Gazebo Gazebo: Using libgazebo

Using libgazebo

Normal users will interact with Gazebo via player and need not be aware of this library. This chapter is included primarily to aid those who either wish to add a new type of interface to the simulator, or who wish to write their own custom control programs (by-passing player entirely).

Python bindings for libgazebo are also available.

Architecture

The details of the underlying IPC are entirely hidden by libgazebo, which should be treated as a black box for passing data back and forth to the server. Currently, the only limitation users need be aware of is that both server and client must reside on the same machine; they cannot be run in separate locations across a network.

Devices and Interfaces

The complete set of interfaces supported by libgazebo is described here. Note that these interfaces should not be confused with the interfaces defined by Player. Currently, these two sets of interfaces are fairly similar, but there is no guarantee that they will remain so in future.

Using libgazebo

// simple.c - works with simple.world
// compile with:
//    gcc -Wall -g3 `pkg-config --cflags gazebo` -c -o simple.o simple.c
//    gcc simple.o -o simple `pkg-config --libs gazebo` 
// Thanks to Kevin Knoedler for various fixes.

#include <stdio.h>
#include <gazebo.h>

int main (int argc, char *argv[])
{
  int i;
  gz_client_t *client;
  gz_position_t *position;
  int server_id;
  int client_id;

  // Assume one server and one client
  server_id = 0;
  client_id = 0;

  // Print all errors
  gz_error_init(1, 9);

  // Create a client object
  client = gz_client_alloc();  

  // Connect to the server
  if (gz_client_connect_wait(client, server_id, client_id) != 0)
    return -1;

  // Create a position interface
  position = gz_position_alloc();

  // Connect to device on server
  if (gz_position_open(position, client, "robot1") != 0)
    return -1;

  // Read some data
  for (i = 0; i < 10; i++)
  {
    // Wait for new data
    gz_client_wait(client);
    
    // Lock it
    gz_position_lock(position, 1);

    // Print the current odometric position
    printf("%0.3f %0.3f\n", 
           position->data->pos[0], position->data->pos[1]); 

    // Unlock it
    gz_position_unlock(position);
  }

  // Close the interface and free object
  gz_position_close(position);
  gz_position_free(position);

  // Close the connection and free the client object
  gz_client_disconnect(client);
  gz_client_free(client);

  return 0;
}

<?xml version="1.0"?>

<gz:world 
  xmlns:gz='http://playerstage.sourceforge.net/gazebo/xmlschema/#gz'
  xmlns:model='http://playerstage.sourceforge.net/gazebo/xmlschema/#model'
  xmlns:sensor='http://playerstage.sourceforge.net/gazebo/xmlschema/#sensor'
  xmlns:window='http://playerstage.sourceforge.net/gazebo/xmlschema/#window'
  xmlns:param='http://playerstage.sourceforge.net/gazebo/xmlschema/#params'
  xmlns:ui='http://playerstage.sourceforge.net/gazebo/xmlschema/#params'>

  <model:ObserverCam>
    <id>userCam0</id>
    <xyz>-0.506 0.894 0.865</xyz>
    <rpy>0 26 -23</rpy>
    <imageSize>640 480</imageSize>
  </model:ObserverCam>

  <model:LightSource>
    <id>light1</id>
    <xyz>0.0 10.0 100.0</xyz>
  </model:LightSource>

  <model:GroundPlane>
    <id>ground1</id>
    <color>0 0.5 0</color>
  </model:GroundPlane>

  <model:Pioneer2AT>
    <id>robot1</id>
    <xyz>0.0 0.0 0</xyz>
  </model:Pioneer2AT>

</gz:world>

Using libgazebo

Architecture

Devices and Interfaces

Using libgazebo

Compiling and Linking Programs With libgazebo