Animate Custom Actors in the Unreal Editor

Follow these steps to animate a custom actor in the Unreal^® Editor. Before you start, make sure you that you have Visual Studio^® 2022 and the Vehicle Dynamics Blockset™ Interface for Unreal Engine^® Projects support package installed on your machine. For more information, see Install Support Package and Configure Environment.

Additionally, make sure that:

• You are comfortable coding with C++ in Unreal Engine.

• Your Unreal Editor C++ project contains a skeletal actor mesh. This example uses a bicycle mesh.

  

This examples provides the workflow for animating a bicycle actor. The general workflow is adapted from the Unreal Engine Vehicle User Guide.

Set Up Simulink Model

Step 1: Set Up Simulink Model

Open a new Simulink^® model and add these blocks:

• Two Ramp blocks

• Constant block

• Simulation 3D Actor Transform Set block

• Simulation 3D Scene Configuration block

Connect and name the blocks as shown.

Step 2: Configure Blocks

Configure blocks with these parameter settings.

Block	Parameter Settings
Simulation 3D Scene Configuration	Scene source — Unreal Editor Project — Name and location of the installed support package project file, for example, C:\Local\AutoVrtlEnv\AutoVrtlEnv.uproject. Scene view — Scene Origin
Simulation 3D Actor Transform Set	Actor Setup tab: Tag for actor in 3D scene, ActorTag — Bike1 Note This tag should match the Unreal Editor tag name in Step 6: Instantiate the Bicycle Actor. Number of parts per actor to set, NumberOfParts — 3 Initial Values tab: Initial array values to translate actor per part, Translation — [0 0 0;0 0 0;0 0 0] Initial array values to rotate actor per part, Rotation — [0 0 0;0 0 0;0 0 0] Initial array values to scale actor per part, Scale — [1 1 1;1 1 1;1 1 1]
Translation Ramp	Slope — [0.35 0 0;0 0 0;0 0 0]
Rotation Ramp	Slope — [0 0 0;0 -pi/5 0;0 -pi/5 0]
Scale Constant	Constant value — [1 1 1;1 1 1;1 1 1]

Set Up Unreal Editor to Animate Bicycle

Step 3: Set Up Animation Instance

1. In your Simulink model, use the Simulation 3D Scene Configuration block Open Unreal Editor parameter to open the Unreal Editor.

2. Select Tools > New C++ Class. In the Choose Parent Class dialog box, select All Classes. Search for AnimInst. Select the AnimInstance and click Next.

   

3. Name the new C++ class SimulinkBikeAnimInst. Select Public. Click Create Class.

   

4. In Visual Studio 2022, open the C:\Local\AutoVrtlEnv\AutoVrtlEnv.sln file. Navigate to the SimulinkBikeAnimInst.cpp and SimulinkBikeAnimInst.h source files.

   

   Edit the files as shown.

   Tip

   For this example, the code includes FWheelRotation and RWheelRotation properties to animate the bicycle wheel rotation. You can add additional properties to animate other parts of the bicycle.

    Code: SimulinkBikeAnimInst.h

   // Copyright 2019 The MathWorks, Inc.
   #pragma once
    
   #include "CoreMinimal.h"
   #include "Animation/AnimInstance.h"
   #include "SimulinkBikeAnimInst.generated.h"
    
   /**
   *
   */
   UCLASS(transient, Blueprintable, hideCategories = AnimInstance, BlueprintType)
   class AUTOVRTLENV_API USimulinkBikeAnimInst : public UAnimInstance
   {
       GENERATED_UCLASS_BODY()
   public:
       UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = WheelRotation)
           float FWheelRotation;
    
       UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = WheelRotation)
           float RWheelRotation;
   };

    Code: SimulinkBikeAnimInst.cpp

   // Copyright 2019 The MathWorks, Inc.
   #include "SimulinkBikeAnimInst.h"
    
   USimulinkBikeAnimInst::USimulinkBikeAnimInst(const FObjectInitializer& ObjectInitializer)
       : Super(ObjectInitializer) {
       FWheelRotation = 0.0f;
       RWheelRotation = 0.0f;
   }

5. In the Unreal Editor click Compile.

   

   If there are errors, close the Unreal Editor. In Visual Studio, under Build, select clean solution and select Local Windows Debugger. The Unreal Editor opens.

Step 4: Create Animation Blueprint

1. In the Unreal Editor, on the Content Browser tab, under Settings, select Show Engine Content and Show Plugin Content.

   

2. Add the animation mesh. On the Content Browser tab, navigate to MathWorks Interface Content > Vehicles > Bicyclist > Meshes.

   

3. Right-click Meshes and select Add/Import Content > Animation > Animation Blueprint.

   

4. In the Create Animation Blueprint dialog box, select:

   • Parent Class: SimulinkBikeAnimInst

     

   • Target Skeleton: SK_Bicycle_Skeleton

     

   Click Create.

