FVector UKismetMathLibrary::ClampVectorSize(FVector A, float Min, float Max)
{
return A.GetClampedToSize(Min, Max);
}
// Runs calculations on friction component, applies friction force to effected component and returns reaction forces(forces that can effect track or a wheel)
void UMMTFrictionComponent::ApplyFriction(const FVector& ContactPointLocation, const FVector& ContactPointNormal, const FVector& InducedVelocity, const FVector& PreNormalForceAtPoint,
const EPhysicalSurface& PhysicalSurface, const float& NumberOfContactPoints, const float& DeltaTime, FVector& NormalizedReactionForce, FVector& RollingFrictionForce)
{
// Gather stats
SCOPE_CYCLE_COUNTER(STAT_MMTFrictionApply);
float NormalForceAtContactPoint = PreNormalForceAtPoint.ProjectOnTo(ContactPointNormal).Size();
// Check if Effected Component Mesh reference is valid and escape early otherwise
if (!IsValid(EffectedComponentMesh))
{
GEngine->AddOnScreenDebugMessage(-1, 15.0f, FColor::Red, FString::Printf(TEXT("%s->%s component's EffectedComponentMesh reference is invalid!"), *GetOwner()->GetName(), *GetName()));
UE_LOG(LogTemp, Warning, TEXT("%s->%s component's EffectedComponentMesh reference is invalid!"), *GetOwner()->GetName(), *GetName());
NormalizedReactionForce = FVector::ZeroVector;
RollingFrictionForce = FVector::ZeroVector;
return;
}
//Find relative velocity of the friction surface and ground/another object at point
FVector RelativeVelocityAtPoint = EffectedComponentMesh->GetPhysicsLinearVelocityAtPoint(ContactPointLocation) + InducedVelocity + FrictionSurfaceVelocity;
RelativeVelocityAtPoint = RelativeVelocityAtPoint.VectorPlaneProject(RelativeVelocityAtPoint, ContactPointNormal);
//filter out oscillations when vehicle is standing still but friction overshoots
RelativeVelocityAtPoint = (PrevRelativeVelocityAtPoint + RelativeVelocityAtPoint) * 0.5;
PrevRelativeVelocityAtPoint = RelativeVelocityAtPoint;
// early exit if velocity is too low to consider as vehicle most likely standing still
if (RelativeVelocityAtPoint.Size() < 1.0f)
{
NormalizedReactionForce = FVector::ZeroVector;
RollingFrictionForce = FVector::ZeroVector;
return;
}
//Calculate static and kinetic friction coefficients, taking into account velocity direction and friction ellipse
float MuStatic;
float MuKinetic;
UMMTBPFunctionLibrary::GetMuFromFrictionElipse(RelativeVelocityAtPoint.GetSafeNormal(), ReferenceFrameTransform.TransformVector(FVector(1.0f, 1.0f, 1.0f)),
MuXStatic, MuXKinetic, MuYStatic, MuYKinetic, MuStatic, MuKinetic);
//Calculate "stopping force" which is amount of force necessary to completely remove velocity of the object
FVector StoppingForce = ((RelativeVelocityAtPoint * (-1.0f) * EffectedComponentMesh->GetMass()) / DeltaTime) / NumberOfContactPoints;
//Static friction threshold
float MuStaticByLoad = NormalForceAtContactPoint * MuStatic;
//Friction Force that will be applied to effected mesh component
FVector ApplicationForce;
if (StoppingForce.Size() >= MuStaticByLoad)
{
ApplicationForce = StoppingForce.GetClampedToSize(0.0f, NormalForceAtContactPoint * MuKinetic);
if (IsDebugMode)
{
DrawDebugString(GetWorld(), ContactPointLocation, FString("Kinetic Friction"), nullptr, FColor::Magenta, 0.0f, false);
}
}
else
{
ApplicationForce = StoppingForce.GetClampedToSize(0.0f, MuStaticByLoad);
if (IsDebugMode)
{
DrawDebugString(GetWorld(), ContactPointLocation, FString("Static Friction"), nullptr, FColor::Red, 0.0f, false);
}
}
//Apply friction force
UMMTBPFunctionLibrary::MMTAddForceAtLocationComponent(EffectedComponentMesh, ApplicationForce, ContactPointLocation);
//Calculate Reaction force
NormalizedReactionForce = (ApplicationForce * (-1.0f)) / EffectedComponentMesh->GetMass();
//Calculate Rolling Friction
float RollingFrictionCoefficient = FPhysicalSurfaceRollingFrictionCoefficient().RollingFrictionCoefficient;
for (int32 i = 0; i < PhysicsSurfaceResponse.Num(); i++)
{
if (PhysicsSurfaceResponse[i].PhysicalSurface == PhysicalSurface)
{
RollingFrictionCoefficient = PhysicsSurfaceResponse[i].RollingFrictionCoefficient;
break;
}
}
RollingFrictionForce = RelativeVelocityAtPoint.GetSafeNormal() * NormalForceAtContactPoint * RollingFrictionCoefficient;
if (IsDebugMode)
{
DrawDebugLine(GetWorld(), ContactPointLocation, ContactPointLocation + ApplicationForce * 0.005f, FColor::Yellow, false, 0.0f, 0, 3.0f);
DrawDebugLine(GetWorld(), ContactPointLocation, ContactPointLocation + RollingFrictionForce * 0.005f, FColor::Green, false, 0.0f, 0, 3.0f);
DrawDebugString(GetWorld(), ContactPointLocation+FVector(0.0f, 0.0f, 50.0f), (PhysicalSurfaceEnum ? PhysicalSurfaceEnum->GetEnumName(PhysicalSurface) : FString("<Invalid Enum>")), nullptr, FColor::Cyan, 0.0f, false);
//DrawDebugString(GetWorld(), ContactPointLocation + FVector(0.0f, 0.0f, 25.0f), FString("Normal Force: ") + FString::SanitizeFloat(NormalForceAtContactPoint), nullptr, FColor::Turquoise, 0.0f, false);
}
}
