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
while(){
 
  // update the sensor manager
  manager->Update();
 
  // perform step of dynamics
  mphysicalSystem.DoStepDynamics(step_size);
}

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
  manager->AddSensor(cam);

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