Collision detection and distances

Python

from pathlib import Path
 
import pinocchio as pin
 
pinocchio_model_dir = Path(__file__).parent.parent / "models"
 
model_path = pinocchio_model_dir / "example-robot-data/robots"
mesh_dir = pinocchio_model_dir
urdf_filename = "romeo_small.urdf"
urdf_model_path = model_path / "romeo_description/urdf" / urdf_filename
 
# Load model
model = pin.buildModelFromUrdf(urdf_model_path, pin.JointModelFreeFlyer())
 
# Load collision geometries
geom_model = pin.buildGeomFromUrdf(
    model, urdf_model_path, pin.GeometryType.COLLISION, mesh_dir
)
 
# Add collisition pairs
geom_model.addAllCollisionPairs()
print("num collision pairs - initial:", len(geom_model.collisionPairs))
 
# Remove collision pairs listed in the SRDF file
srdf_filename = "romeo.srdf"
srdf_model_path = model_path / "romeo_description/srdf" / srdf_filename
 
pin.removeCollisionPairs(model, geom_model, srdf_model_path)
print(
    "num collision pairs - after removing useless collision pairs:",
    len(geom_model.collisionPairs),
)
 
# Load reference configuration
pin.loadReferenceConfigurations(model, srdf_model_path)
 
# Retrieve the half sitting position from the SRDF file
q = model.referenceConfigurations["half_sitting"]
 
# Create data structures
data = model.createData()
geom_data = pin.GeometryData(geom_model)
 
 
# Compute all the collisions
pin.computeCollisions(model, data, geom_model, geom_data, q, False)
 
# Print the status of collision for all collision pairs
for k in range(len(geom_model.collisionPairs)):
    cr = geom_data.collisionResults[k]
    cp = geom_model.collisionPairs[k]
    print(
        "collision pair:",
        cp.first,
        ",",
        cp.second,
        "- collision:",
        "Yes" if cr.isCollision() else "No",
    )
 
# Compute for a single pair of collision
pin.updateGeometryPlacements(model, data, geom_model, geom_data, q)
pin.computeCollision(geom_model, geom_data, 0)

C++

#include "pinocchio/parsers/urdf.hpp"
#include "pinocchio/parsers/srdf.hpp"
 
#include "pinocchio/algorithm/joint-configuration.hpp"
#include "pinocchio/algorithm/geometry.hpp"
#include "pinocchio/collision/collision.hpp"
 
#include <iostream>
 
// PINOCCHIO_MODEL_DIR is defined by the CMake but you can define your own modeldirectory here.
#ifndef PINOCCHIO_MODEL_DIR
  #define PINOCCHIO_MODEL_DIR "path_to_the_model_dir"
#endif
 
int main(int /*argc*/, char ** /*argv*/)
{
  using namespace pinocchio;
  const std::string robots_model_path = PINOCCHIO_MODEL_DIR;
 
  // You should change here to set up your own URDF file
  const std::string urdf_filename =
    robots_model_path
    + std::string("/example-robot-data/robots/talos_data/robots/talos_reduced.urdf");
  // You should change here to set up your own SRDF file
  const std::string srdf_filename =
    robots_model_path + std::string("/example-robot-data/robots/talos_data/srdf/talos.srdf");
 
  // Load the URDF model contained in urdf_filename
  Model model;
  pinocchio::urdf::buildModel(urdf_filename, model);
 
  // Build the data associated to the model
  Data data(model);
 
  // Load the geometries associated to model which are contained in the URDF file
  GeometryModel geom_model;
  pinocchio::urdf::buildGeom(
    model, urdf_filename, pinocchio::COLLISION, geom_model, robots_model_path);
 
  // Add all possible collision pairs and remove the ones collected in the SRDF file
  geom_model.addAllCollisionPairs();
  pinocchio::srdf::removeCollisionPairs(model, geom_model, srdf_filename);
 
  // Build the data associated to the geom_model
  GeometryData geom_data(geom_model); // contained the intermediate computations, like the placement
                                      // of all the geometries with respect to the world frame
 
  // Load the reference configuration of the robots (this one should be collision free)
  pinocchio::srdf::loadReferenceConfigurations(
    model,
    srdf_filename); // the reference configuratio stored in the SRDF file is called half_sitting
 
  const Model::ConfigVectorType & q = model.referenceConfigurations["half_sitting"];
 
  // And test all the collision pairs
  computeCollisions(model, data, geom_model, geom_data, q);
 
  // Print the status of all the collision pairs
  for (size_t k = 0; k < geom_model.collisionPairs.size(); ++k)
  {
    const CollisionPair & cp = geom_model.collisionPairs[k];
    const hpp::fcl::CollisionResult & cr = geom_data.collisionResults[k];
 
    std::cout << "collision pair: " << cp.first << " , " << cp.second << " - collision: ";
    std::cout << (cr.isCollision() ? "yes" : "no") << std::endl;
  }
 
  // If you want to stop as soon as a collision is encounter, just add false for the final default
  // argument stopAtFirstCollision
  computeCollisions(model, data, geom_model, geom_data, q, true);
 
  // And if you to check only one collision pair, e.g. the third one, at the neutral element of the
  // Configuration Space of the robot
  const PairIndex pair_id = 2;
  const Model::ConfigVectorType q_neutral = neutral(model);
  updateGeometryPlacements(
    model, data, geom_model, geom_data,
    q_neutral); // performs a forward kinematics over the whole kinematics model + update the
                // placement of all the geometries contained inside geom_model
  computeCollision(geom_model, geom_data, pair_id);
 
  return 0;
}