Overview of Chrono::Sensor

The Chrono::Sensor module provides support for simulating RGB cameras, lidar, GPS, and IMU within a Chrono simulation. Sensors are objects that are attached to Chrono Bodies(ChBody). Chrono::Sensor is currently compatible with the core rigid body simulation in Chrono including Chrono::Vehicle.

Detailed overview of Chrono::Sensor.

How the sensor system is setup (more examples can be found in the sensor demos)

import ..
// Chrono
ChSystemNSC mphysicalSystem
// ...
// Setup and initialize sensors and sensor system (manager and environment)
auto manager = chrono_types::make_shared<ChSensor>();
manager->scene->AddPointLight({x,y,z}, {intensity, intensity, intensity}, distance);
// Simulation loop
// update the sensor manager
// perform step of dynamics

Chrono::Sensor design considerations

Since dynamic chrono simulations typically have a higher update frequency than sensors (dynamics: order 1kHz; sensors: 10-100Hz), the sensor framework uses a separate thread to manage the data curation.

Chrono::Sensor can leverage multiple render threads each managing a separate GPU for simulating a group of sensors. This is particularly useful for scenarios with multiple agents and numerous sensors that operate at various update frequencies.

Each sensor has a filter graph which users can extend to customize the computation pipeline for modeling specific sensor attributes or configuring specific data formats.

How key frames are used

Keyframes are a used for generating time-dependent effects such as motion blur on a camera and scanning effects in a lidar. These keyframes are time-stamped transforms of objects in the dynamic scene. When using motion blur or scanning time on the camera or lidar, the number of keyframes that Chrono::Sensor should save must be set using the following which tells Chrono::Sensor the timestep the dynamics will be advanced at as well as the longest time window for which a sensor will be collecting data.

auto manager = chrono_types::make_shared<ChSensor>();
manager->SetKeyframeSizeFromTimeStep((float)step_size, .2f);

Loading sensor models from JSON Files

auto cam = Sensor::CreateFromJSON(
GetChronoDataFile("sensor/json/generic/Camera.json"), // path to json file
my_body, // body to which the sensor is attached
ChFrame<>({-5, 0, 0}, Q_from_AngZ(0))); // attachment pose for the sensor
// add camera to the manager

Reference Frames and Relative Attachment Positions

Each Chrono sensor defaults to Z-up, X-forwad, and Y-left to match a vehicle ISO reference frame. For an RGB camera, this means that the z-axis points vertically in the image plane, the y-axis points left in the image plane, and the x-axis points into the image plane. For lidar, the x-axis point along rays with zero vertical angle and zero horizontal angle

std::string GetChronoDataFile(const std::string &filename)
Obtain the complete path to the specified filename, given relative to the Chrono data directory (thre...
Definition: ChGlobal.cpp:95