;
forceAndTorque.q += Vector3.Cross(relativePosition, forceAndTorque.p);
forceAndTorque.q += torque;
#if UNITY_EDITOR
// For gizmos drawing.
IsAtStall = !(angleOfAttack <stallAngleHigh && angleOfAttack> stallAngleLow);
CurrentLift = lift;
CurrentDrag = drag;
CurrentTorque = torque;
#endif
return(forceAndTorque);
}
