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

  .cpp

  void UMassMovementTrait::BuildTemplate(FMassEntityTemplateBuildContext& BuildContext, const UWorld& World) const
  {
  	FMassEntityManager& EntityManager = UE::Mass::Utils::GetEntityManagerChecked(World);
  
  	BuildContext.<mark>RequireFragment&lt;FAgentRadiusFragment&gt;</mark>();
  	BuildContext.<mark>RequireFragment&lt;FTransformFragment&gt;</mark>();
  
  	BuildContext.<mark>AddFragment&lt;FMassVelocityFragment&gt;</mark>();
  	BuildContext.<mark>AddFragment&lt;FMassForceFragment&gt;</mark>();
  
  	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()
  
  	<mark>FVector Value = FVector::ZeroVector;</mark>
  };

  FMassForceFragment

  FAgentRadiusFragment

  FTransformFragment

• 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

  .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.<mark>AddRequirement&lt;FMassVelocityFragment&gt;</mark>(EMassFragmentAccess::ReadWrite);
  	EntityQuery.<mark>AddRequirement&lt;FTransformFragment&gt;</mark>(EMassFragmentAccess::ReadWrite);
  	EntityQuery.<mark>AddRequirement&lt;FMassForceFragment&gt;</mark>(EMassFragmentAccess::ReadWrite);
  	EntityQuery.<mark>AddTagRequirement&lt;FMassOffLODTag&gt;</mark>(EMassFragmentPresence::None);
  	EntityQuery.<mark>AddConstSharedRequirement&lt;FMassMovementParameters&gt;</mark>(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&lt;FMassMovementParameters&gt;();
  
  		const TArrayView&lt;FTransformFragment&gt; LocationList = Context.GetMutableFragmentView&lt;FTransformFragment&gt;();
  		const TArrayView&lt;FMassForceFragment&gt; ForceList = Context.GetMutableFragmentView&lt;FMassForceFragment&gt;();
  		const TArrayView&lt;FMassVelocityFragment&gt; VelocityList = Context.GetMutableFragmentView&lt;FMassVelocityFragment&gt;();
  
  		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)
  			<mark>Velocity.Value += Force.Value * DeltaTime;</mark>
  
  			FVector CurrentLocation = CurrentTransform.GetLocation();
  			<mark>CurrentLocation += Velocity.Value * DeltaTime;</mark>
  			<mark>CurrentTransform.SetTranslation(CurrentLocation);</mark>
  		}
  	});
  }