Customize Unreal Engine Scenes Using Simulink and Unreal Editor

Step 3 of 4 in Customize Unreal Engine Scenes for UAVs

After you install the UAV Toolbox Interface for Unreal Engine^® Projects support package as described in Install Support Package for Customizing Scenes, you can simulate in custom scenes simultaneously from both the Unreal^® Editor and Simulink^®. By using this co-simulation framework, you can add vehicles and sensors to a Simulink model and then run this simulation in your custom scene.

To use a project that you developed using a prior release of the support package, first migrate the project to be compatible with the currently supported Unreal Engine version. See Migrate Projects Developed Using Prior Support Packages.

Open Unreal Editor from Simulink

If you open the Unreal Editor from outside of MATLAB^® or Simulink, then Simulink fails to establish a connection with the editor. To establish this connection, you must open your project from a Simulink model.

Open a Simulink model configured to simulate in the 3D environment. At a minimum, the model must contain a Simulation 3D Scene Configuration block. For example, open a simple model that simulates a UAV flying in a US city block. This model here is the photo-realistic simulation variant from the UAV Package Delivery example.
In the Simulation 3D Scene Configuration block of this model, set the Scene source parameter to Unreal Editor.
In the Project parameter, browse for the project file that contains the scenes that you want to customize.
For example, this sample path specifies the AutoVrtlEnv project that comes installed with the UAV Toolbox Interface for Unreal Engine Projects support package.
```
C:\project\AutoVrtlEnv\AutoVrtlEnv.uproject
```
This sample path specifies a custom project.
```
Z:\UnrealProjects\myProject\myProject.uproject
```
Click Open Unreal Editor. The Unreal Editor opens and loads a scene from your project.

The first time that you open the Unreal Editor from Simulink, you might be asked to rebuild UE4Editor DLL files or the AutoVrtlEnv module. Click Yes to rebuild these files or modules. The editor also prompts you that new plugins are available. Click Manage Plugins and verify that the MathWorks Interface and MathWorks UAV Content plugins are installed. Make sure both plugins are enabled by verifying that the Enabled box is checked for both. These plugins are the MathWorksSimulation.uplugin and MathworksUAVContent.uplugin files that you copied into your Unreal Editor installation in Install Support Package for Customizing Scenes. After enabling the plugins, you may have to restart the Unreal Editor. Click Restart Now if prompted.

Messages about files with the name '_BuiltData' indicate missing lighting data for the associated level. Before shipping an executable, rebuild the level lighting.

If you receive a warning that the lighting needs to be rebuilt, from the toolbar above the editor window, select Build > Build Lighting Only. The editor issues this warning the first time you open a scene or when you add new elements to a scene. To use the lighting that comes installed with AutoVrtlEnv, see Use AutoVrtlEnv Project Lighting in Custom Scene.

Reparent Actor Blueprint

Note

If you are using a scene from the AutoVrtlEnv project that comes installed with the UAV Toolbox Interface for Unreal Engine Projects support package, skip this section. However, if you create a new scene based off of one of the scenes in this project, then you must complete this section.

The first time that you open a custom scene from Simulink, you need to associate, or reparent, this project with the Sim3dLevelScriptActor level blueprint used in UAV Toolbox. The level blueprint controls how objects interact with the Unreal Engine environment once they are placed in it. Simulink returns an error at the start of simulation if the project is not reparented. You must reparent each scene in a custom project separately.

To reparent the level blueprint, follow these steps:

In the Unreal Editor toolbar, select Blueprints > Open Level Blueprint.
In the Level Blueprint window, select File > Reparent Blueprint.
Click the Sim3dLevelScriptActor blueprint. If you do not see the Sim3dLevelScriptActor blueprint listed, use these steps to check that you have the MathWorksSimulation 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.
  If you do not see the MathWorks Interface plugin in this window, repeat the steps under Install Support Package for Customizing Scenes and reopen the editor from Simulink.
3. Close the editor and reopen it from Simulink.
Close the Level Blueprint window.

You can also reparent the level script actor class for a custom project. To set the default class, from the Unreal Editor toolbar, select Edit > Project Settings > Engine > General Settings. Select Sim3dLevelScriptActor as the default class for the level script actor class. Close Project Settings to save the default values and reopen the editor from Simulink.

Unreal Editor Engine in Project Settings

To use the default controls and features that come with the Mathworks Interface plugin in a custom project, you must set the default game mode of the project. In the Unreal Editor toolbar, select Edit > Project Settings > Project > Maps & Modes. Select Sim3dGameMode as the default game mode. Close Project Settings to save the default values and reopen the editor from Simulink.

