How 3D Simulation for Vehicle Dynamics Blockset Works

The vehicle dynamics models run programmable maneuvers in a photorealistic 3D visualization environment. Vehicle Dynamics Blockset™ integrates the 3D simulation environment with Simulink^® so that you can query the world around the vehicle for virtually testing perception, control, and planning algorithms. The Vehicle Dynamics Blockset visualization environment uses the Unreal Engine^® by Epic Games^®.

Understanding how this simulation environment works can help you troubleshoot issues and customize your models.

Communication with 3D Simulation Environment

When you use Vehicle Dynamics Blockset to run your algorithms, Simulink co-simulates the algorithms in the visualization engine.

In the Simulink environment, Vehicle Dynamics Blockset:

Determines the next position of objects by using 3D visualization environment feedback and vehicle dynamics models.
Configures the 3D visualization environment, specifically:
- Ray tracing
- Scene capture cameras
- Initial object positions

In the visualization engine environment, Vehicle Dynamics Blockset positions the objects and uses ray tracing to query the environment.

The diagram summarizes the communication between Simulink and the visualization engine.

Bidirectional information shared between Simulink and visualization engine

Block Execution Order

During simulation, the 3D simulation blocks follow a specific execution order:

The vehicle blocks initialize the vehicles and send their X, Y, and Yaw signal data to the Simulation 3D Scene Configuration block.
The Simulation 3D Scene Configuration block receives the vehicle data and sends it to the sensor blocks.
The sensor blocks receive the vehicle data and use it to accurately locate and visualize the vehicles.

The Priority property of the blocks controls this execution order. To access this property for any block, right-click the block, select Properties, and click the General tab. By default, Simulation 3D Vehicle with Ground Following blocks have a priority of -1, Simulation 3D Scene Configuration blocks have a priority of 0, and sensor blocks have a priority of 1.

If your sensors are not detecting vehicles in the scene, it is possible that the 3D simulation blocks are executing out of order. Try updating the execution order and simulating again. For more details on execution order, see Control and Display Execution Order.

Also be sure that all 3D simulation blocks are located in the same subsystem. Even if the blocks have the correct Priority settings, if they are located in different subsystems, they still might execute out of order.