Python Examples

monoDrive Python Examples

The monoDrive Python Client comes with several examples for connecting to and using the the monoDrive Simulator and Scenario Editor. The examples in the examples directory have many common elements that are discussed here.

Connecting to the Simulator

To connect to the monoDrive Simulator, construct a Simulator object:

simulator = Simulator.from_file(
    "examples/configurations/simulator_closed_loop.json",
    trajectory="examples/trajectories/Closed_Loop.json",
    sensors="examples/configurations/all_sensors.json",
    weather="examples/configurations/weather.json",
    ego="examples/configurations/vehicle.json"
)

simulator.start()

Here the simulator is being created from several of the provided configuration files for "Closed Loop" control of the ego vehicle.

Subscribing to Sensors

Once the client is connected to the simulator object, sensors can be configured and a callback function is connected to their output:

simulator.subscribe_to_sensor('Camera_8000', camera_on_update)

Here, Camera_8000 defines the unique identifier for the sensor which is a combination of the type field in all_sensors.json (i.e. Camera) and the desired port number for the data (i.e. 8000).

The callback function receives a packet of parsed camera data for use in perception algorithms. The callback can be as simple as:

def camera_on_update(frame: CameraFrame):
    """
    callback to process parsed camera data
    """
    camera_frame = frame
    # Process the frame of camera data

Sending Control Commands

In order to send vehicle controls to the simulator object for moving the EGO vehicle:

forward = 1
right = 0
brake = 0
drive_mode = 1
simulator.send_control(forward, right, brake, drive_mode)

Here the forward, right, and brake values are floating point numbers between -1.0 and 1.0 to control the vehicle's movement. The drive_mode is set to 1 for closed loop control. Typically applications would want to control the vehicle in a continuous loop while simulating.

Stopping the Simulator

When the application is complete, the simulator connection can be stopped:

simulator.stop()

Camera Annotation

The example code in the examples/camera_annotation.py demonstrates how to connect to an instance of the monoDrive Simulator and:

• Initiate "Replay" mode
• Subscribe to a Camera sensor's output and process the annotations in the frame provided by the simulation
• Subscribe to a Semantic Camera sensor's output and display the camera data

Here, the simulation is being "stepped" in Replay mode instead of direct control by providing a trajectory file and calling:

simulator.step()

on each iteration of the simulation.

The following code demonstrates how to utilize the annotation member of the Camera sensor:

if camera_frame:
    img = np.array(camera_frame.image[..., ::-1])
    for actor_annotation in camera_frame.annotation:
        for primitive_annotation in actor_annotation["2d_bounding_boxes"]:
            box = primitive_annotation["2d_bounding_box"]
            top_left = (int(box[0]), int(box[2]))
            bottom_right = (int(box[1]), int(box[3]))
            cv2.rectangle(img, top_left, bottom_right, (255, 0, 0), 2)

Closed Loop Example

The example in examples/closed_loop.py demonstrates how to connect to an instance of the monoDrive Simulator and:

• Control the ego vehicle directly
• Subscribe to several different sensors and define their callbacks
• Process and display Camera sensor data
• Process and display LiDAR sensor data

Connecting to and controlling a vehicle in Closed Loop mode is demonstrated in the above descriptions. Processing and displaying Camera sensor data can be done like:

if camera_frame:
    im = np.squeeze(camera_frame.image[..., ::-1])
    if data_camera is None:
        data_camera = ax_camera.imshow(im)
    else:
        data_camera.set_data(im)

Processing and displaying LiDAR sensor data can be done like:

if lidar_frame:
    data = np.array([[pt.x, pt.y, pt.z, pt.intensity] for pt in lidar_frame.points])
    data = data[np.any(data != 0, axis=1)]
    if data_lidar is None:
        data_lidar = ax_lidar.scatter(
        data[:, 0], data[:, 1], data[:, 2],
        s=0.1
        )
    else:
        data_lidar._offsets3d = (data[:, 0], data[:, 1], data[:, 2])

Replay Step Example

The example in examples/replay_step.py demonstrates how to connect to an instance of the monoDrive Simulator and:

• Initiate "Replay" mode and step the simulation
• Subscribe to a Camera sensor's output and display it
• Subscribe to a LiDAR sensor's output and display it

This example is very similar to the camera_annotation.py example.