5. Name the blueprint BikeAnimation. Right-click and select Save.

   

6. Double-click BikeAnimation to open the BikeAnimation blueprint. Make the connections as shown.

   

   Note

   For FWheel Rotation and RWheel Rotation, select Get FWheel Rotation and Get RWheel Rotation blueprint nodes, respectively.

   For both front and rear wheels, make sure that you set:

   • Bone to Modify to the correct bone

   • Rotation Mode to Replace Existing

   • Rotation Space to Bone Space

   

7. Compile and save the blueprint.

Step 5: Create Bicycle Actor C++ Class

1. In the Unreal Editor, on the Content Browser tab, under View Options, select Show Engine Content and Show Plugin Content.

   

2. From the MathWorks Interface C++ Classes folder, select Sim3dActor.

   

   Right-click and select Create C++ class derived from Sim3dActor.

   

   Tip

   If you do not see the MathWorks Interface C++ Classes folder, use these steps to check that you have the MathWorks Interface plugin installed and enabled:

   1. In the Unreal Editor toolbar, select Edit > Plugins.

   2. In the Plugins window, verify that the MathWorks Interface plugin is listed in the installed window. If the plugin is not already enabled, select the Enabled check box.

   3. Close the editor and reopen it from Simulink.

3. Name the new Sim3dActor BicycleActor. Select Public. Click Create Class. Close Unreal Editor.

   

4. In Visual Studio, navigate to BicycleActor.h and BicycleActor.cpp.

   

   Edit the files as shown.

   Tip

   For this example, the code includes logic to animate the bike body (BIKE_BODY), front wheel (FRONT_WHEEL), and rear wheel (REAR_WHEEL). You can add additional logic to animate other parts of the bicycle.

    Code: BicycleActor.h

   // Copyright 2019 The MathWorks, Inc.
   #pragma once
    
   #include "CoreMinimal.h"
   #include "Sim3dActor.h"
   #include "BicycleActor.generated.h"
    
    
   UCLASS()
   class AUTOVRTLENV_API ABicycleActor : public ASim3dActor
   {
       GENERATED_BODY()
    
       // Reference to animation blueprint and skeletal mesh
       UClass* BicycleAnimation;
       USkeletalMesh* BicycleMesh;
    
       //Enum for parts that we want to control from simulink
       enum {
           BIKE_BODY = 0,
           FRONT_WHEEL = 1,
           REAR_WHEEL =2,
       };
    
   public:
       ABicycleActor();
    
       //Override functions for enabling Simulink to control this actor
       virtual void Sim3dInit() override;
       virtual void Sim3dSetup() override;
       virtual void Sim3dStep(float DeltaSeconds) override;
       virtual void Sim3dRelease() override;
   
    
       //Some helper functions
       void SetMesh(FString MeshRef);
       void SetAnim(FString AnimRef);
    
       //Function to update position/orientation of actor at each step
       virtual void Transform();
    
       // Returns Mesh subobject
       class USkeletalMeshComponent* GetMesh() const;
    
       //Reference to skeletal mesh component
       UPROPERTY(Category = Bicyclist,
           VisibleDefaultsOnly,
           BlueprintReadOnly,
           meta = (AllowPrivateAccess = "true"))
           class USkeletalMeshComponent* Mesh;
   
       static const int NumberOfParts = 3;
   
       int GetNumberOfParts() const override {
       return NumberOfParts;
       }
    
   };
    
   // Returns Mesh subobject
   FORCEINLINE USkeletalMeshComponent* ABicycleActor::GetMesh() const {
       return Mesh;
   }

    Code: BicycleActor.cpp

   // Copyright 2019-2021 The MathWorks, Inc.
   #include "BicycleActor.h"
   #include "SimulinkBikeAnimInst.h"
   #include "Sim3dActorTransform.h"
   #include "Math/UnrealMathUtility.h"
   
   ABicycleActor::ABicycleActor() {
   
   	//Create mesh component
   	Mesh = CreateOptionalDefaultSubobject<USkeletalMeshComponent>(TEXT("ABicycleMesh"));
   	RootComponent = Mesh;
   }
   
   void ABicycleActor::Sim3dInit() {
   	Super::Sim3dInit();
   }
   
   void ABicycleActor::Sim3dSetup() {
   	SetMesh(TEXT("/MathWorksSimulation/Vehicles/Bicyclist/Meshes/SK_Bicycle"));
   	SetAnim(TEXT("/MathWorksSimulation/Vehicles/Bicyclist/Meshes/BikeAnimation.BikeAnimation_C"));
   
