MRPT Graph Slam Minimal Example - c++

Question

I am trying to come up with a "minimal" way of running a graph slam application using MRPT. The sensor data (LaserScan / Odometry) will be provided by a custom middleware similiar to ROS. After reading docs and source codes (both for the MRPT and the ROS bridge) extensively, I came up with the following snippet:
std::string config_file = "../../../laser_odometry.ini";
std::string rawlog_fname = "";
std::string fname_GT = "";
auto node_reg = mrpt::graphslam::deciders::CICPCriteriaNRD<mrpt::graphs::CNetworkOfPoses2DInf>{};
auto edge_reg = mrpt::graphslam::deciders::CICPCriteriaERD<mrpt::graphs::CNetworkOfPoses2DInf>{};
auto optimizer = mrpt::graphslam::optimizers::CLevMarqGSO<mrpt::graphs::CNetworkOfPoses2DInf>{};
auto win3d = mrpt::gui::CDisplayWindow3D{"Slam", 800, 600};
auto win_observer = mrpt::graphslam::CWindowObserver{};
auto win_manager = mrpt::graphslam::CWindowManager{&win3d, &win_observer};
auto engine = mrpt::graphslam::CGraphSlamEngine<mrpt::graphs::CNetworkOfPoses2DInf>{
config_file, rawlog_fname, fname_GT, &win_manager, &node_reg, &edge_reg, &optimizer};
for (size_t measurement_count = 0;;) {
// grab laser scan from the network, then fill it (hardcoded values for now), e.g:
auto scan_ptr = mrpt::obs::CObservation2DRangeScan::Create();
scan_ptr->timestamp = std::chrono::system_clock::now().time_since_epoch().count();
scan_ptr->rightToLeft = true;
scan_ptr->sensorLabel = "";
scan_ptr->aperture = 3.14; // rad (max-min)
scan_ptr->maxRange = 3.0; // m
scan_ptr->sensorPose = mrpt::poses::CPose3D{};
scan_ptr->resizeScan(30);
for (int i = 0; i < 30; ++i) {
scan_ptr->setScanRange(i, 0.5);
scan_ptr->setScanRangeValidity(i, true);
}
{ // Send LaserScan measurement to the slam engine
auto obs_ptr = std::dynamic_pointer_cast<mrpt::obs::CObservation>(scan_ptr);
engine.execGraphSlamStep(obs_ptr, measurement_count);
++measurement_count;
}
// grab odometry from the network, then fill it (hardcoded values for now), e.g:
auto odometry_ptr = mrpt::obs::CObservationOdometry::Create();
odometry_ptr->timestamp = std::chrono::system_clock::now().time_since_epoch().count();
odometry_ptr->hasVelocities = false;
odometry_ptr->odometry.x(0);
odometry_ptr->odometry.y(0);
odometry_ptr->odometry.phi(0);
{ // Send Odometry measurement to the slam engine
auto obs_ptr = std::dynamic_pointer_cast<mrpt::obs::CObservation>(odometry_ptr);
engine.execGraphSlamStep(obs_ptr, measurement_count);
++measurement_count;
}
// Get pose estimation from the engine
auto pose = engine.getCurrentRobotPosEstimation();
}
Am I in the right direction here? Did I miss something?

Answer 1

Hmm, at a first look the script seems fine, you are providing odometry and the laser scan in two different steps and in Observation form.
Minor note
auto node_reg = mrpt::graphslam::deciders::CICPCriteriaNRD{};
If you want to run with Odometry + laser scans use CFixedIntervalsNRD instead. It's much better tested and actually makes use of those measurements.
There is no minimal graphslam-engine example at present in MRPT but here's here's the main method for running graph-slam with datasets:
https://github.com/MRPT/mrpt/blob/26ee0f2d3a9366c50faa5f78d0388476ae886808/libs/graphslam/include/mrpt/graphslam/apps_related/CGraphSlamHandler_impl.h#L395
template <class GRAPH_T>
void CGraphSlamHandler<GRAPH_T>::execute()
{
using namespace mrpt::obs;
ASSERTDEB_(m_engine);
// Variables initialization
mrpt::io::CFileGZInputStream rawlog_stream(m_rawlog_fname);
CActionCollection::Ptr action;
CSensoryFrame::Ptr observations;
CObservation::Ptr observation;
size_t curr_rawlog_entry;
auto arch = mrpt::serialization::archiveFrom(rawlog_stream);
// Read the dataset and pass the measurements to CGraphSlamEngine
bool cont_exec = true;
while (CRawlog::getActionObservationPairOrObservation(
arch, action, observations, observation, curr_rawlog_entry) &&
cont_exec)
{
// actual call to the graphSLAM execution method
// Exit if user pressed C-c
cont_exec = m_engine->_execGraphSlamStep(
action, observations, observation, curr_rawlog_entry);
}
m_logger->logFmt(mrpt::system::LVL_WARN, "Finished graphslam execution.");
}
You basically grab the data and then continuously feed them to CGraphSlamEngine via either execGraphSlamStep or _execGraphSlamStep methods.
Here's also the relevant snippet for processing measurements in the corresponding ROS wrapper that operates with measurements from ROS topics:
https://github.com/mrpt-ros-pkg/mrpt_slam/blob/8b32136e2a381b1759eb12458b4adba65e2335da/mrpt_graphslam_2d/include/mrpt_graphslam_2d/CGraphSlamHandler_ROS_impl.h#L719
template<class GRAPH_T>
void CGraphSlamHandler_ROS<GRAPH_T>::processObservation(
mrpt::obs::CObservation::Ptr& observ) {
this->_process(observ);
}
template<class GRAPH_T>
void CGraphSlamHandler_ROS<GRAPH_T>::_process(
mrpt::obs::CObservation::Ptr& observ) {
using namespace mrpt::utils;
if (!this->m_engine->isPaused()) {
this->m_engine->execGraphSlamStep(observ, m_measurement_cnt);
m_measurement_cnt++;
}
}