Introduction

Gazebo supports the Razer Hydra controller. You will be able to use this motion and orientation detection controller to interact with your models in Gazebo.

Razer Hydra configuration.

Open a terminal (CTRL-ALT-T), and run the following command:

echo -e "ATTRS{idProduct}==\"0300\",ATTRS{idVendor}==\"1532\",ATTR{bInterfaceNumber}==\"00\",TAG=\"hydra-tracker\"\nSUBSYSTEM==\"hidraw\",TAGS==\"hydra-tracker\", MODE=\"0666\", SYMLINK+=\"hydra\"" > 90-hydra.rules

This will Create a file called 90-hydra.rules.

We need to be able to access to the controller without root access.

sudo cp 90-hydra.rules /etc/udev/rules.d/
sudo udevadm control --reload-rules

Gazebo compilation with Razer Hydra support.

We need to install the optional libusb dependency.

sudo apt-get install libusb-1.0-0-dev

Once Hydra is configured and the extra dependency satisfied, you should be able to compile Gazebo from source with Hydra support.

Follow this instructions to compile Gazebo. During the execution of the cmake command, you should see this message confirming that the SDK is found:

-- Looking for libusb-1.0 - found. Razer Hydra support enabled.

Using Hydra within Gazebo.

Using Hydra in Gazebo requires two steps. The first step is to load the Hydra plugin in your world file.

<!-- Load the plugin for Razer Hydra -->
<plugin name="hydra" filename="libHydraPlugin.so"></plugin>

This plugin will automatically publish messages on the topic ~/hydra.

The second step is to write a plugin that subscribes to the hydra topic and make something interesting. For this tutorial, we are going to move a sphere by using the right joystick of Hydra. A HydraDemoPlugin is available in Gazebo in the plugins/ directory.

Plugin code:

#include <boost/bind.hpp>
#include <gazebo/gazebo.hh>
#include <gazebo/physics/physics.hh>
#include "gazebo/transport/transport.hh"
#include "HydraDemoPlugin.hh"

using namespace gazebo;

GZ_REGISTER_MODEL_PLUGIN(HydraDemoPlugin)

/////////////////////////////////////////////////
HydraDemoPlugin::HydraDemoPlugin()
{
}

/////////////////////////////////////////////////
HydraDemoPlugin::~HydraDemoPlugin()
{
}

/////////////////////////////////////////////////
void HydraDemoPlugin::OnHydra(ConstHydraPtr &_msg)
{
  boost::mutex::scoped_lock lock(this->msgMutex);
  this->hydraMsgPtr = _msg;
}

/////////////////////////////////////////////////
void HydraDemoPlugin::Load(physics::ModelPtr _parent, sdf::ElementPtr /*_sdf*/)
{
  // Get the world name.
  this->model = _parent;
  this->world = this->model->GetWorld();

  // Subscribe to Hydra updates by registering OnHydra() callback.
  this->node = transport::NodePtr(new transport::Node());
  this->node->Init(this->world->GetName());
  this->hydraSub = this->node->Subscribe("~/hydra",
      &HydraDemoPlugin::OnHydra, this);

  // Listen to the update event. This event is broadcast every
  // simulation iteration.
  this->updateConnection = event::Events::ConnectWorldUpdateBegin(
      boost::bind(&HydraDemoPlugin::Update, this, _1));
}

/////////////////////////////////////////////////
void HydraDemoPlugin::Update(const common::UpdateInfo & /*_info*/)
{
  boost::mutex::scoped_lock lock(this->msgMutex);

  // Return if we don't have messages yet
  if (!this->hydraMsgPtr)
    return;

  // Read the value of the right joystick.
  double joyX = this->hydraMsgPtr->right().joy_x();
  double joyY = this->hydraMsgPtr->right().joy_y();

  // Move the sphere.
  this->model->SetLinearVel(math::Vector3(-joyX * 0.2, joyY * 0.2, 0));

  // Remove the message that has been processed.
  this->hydraMsgPtr.reset();
}

Before launching Gazebo, we need to include our model plugin in a world file. Here is the complete world file of the tutorial (also available under worlds/hydra_demo.world).

<?xml version="1.0" ?>
<sdf version="1.4">
  <world name="default">

    <!-- A ground plane -->
    <include>
      <uri>model://ground_plane</uri>
    </include>

    <!-- A global light source -->
    <include>
      <uri>model://sun</uri>
    </include>

    <!-- Load the plugin for Razer Hydra -->
    <plugin name="hydra" filename="libHydraPlugin.so">
      <pivot>0.04 0 0</pivot>
      <grab>0.12 0 0</grab>
    </plugin>

    <!-- A sphere controlled by Hydra-->
    <model name="sphere">
      <pose>0 0 0 0 0 0</pose>
      <link name="link">
        <collision name="collision">
          <geometry>
            <sphere>
              <radius>0.5</radius>
            </sphere>
          </geometry>
        </collision>
        <visual name="visual">
          <geometry>
            <sphere>
              <radius>0.5</radius>
            </sphere>
          </geometry>
        </visual>
      </link>

      <plugin name='sphere_ctroller' filename='libHydraDemoPlugin.so'></plugin>

    </model>

</world>
</sdf>

It is time to run Gazebo and use the Hydra's right joystick to move the sphere. Do not forget to plug your Hydra, and then:

gazebo worlds/hydra_demo.world