   	GetMesh()->SetSkeletalMesh(BicycleMesh);
   	GetMesh()->SetAnimationMode(EAnimationMode::AnimationBlueprint);
   	GetMesh()->SetAnimInstanceClass(BicycleAnimation);
   	SetupTransform();
   	ReadTransform();
   	Transform();
   }
   
   void ABicycleActor::Sim3dStep(float DeltaTime) {
   	ReadTransform();
   	Transform();
   	WriteTransform();
   }
   
   void ABicycleActor::Sim3dRelease() {
   	Super::Sim3dRelease();
   }
   
   void ABicycleActor::Transform() {
   	//Initialize
   	int status = 0;
   	USimulinkBikeAnimInst* Animation = NULL;
   	Animation = Cast<USimulinkBikeAnimInst>(GetMesh()->GetAnimInstance());
   
   
   	//Set properies in animation blueprint
   	Animation->FWheelRotation = Sim3dActorTransform->GetPitch(FRONT_WHEEL);
   	Animation->RWheelRotation = Sim3dActorTransform->GetPitch(REAR_WHEEL);
   }
   
   void ABicycleActor::SetMesh(FString MeshPath) {
   	BicycleMesh =
   		Cast<USkeletalMesh>(StaticLoadObject(USkeletalMesh::StaticClass(), NULL, *MeshPath));
   }
   
   void ABicycleActor::SetAnim(FString AnimPath) {
   	BicycleAnimation = StaticLoadClass(USimulinkBikeAnimInst::StaticClass(), NULL, *AnimPath);
   }

   Tip

   In the code, make sure to use relative paths when you specify the mesh and animation asset locations.

   void ABicycleActor::Sim3dSetup() {
   	SetMesh(TEXT("/MathWorksSimulation/Vehicles/Bicyclist/Meshes/SK_Bicycle"));
   	SetAnim(TEXT("/MathWorksSimulation/Vehicles/Bicyclist/Meshes/BikeAnimation.BikeAnimation_C"));
   
   	GetMesh()->SetSkeletalMesh(BicycleMesh);
   	GetMesh()->SetAnimationMode(EAnimationMode::AnimationBlueprint);
   	GetMesh()->SetAnimInstanceClass(BicycleAnimation);
   	Transform();
   }

5. In Visual Studio, select Debug > Start Debugging or press F5 to run the solution. The Unreal Editor opens.

Step 6: Instantiate the Bicycle Actor

1. In your Simulink model, use the Simulation 3D Scene Configuration block Open Unreal Editor parameter to open the Unreal Editor.

2. Open the level HwStraight. Select File > Open Level and select HwStraight. Place the Bicycle Actor in the scene.

   

3. Set the tag to the same value as the Simulation 3D Actor Transform Set block Tag for actor in 3D scene, ActorTag. For this example, set the value to Bike1.

   

Set Up Camera View (Optional)

Optionally, set up a camera view to override the default view. You can use either use keyboard shortcuts and mouse actions to view and navigate in the 3D environment or a level blueprint to set up the camera view.

Step 7: Use Keyboard Shortcuts and Mouse Actions

To control the camera view use the keyboard shortcuts and mouse actions. For more information on the keyboard shortcuts and mouse actions, see Navigate in Unreal Engine Environment.

Step 8: Use Level Blueprint

To override the default camera view:

1. Add a camera actor. Assign it as a child of the BicycleActor.

2. Use the Transform settings to specify the location and viewing angle.

   

3. Open the level blueprint.

   

4. In the level blueprint, make these connections. If you right-click on the Event Graph to find nodes, clear Context Sensitive. If you have a CameraActor, you can drag it to the Event Graph from the World Outliner view in the editor.

   

5. Save the blueprint and project. Close the Unreal Editor.

Run Simulation

After you configure the Simulink model and Unreal Editor environment, run a simulation.

1. In your Simulink model, make sure that you have set the Simulation 3D Scene Configuration parameters to these values:

   • Scene source — Unreal Editor

   • Project — Name and location of the installed support package project file, for example, C:\Local\AutoVrtlEnv\AutoVrtlEnv.uproject.

   • Scene view — Scene Origin

2. Use the Simulation 3D Scene Configuration block Open Unreal Editor parameter to open the Unreal Editor.

3. Run the simulation.

   1. In the Simulink model, click Run.

      Because the source of the scenes is the project opened in the Unreal Editor, the simulation does not start.

   2. Verify that the Diagnostic Viewer window in Simulink displays this message:

      In the Simulation 3D Scene Configuration block, you set the scene source to 'Unreal Editor'. In Unreal Editor, select 'Play' to view the scene.

      This message confirms that Simulink has instantiated the actors and other assets in the Unreal Engine 3D environment.

   3. In the Unreal Editor, click Play. The simulation runs in the scene currently open in the Unreal Editor.