Scenarios

Override init_world (C++, Python) with the logic to initialize a world: create/modify/delete entities, set termination criteria, set the bounding box, setup a lattice, …). If you need to sample from random distribution, use the provided random generator (C++, Python), that will guarantee that the world initialization will be deterministic.

Virtual methods

C++ method	Python method	override
init_world	init_world	should

Class skeleton

C++Python

#include "navground/sim/scenario.h"

namespace sim = navground::sim;

struct MyScenario : public sim::Scenario {
  // SHOULD override
  // add here the logic to initialize the world
  void init_world(sim::World *world, seed = std::nullopt) override {
    // call the super class: when the scenario is configured thought YAML, 
    // it will add agents and obstacles as specified in the configuration.
    sim::Scenario::init_world(world, seed);
    // use the world random generator to sample random variable. 
    auto & rng = world->get_random_generator();
    // manipulate the world: create/add/modify/delete agents and obstacles
  }
};

Groups

Another way to customize a scenario, without subclassing, is to add a group of agent, i.e., a sub-class of Group (C++, Python), that has a virtual method add_to_world

C++ method	Python method	override
add_to_world	add_to_world	must

which should spawn the group to the world, but is not restricted to that. if required, define a new type of group

C++Python

#include "navground/sim/scenario.h"

namespace sim = navground::sim;

struct MyGroup : public sim::Scenario::Group {
  // add here the logic to populate the world
  void add_to_world(sim::World *world, seed = std::nullopt) override {
    // use the world random generator to sample random variable.
    auto & rng = world->get_random_generator();
    // manipulate the world, in particular create and add agents
    // but you are not restricted to that.
  }
};

Then, you add the group to your scenario

C++Python

MyScenario scenario;
scenario.add_group(std::make_shared<MyGroup>());
// now scenario.init_world(...) will also call this group ``add_to_world``

Note

This is a weaker way to extend a scenario than registering a sub-class as the new groups will not be exposed to YAML.

Initializers

Similar to groups, you can add an initializer (C++, Python) to your scenario, which is a procedure taking a mutable world at argument.

C++Python

MyScenario scenario;
scenario.add_init([](World * world, std::optional<unsigned> seed) {
   ...
});
// now scenario.init_world(...) will also call this function.

Note

Like for groups, initializers are not exposed to YAML and must therefore be added through the API.