Unreal Editor Project in Project Settings

Create or Modify Scenes in Unreal Editor

After you open the editor from Simulink, you can modify the scenes in your project or create new scenes.

Open Scene

In the Unreal Editor, scenes within a project are referred to as levels. Levels come in several types, and scenes have a level type of map.

To open a prebuilt scene from the AutoVrtlEnv.uproject file, in the Content Drawer pane below the editor window, navigate to the Content > Maps folder. Then, select the map that corresponds to the scene you want to modify.

Unreal Editor Map	UAV Toolbox Scene
`USCityBlock`	US City Block
`Suburban`	Suburban

To open a scene within your own project, in the Content Drawer pane, navigate to the folder that contains your scenes.

Create New Scene

To create a new scene in your project, from the top-left menu of the editor, select File > New Level.

Alternatively, you can create a new scene from an existing one. This technique is useful if you want to use one of the prebuilt scenes in the AutoVrtlEnv project as a starting point for creating your own scene. To save a version of the currently opened scene to your project, from the top-left menu of the editor, select File > Save Current As. The new scene is saved to the same location as the existing scene.

Add Assets to Scene

In the Unreal Editor, elements within a scene are referred to as assets. To add assets to a scene, you can browse or search for them in the Content Browser pane at the bottom and drag them into the editor window.

When adding assets to a scene that is in the AutoVrtlEnv project, you can choose from a library of driving-related assets. These assets are built as static meshes and begin with the prefix SM_. Search for these objects in the Content Drawer pane.

For example, add a stop sign to a scene in the AutoVrtlEnv project.

In the Content Drawer pane at the bottom of the editor, navigate to the Content folder.
In the search bar, search for SM_StopSign. Drag the stop sign from the Content Drawer into the editing window. You can then change the position of the stop sign in the editing window or on the Details pane on the right, in the Transform section.

If you want to override the default weather or use enhanced fog conditions in the scene, add the Exponential Height Fog actor.

Exponential Height Fog actor selection

The Unreal Editor uses a left-hand Z-up coordinate system, where the Y-axis points to the right. UAV Toolbox uses a right-hand Z-down coordinate system, where the Y-axis points to the left. When positioning objects in a scene, keep this coordinate system difference in mind. In the two coordinate systems, the positive and negative signs for the Y-axis and pitch angle values are reversed.

For more information on modifying scenes and adding assets, see Unreal Engine 5.3 Documentation.

To migrate assets from the AutoVrtlEnv project into your own project file, see the Unreal Engine documentation.

To obtain semantic segmentation data from a scene, then you must apply stencil IDs to the objects added to a scene. For more information, see Apply Semantic Segmentation Labels to Custom Scenes.

Use `AutoVrtlEnv` Project Lighting in Custom Scene

To use the lighting that comes installed with the AutoVrtlEnv project in UAV Toolbox, follow these steps.

On the World Settings tab, clear Force no precomputed lighting.
Under Build, select Lighting Quality > Production to rebuild the maps with production quality. Rebuilding large maps can take time.

Run Simulation

Verify that the Simulink model and Unreal Editor are configured to co-simulate by running a test simulation.

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. Instead, you must start the simulation from the editor.
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 vehicles and other objects in the Unreal Engine 3D environment.
In the Unreal Editor, click Play. The simulation runs in the scene currently open in the Unreal Editor.
- If your Simulink model contains vehicles, these vehicles drive through the scene that is open in the editor.
- If your Simulink model includes sensors, these sensors capture data from the scene that is open in the editor.

To control the view of the scene during simulation, in the Simulation 3D Scene Configuration block, select the vehicle name from the Scene view parameter. To change the scene view as the simulation runs, use the numeric keypad in the editor. The table shows the position of the camera displaying the scene, relative to the vehicle selected in the Scene view parameter.

Key	Camera View
1	Back left
2	Back
3	Back right
4	Left
5	Internal
6	Right
7	Front left
8	Front
9	Front right
0	Overhead

To restart a simulation, click Run in the Simulink model, wait until the Diagnostic Viewer displays the confirmation message, and then click Play in the editor. If you click Play before starting the simulation in your model, the connection between Simulink and the Unreal Editor is not established, and the editor displays an empty scene.

After tuning your custom scene based on simulation results, you can then package the scene into an executable. For more details, see Package Custom Scenes into Executable.