//Add all forces that act on the squares below the water
void AddUnderWaterForces()
{
//The resistance coefficient - same for all triangles
float Cf = BoatPhysicsMath.ResistanceCoefficient(
rhoWater,
boatRB.velocity.magnitude,
modifyBoatMesh.CalculateUnderWaterLength());
//To calculate the slamming force we need the velocity at each of the original triangles
List <SlammingForceData> slammingForceData = modifyBoatMesh.slammingForceData;
CalculateSlammingVelocities(slammingForceData);
//Need this data for slamming forces
float boatArea = modifyBoatMesh.boatArea;
float boatMass = 1f; //Replace this line with your boat's total mass
//To connect the submerged triangles with the original triangles
List <int> indexOfOriginalTriangle = modifyBoatMesh.indexOfOriginalTriangle;
//Get all triangles
List <TriangleData> underWaterTriangleData = modifyBoatMesh.underWaterTriangleData;
for (int i = 0; i < underWaterTriangleData.Count; i++)
{
TriangleData triangleData = underWaterTriangleData[i];
//Calculate the forces
Vector3 forceToAdd = Vector3.zero;
//Force 1 - The hydrostatic force (buoyancy)
forceToAdd += BoatPhysicsMath.BuoyancyForce(rhoWater, triangleData);
//Force 2 - Viscous Water Resistance
forceToAdd += BoatPhysicsMath.ViscousWaterResistanceForce(rhoWater, triangleData, Cf);
//Force 3 - Pressure drag
forceToAdd += BoatPhysicsMath.PressureDragForce(triangleData);
//Force 4 - Slamming force
//Which of the original triangles is this triangle a part of
int originalTriangleIndex = indexOfOriginalTriangle[i];
SlammingForceData slammingData = slammingForceData[originalTriangleIndex];
forceToAdd += BoatPhysicsMath.SlammingForce(slammingData, triangleData, boatArea, boatMass);
//Add the forces to the boat
boatRB.AddForceAtPosition(forceToAdd, triangleData.center);
//Debug
//Normal
//Debug.DrawRay(triangleData.center, triangleData.normal * 3f, Color.white);
//Buoyancy
//Debug.DrawRay(triangleData.center, BoatPhysicsMath.BuoyancyForce(rhoWater, triangleData).normalized * -3f, Color.blue);
//Velocity
//Debug.DrawRay(triangleCenter, triangleVelocityDir * 3f, Color.black);
//Viscous Water Resistance
//Debug.DrawRay(triangleCenter, viscousWaterResistanceForce.normalized * 3f, Color.black);
}
}
//Force 3 - Slamming Force (Water Entry Force)
public static Vector3 SlammingForce(SlammingForceData slammingData, TriangleData triangleData, float boatArea, float boatMass)
{
//To capture the response of the fluid to sudden accelerations or penetrations
//Add slamming if the normal is in the same direction as the velocity (the triangle is not receding from the water)
//Also make sure thea area is not 0, which it sometimes is for some reason
if (triangleData.cosTheta < 0f || slammingData.originalArea <= 0f)
{
return(Vector3.zero);
}
//Step 1 - Calculate acceleration
//Volume of water swept per second
Vector3 dV = slammingData.submergedArea * slammingData.velocity;
Vector3 dV_previous = slammingData.previousSubmergedArea * slammingData.previousVelocity;
//Calculate the acceleration of the center point of the original triangle (not the current underwater triangle)
//But the triangle the underwater triangle is a part of
Vector3 accVec = (dV - dV_previous) / (slammingData.originalArea * Time.fixedDeltaTime);
//The magnitude of the acceleration
float acc = accVec.magnitude;
//Debug.Log(slammingForceData.originalArea);
//Step 2 - Calculate slamming force
// F = clamp(acc / acc_max, 0, 1)^p * cos(theta) * F_stop
// p - power to ramp up slamming force - should be 2 or more
// F_stop = m * v * (2A / S)
// m - mass of the entire boat
// v - velocity
// A - this triangle's area
// S - total surface area of the entire boat
Vector3 F_stop = boatMass * triangleData.velocity * ((2f * triangleData.area) / boatArea);
//float p = DebugPhysics.current.p;
//float acc_max = DebugPhysics.current.acc_max;
float p = 2f;
float acc_max = acc;
float slammingCheat = DebugPhysics.current.slammingCheat;
Vector3 slammingForce = Mathf.Pow(Mathf.Clamp01(acc / acc_max), p) * triangleData.cosTheta * F_stop * slammingCheat;
//Vector3 slammingForce = Vector3.zero;
//Debug.Log(slammingForce);
//The force acts in the opposite direction
slammingForce *= -1f;
slammingForce = CheckForceIsValid(slammingForce, "Slamming");
return(slammingForce);
}