Movement with Mass Framework

Processing Movement with MassGameplay built-in resources

• Movement Trait

  Built-in MassGameplay Trait located At UE5/Engine/Plugins/Runtime/MassGameplay/Source/MassMovement

  Image
  .h

  UCLASS(meta = (DisplayName = "Movement"))
  class MASSMOVEMENT_API UMassMovementTrait : public UMassEntityTraitBase
  {
  	GENERATED_BODY()
  
  protected:
  	virtual void BuildTemplate(FMassEntityTemplateBuildContext& BuildContext, const UWorld& World) const override;
  
  	UPROPERTY(Category="Movement", EditAnywhere)
  	FMassMovementParameters Movement;
  };

  .cpp

  void UMassMovementTrait::BuildTemplate(FMassEntityTemplateBuildContext& BuildContext, const UWorld& World) const
  {
  	FMassEntityManager& EntityManager = UE::Mass::Utils::GetEntityManagerChecked(World);
  
  	BuildContext.RequireFragment<FAgentRadiusFragment>();
  	BuildContext.RequireFragment<FTransformFragment>();
  
  	BuildContext.AddFragment<FMassVelocityFragment>();
  	BuildContext.AddFragment<FMassForceFragment>();
  
  	const FConstSharedStruct MovementFragment = EntityManager.GetOrCreateConstSharedFragment(Movement);
  	BuildContext.AddConstSharedFragment(MovementFragment);
  }

  Check Built-in Movement processor to get knwoledge of processing the movement from the trait

• Fragments for movement

  As you can see, the built-in Movement Trait of MassGameplay plugin works with the 4 following fragments:

  FMassVelocityFragment

  Located at UE5/Engine/Plugins/Runtime/MassGameplay/Source/MassMovement

  USTRUCT()
  struct MASSMOVEMENT_API FMassVelocityFragment : public FMassFragment
  {
  	GENERATED_BODY()
  
  	FVector Value = FVector::ZeroVector;
  };

  FMassForceFragment

  Located at UE5/Engine/Plugins/Runtime/MassGameplay/Source/MassMovement

  USTRUCT()
  struct MASSMOVEMENT_API FMassForceFragment : public FMassFragment
  {
  	GENERATED_BODY()
  
  	FVector Value = FVector::ZeroVector;
  };

  FAgentRadiusFragment

  Located at UE5/Engine/Plugins/Runtime/MassGameplay/Source/MassCommon

  USTRUCT()
  struct MASSCOMMON_API FAgentRadiusFragment : public FMassFragment
  {
  	GENERATED_BODY()
  	UPROPERTY(EditAnywhere, Category = "")
  	float Radius = 40.f;
  };

  FTransformFragment

  Located at UE5/Engine/Plugins/Runtime/MassGameplay/Source/MassCommon

  USTRUCT()
  struct MASSCOMMON_API FTransformFragment : public FMassFragment
  {
  	GENERATED_BODY()
  
  	const FTransform& GetTransform() const { return Transform; }
  	void SetTransform(const FTransform& InTransform) { Transform = InTransform; }
  	FTransform& GetMutableTransform() { return Transform; }
  
  protected:
  	UPROPERTY(Transient)
  	FTransform Transform;
  };

• Movement Processor

  Built-in MassGameplay Processor located at UE5/Engine/Plugins/Runtime/MassGameplay/Source/MassMovement

  Now, as you know the fragments and their values, you can check how they are used for automatical processing of movement. The point is, in a case of using the built-in Movement Trait (MassGameplay), all you need for processing movements is to set (update) the traits values. You can do that e.g. from a custom Mass processor.

  .h

  UCLASS()
  class MASSMOVEMENT_API UMassApplyMovementProcessor : public UMassProcessor
  {
  	GENERATED_BODY()
  
  public:
  	UMassApplyMovementProcessor();
  
  protected:
  	virtual void ConfigureQueries() override;
  	virtual void Execute(FMassEntityManager& EntityManager, FMassExecutionContext& Context) override;
  
  private:
  	FMassEntityQuery EntityQuery;
  };

  .cpp

  UMassApplyMovementProcessor::UMassApplyMovementProcessor()
  	: EntityQuery(*this)
  {
  	ExecutionFlags = (int32)EProcessorExecutionFlags::All;
  	ExecutionOrder.ExecuteInGroup = UE::Mass::ProcessorGroupNames::Movement;
  	ExecutionOrder.ExecuteAfter.Add(UE::Mass::ProcessorGroupNames::Avoidance);
  }
  
  void UMassApplyMovementProcessor::ConfigureQueries()
  {
  	EntityQuery.AddRequirement<FMassVelocityFragment>(EMassFragmentAccess::ReadWrite);
  	EntityQuery.AddRequirement<FTransformFragment>(EMassFragmentAccess::ReadWrite);
  	EntityQuery.AddRequirement<FMassForceFragment>(EMassFragmentAccess::ReadWrite);
  	EntityQuery.AddTagRequirement<FMassOffLODTag>(EMassFragmentPresence::None);
  	EntityQuery.AddConstSharedRequirement<FMassMovementParameters>(EMassFragmentPresence::All);
  }
  
  void UMassApplyMovementProcessor::Execute(FMassEntityManager& EntityManager,
  													FMassExecutionContext& Context)
  {
  	// Clamp max delta time to avoid force explosion on large time steps (i.e. during initialization).
  	const float DeltaTime = FMath::Min(0.1f, Context.GetDeltaTimeSeconds());
  
  	QUICK_SCOPE_CYCLE_COUNTER(HighRes);
  
  	EntityQuery.ForEachEntityChunk(EntityManager, Context, [this, DeltaTime](FMassExecutionContext& Context)
  	{
  		const int32 NumEntities = Context.GetNumEntities();
  
  		const FMassMovementParameters& MovementParams = Context.GetConstSharedFragment<FMassMovementParameters>();
  
  		const TArrayView<FTransformFragment> LocationList = Context.GetMutableFragmentView<FTransformFragment>();
  		const TArrayView<FMassForceFragment> ForceList = Context.GetMutableFragmentView<FMassForceFragment>();
  		const TArrayView<FMassVelocityFragment> VelocityList = Context.GetMutableFragmentView<FMassVelocityFragment>();
  
  		for (int32 EntityIndex = 0; EntityIndex < NumEntities; ++EntityIndex)
  		{
  			FMassForceFragment& Force = ForceList[EntityIndex];
  			FMassVelocityFragment& Velocity = VelocityList[EntityIndex];
  			FTransform& CurrentTransform = LocationList[EntityIndex].GetMutableTransform();
  
  			// Update velocity from steering forces. (Force default value is ZeroVevtor)
  			Velocity.Value += Force.Value * DeltaTime;
  
  			FVector CurrentLocation = CurrentTransform.GetLocation();
  			CurrentLocation += Velocity.Value * DeltaTime;
  			CurrentTransform.SetTranslation(CurrentLocation);
  		}
  	});
  }