Skip to main content

Quick start — C++

Build dependencies​

PublicDependencyModuleNames.AddRange(new string[]
{
    "Core", "CoreUObject", "Engine",
    "GameplayTags",
    "MotionWarping",     // for the rider's warping component
    "EDMountingCore",
    "EDMountingVehicles" // only if you use AEDMountableVehicle
});

The rider​

#include "Components/EDRiderComponent.h"
#include "MotionWarpingComponent.h"

AMyCharacter::AMyCharacter()
{
    Rider = CreateDefaultSubobject<UEDRiderComponent>(TEXT("Rider"));
    MotionWarping = CreateDefaultSubobject<UMotionWarpingComponent>(TEXT("MotionWarping"));
}

That is the entire rider-side setup. The interaction key:

void AMyCharacter::OnInteract()
{
    const FEDMountResult Result = Rider->IsMounted()
        ? Rider->RequestDismount()
        : Rider->RequestMountNearest();

    if (!Result.bSuccess)
    {
        // Every refusal names itself, and every name has localised text.
        ShowMessage(UEDMountingLibrary::GetFailureText(Result.Failure));
    }
}

and the movement axis:

void AMyCharacter::OnMove(const FInputActionValue& Value)
{
    const FVector2D Axis = Value.Get<FVector2D>();

    if (Rider->IsSeated())
    {
        // A no-op unless this character is in a seat tagged Mount.Role.Driver.
        Rider->ApplyDriveInput(Axis, FMath::Max(0.f, Axis.Y), FMath::Max(0.f, -Axis.Y), bHandbrakeHeld);
        return;
    }

    // ... ordinary walking
}
Bind Completed as well as Triggered

Chaos holds the last input it was given. If you only forward while the key is held, releasing W leaves the car at full throttle.

The mount​

#include "Components/EDMountableComponent.h"
#include "Components/EDMountPointComponent.h"
#include "Interfaces/EDMountableInterface.h"
#include "System/EDMountingTags.h"

class AMyVehicle : public AWheeledVehiclePawn, public IEDMountableInterface
{
    GENERATED_BODY()
public:
    AMyVehicle();
    virtual void ApplyDriverInput_Implementation(APawn* Driver, const FVector2D& MoveInput,
        float Throttle, float Brake, bool bHandbrake) override;

protected:
    UPROPERTY(VisibleAnywhere) TObjectPtr<UEDMountableComponent> Mountable;
    UPROPERTY(VisibleAnywhere) TObjectPtr<UEDMountPointComponent> DriverSeat;
};
AMyVehicle::AMyVehicle()
{
    Mountable = CreateDefaultSubobject<UEDMountableComponent>(TEXT("Mountable"));

    DriverSeat = CreateDefaultSubobject<UEDMountPointComponent>(TEXT("DriverSeat"));
    DriverSeat->SetupAttachment(GetMesh());
    DriverSeat->SeatName = TEXT("Driver");
    DriverSeat->RoleTag = EDMountingTags::Mount_Role_Driver;
    DriverSeat->SetRelativeLocation(FVector(30.f, -38.f, 55.f));

    // A door on the near side. Leave EntryPoints empty and the framework derives a
    // left/right pair from the vehicle's bounds, which is a fine starting point.
    FEDEntryPoint LeftDoor;
    LeftDoor.SideTag = EDMountingTags::Mount_Entry_Left;
    LeftDoor.RelativeTransform = FTransform(FRotator::ZeroRotator, FVector(0.f, -115.f, -35.f));
    DriverSeat->EntryPoints.Add(LeftDoor);
}

void AMyVehicle::ApplyDriverInput_Implementation(APawn* /*Driver*/, const FVector2D& MoveInput,
    float Throttle, float Brake, bool bHandbrake)
{
    UChaosVehicleMovementComponent* Movement = GetVehicleMovementComponent();
    Movement->SetSteeringInput(MoveInput.X);
    Movement->SetThrottleInput(Throttle);
    Movement->SetBrakeInput(Brake);
    Movement->SetHandbrakeInput(bHandbrake);
}
There is a base class for this

AEDMountableVehicle already has the mountable component, the driver's seat and the input forwarding. Derive from it and you skip all of the above. See Vehicles.

Addressing a seat​

Look it up once, keep the handle:

// At setup
GunnerSeat = Mountable->FindSeatByName(TEXT("Gunner"));

// Later, forever
Rider->RequestChangeSeat(GunnerSeat);

FEDSeatHandle is a stable id, valid on every machine, unchanged when seats come and go. It is the only way to name a seat — see Seats for why that matters.

Reacting to things​

Rider->OnMountPhaseChanged.AddDynamic(this, &AMyCharacter::OnPhaseChanged);   // everywhere
Rider->OnMountFailed.AddDynamic(this, &AMyCharacter::OnMountFailed);         // locally
Mountable->OnSeatOccupancyChanged.AddDynamic(this, &AMyHud::OnSeatChanged);  // everywhere

Phase and occupancy fire on every machine, simulated proxies included, so a HUD showing who is in which seat needs no replication of its own.

Placing a pawn in a seat from script​

FEDMountRequest Request;
Request.MountActor = Vehicle;
Request.DesiredSeat = Mountable->FindSeatByName(TEXT("Driver"));
Request.bAllowSeatFallback = false;  // that seat or nothing
Request.bInstant = true;             // no animation, and no distance check

Rider->RequestMountWithOptions(Request);

bInstant bypasses reach as well — an actor placed into a seat by script is not walking there. This is the path for spawning already-seated, for save-game restore, and for cutscenes.

Next​

Last updated on