Animate Custom Actors in the Unreal Editor

This example uses:

Simulink 3D Animation Simulink 3D Animation

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.

Simulink model with connected blocks

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

In your Simulink model, use the Simulation 3D Scene Configuration block Open Unreal Editor parameter to open the Unreal Editor.
Select Tools > New C++ Class. In the Choose Parent Class dialog box, select All Classes. Search for AnimInst. Select the AnimInstance and click Next.
Name the new C++ class SimulinkBikeAnimInst. Select Public. Click Create Class.

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

Visual studio solution explorer

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

Code: SimulinkBikeAnimInst.cpp

In the Unreal Editor click Compile.

Step 4: Create Animation Blueprint

In the Unreal Editor, on the Content Browser tab, under View Options, select Show Engine Content and Show Plugin Content.
Add the animation mesh. On the Content Browser tab, navigate to MathWorksAutomotiveContent Content > Vehicles > Bicyclist > Meshes.
Right-click Meshes and select Add/Import Content > Animation > Animation Blueprint.
In the Create Animation Blueprint dialog box, select:
- Parent Class: SimulinkBikeAnimInst
- Target Skeleton: SK_Bicycle_Skeleton
Click Create.
Name the blueprint BikeAnimation. Right-click and select Save.
Double-click 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
Compile and save the blueprint.

Step 5: Create Bicycle Actor C++ Class

In the Unreal Editor, on the Content Browser tab, under View Options, select Show Engine Content and Show Plugin Content.
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.
Name the new Sim3dActor BicycleActor. Select Public. Click Create Class.

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

Visual studio solution explorer

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

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("/MathWorksAutomotiveContent/Vehicles/Bicyclist/Meshes/SK_Bicycle"));
	SetAnim(TEXT("/MathWorksAutomotiveContent/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("/MathWorksAutomotiveContent/Vehicles/Bicyclist/Meshes/SK_Bicycle"));
	SetAnim(TEXT("/MathWorksAutomotiveContent/Vehicles/Bicyclist/Meshes/BikeAnimation.BikeAnimation_C"));

	GetMesh()->SetSkeletalMesh(BicycleMesh);
	GetMesh()->SetAnimationMode(EAnimationMode::AnimationBlueprint);
	GetMesh()->SetAnimInstanceClass(BicycleAnimation);
	Transform();
}

In the Unreal Editor click Compile.

Step 6: Instantiate the Bicycle Actor

In your Simulink model, use the Simulation 3D Scene Configuration block Open Unreal Editor parameter to open the Unreal Editor.
Open the level HwStraight. Select File > Open Level and select HwStraight. Place the Bicycle Actor in the scene.
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 Simulink or a level blueprint to set up the camera view. For the recommended option, use Simulink.

Step 7: Use Simulink (Recommended)

To setup a camera view that follows along with the bicycle:

Add these blocks to the model.
- One Ramp block
- One Add block
- Three Constant blocks
- Simulation 3D Actor Transform Set block
Connect and name the blocks as shown.

Set these block parameters.

Block	Parameter Settings
Simulation 3D Actor Transform Set: Camera Control	Tag for actor in 3D scene, ActorTag — `MainCamera1`
CamTranslation	Constant value — `[0 -5.1 0.56]` Interpret vector parameters as 1-D — `off`
CamRotation	Constant value — `[0 0 deg2rad(85)]` Interpret vector parameters as 1-D — `off`
CamScale	Constant value — `[1 1 1]` Interpret vector parameters as 1-D — `off`

Step 7: Use Level Blueprint

To override the default camera view:

Add a camera actor. Assign it as a child of the BicycleActor.
Use the Transform settings to specify the location and viewing angle.
Open the level blueprint.
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.
Save the blueprint and project. Close the Unreal Editor.

Run Simulation

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

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