Implementation:CARLA simulator Carla World Spawn Actor Attached

Knowledge Sources	CARLA Simulator CARLA Documentation
Domains	Autonomous Driving Simulation, Robotics Perception
Last Updated	2026-02-15 00:00 GMT

Overview

Concrete tool for spawning a sensor actor attached to a parent vehicle or actor provided by the CARLA simulator.

Description

The World.spawn_actor method, when called with the attach_to parameter, creates a new actor and immediately establishes a parent-child attachment. The transform parameter is interpreted as a relative offset from the parent actor's local coordinate frame, defining the sensor's mounting position and orientation.

This is the standard method for instrumenting vehicles with sensors. The spawned sensor actor automatically moves with its parent, and its world-space position is computed by composing the parent's transform with the relative offset. The attachment_type parameter controls the mechanical coupling between parent and child (Rigid for fixed mounting, SpringArm for damped following).

Unlike try_spawn_actor, this method raises a RuntimeError if the spawn fails, making it appropriate for critical sensor attachments where failure should halt execution.

Usage

Use this method to attach sensors (cameras, LiDAR, radar, GNSS, IMU) to vehicles. Call it after spawning the parent vehicle and configuring the sensor blueprint. Always register a listen callback on the spawned sensor to receive data.

Code Reference

Source Location

• Repository: CARLA
• File: LibCarla/source/carla/client/World.cpp
• Lines: L122-128
• Python binding: PythonAPI/carla/src/Sensor.cpp
• Lines: L22-40

Signature

World.spawn_actor(
    blueprint: carla.ActorBlueprint,
    transform: carla.Transform,
    attach_to: carla.Actor,
    attachment_type: carla.AttachmentType = carla.AttachmentType.Rigid
) -> carla.Sensor

Import

import carla

I/O Contract

Inputs

Name	Type	Required	Description
blueprint	carla.ActorBlueprint	Yes	The sensor blueprint with configured attributes (resolution, field of view, channels, etc.)
transform	carla.Transform	Yes	Relative transform from the parent actor's local frame, defining the sensor mounting position and orientation
attach_to	carla.Actor	Yes	The parent actor (typically a vehicle) to which the sensor will be attached
attachment_type	carla.AttachmentType	No	Attachment mode: Rigid (fixed, default), SpringArm (damped following), or SpringArmGhost (damped, no collision). Defaults to Rigid.

Outputs

Name	Type	Description
return	carla.Sensor	The spawned sensor actor, attached to the parent. Call .listen(callback) to receive sensor data.

Usage Examples

Basic Example

import carla
import numpy as np

client = carla.Client("localhost", 2000)
client.set_timeout(10.0)
world = client.get_world()

# Spawn ego vehicle
blueprint_library = world.get_blueprint_library()
vehicle_bp = blueprint_library.find("vehicle.tesla.model3")
spawn_point = world.get_map().get_spawn_points()[0]
ego_vehicle = world.spawn_actor(vehicle_bp, spawn_point)

# Configure an RGB camera
camera_bp = blueprint_library.find("sensor.camera.rgb")
camera_bp.set_attribute("image_size_x", "1920")
camera_bp.set_attribute("image_size_y", "1080")
camera_bp.set_attribute("fov", "90")

# Attach camera to the vehicle roof (relative transform)
camera_transform = carla.Transform(
    carla.Location(x=1.5, y=0.0, z=2.4),
    carla.Rotation(pitch=-15.0, yaw=0.0, roll=0.0)
)
camera_sensor = world.spawn_actor(
    camera_bp,
    camera_transform,
    attach_to=ego_vehicle,
    attachment_type=carla.AttachmentType.Rigid
)

# Register callback to process camera data
def process_image(image):
    array = np.frombuffer(image.raw_data, dtype=np.uint8)
    array = array.reshape((image.height, image.width, 4))  # BGRA
    print(f"Frame {image.frame}: captured {image.width}x{image.height} image")

camera_sensor.listen(process_image)

Full Sensor Suite Example

import carla

client = carla.Client("localhost", 2000)
client.set_timeout(10.0)
world = client.get_world()

blueprint_library = world.get_blueprint_library()

# Spawn ego vehicle
vehicle_bp = blueprint_library.find("vehicle.lincoln.mkz_2020")
spawn_point = world.get_map().get_spawn_points()[0]
ego_vehicle = world.spawn_actor(vehicle_bp, spawn_point)

sensors = []

# Front RGB camera
cam_bp = blueprint_library.find("sensor.camera.rgb")
cam_bp.set_attribute("image_size_x", "1280")
cam_bp.set_attribute("image_size_y", "720")
cam_transform = carla.Transform(carla.Location(x=2.0, z=1.4))
front_camera = world.spawn_actor(cam_bp, cam_transform, attach_to=ego_vehicle)
front_camera.listen(lambda img: img.save_to_disk(f"output/front/{img.frame:06d}.png"))
sensors.append(front_camera)

# Roof LiDAR
lidar_bp = blueprint_library.find("sensor.lidar.ray_cast")
lidar_bp.set_attribute("channels", "64")
lidar_bp.set_attribute("points_per_second", "1200000")
lidar_bp.set_attribute("range", "100.0")
lidar_transform = carla.Transform(carla.Location(x=0.0, z=2.4))
lidar_sensor = world.spawn_actor(lidar_bp, lidar_transform, attach_to=ego_vehicle)
lidar_sensor.listen(lambda data: data.save_to_disk(f"output/lidar/{data.frame:06d}.ply"))
sensors.append(lidar_sensor)

# Front radar
radar_bp = blueprint_library.find("sensor.other.radar")
radar_bp.set_attribute("horizontal_fov", "30.0")
radar_bp.set_attribute("vertical_fov", "10.0")
radar_transform = carla.Transform(carla.Location(x=2.2, z=0.5))
radar_sensor = world.spawn_actor(radar_bp, radar_transform, attach_to=ego_vehicle)
radar_sensor.listen(lambda data: print(f"Radar detections: {len(data)}"))
sensors.append(radar_sensor)

# GNSS sensor
gnss_bp = blueprint_library.find("sensor.other.gnss")
gnss_transform = carla.Transform(carla.Location(z=2.4))
gnss_sensor = world.spawn_actor(gnss_bp, gnss_transform, attach_to=ego_vehicle)
gnss_sensor.listen(lambda data: print(f"GPS: lat={data.latitude:.6f}, lon={data.longitude:.6f}"))
sensors.append(gnss_sensor)

# IMU sensor
imu_bp = blueprint_library.find("sensor.other.imu")
imu_transform = carla.Transform()  # Vehicle center
imu_sensor = world.spawn_actor(imu_bp, imu_transform, attach_to=ego_vehicle)
imu_sensor.listen(lambda data: print(f"IMU: accel=({data.accelerometer.x:.2f}, {data.accelerometer.y:.2f}, {data.accelerometer.z:.2f})"))
sensors.append(imu_sensor)

# Cleanup
# for sensor in sensors:
#     sensor.stop()
#     sensor.destroy()
# ego_vehicle.destroy()

Related Pages

Implements Principle

• Principle:CARLA_simulator_Carla_Sensor_Attachment