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Documentation

This package provides roscpp and rospy bindings for tf2. Here is a list of the common method that should be used when interacting with tf2 function within ROS.

Broadcasting Transforms

$ROS_DISTRO

• tf2_ros::TransformBroadcaster(), constructor

• tf2_ros::TransformBroadcaster::sendTransform to send transforms

Please refer to the C++ API or Python API

Similarly static transforms can be sent by:

• tf2_ros::StaticTransformBroadcaster(), constructor,

• tf2_ros::StaticTransformBroadcaster::sendTransform to send static transforms

Please refer to the C++ API or Python API

Using Published Transforms

For most purposes using tf2_ros will be done using tf2_ros::Buffer. It's main public API is defined by tf2_ros::BufferInterface. Typically it will be populated using a tf2_ros::TransformListener which subscribes to the appropriate topics.

• tf2_ros::Buffer::transform is the main method for applying transforms.

• canTransform allows to know if a transform is available

• lookupTransform is a lower level method which returns the transform between two coordinate frames. This method is the core functionality of the tf2 library.

• getFrames is a service method providing the frames in the graph as a yaml tree

Please refer to the C++ API or Python Api

Filtering Transforms

tf2_ros provides a feature which allows to pass only the messages once there is transform data available. This follows the pattern from the message_filters package. Here is a brief list of functions that the user is most likely to use.

• tf2_ros::MessageFilter(), constructor

• connectInput() allows to connect filters together

• setTargetFrame() set the frame you want to be able to transform to before getting a message callback

• setTargetFrames() set the frames you want to be able to transform to before getting a message callback

• setTolerance() specifies the time tolerance for the transform data

• clear flushes the message queue

• setQueueSize()

Please refer to the C++ API or Python Api

Exceptions

Here is the list of exceptions that can be thrown by tf2_ros and are inherited from tf2.

• tf2::ConnectivityException

• tf2::LookupException

• tf2::ExtrapolationException

• tf2::InvalidArgumentException

• tf2::TimeoutException

• tf2::TransformException

For more information see C++ exceptions or Python Exceptions

Tools

static_transform_publisher

static_transform_publisher x y z yaw pitch roll frame_id child_frame_id

• Publish a static coordinate transform to tf2 using an x/y/z offset in meters and yaw/pitch/roll in radians. (yaw is rotation about Z, pitch is rotation about Y, and roll is rotation about X).

static_transform_publisher x y z qx qy qz qw frame_id child_frame_id

• Publish a static coordinate transform to tf2 using an x/y/z offset in meters and quaternion.

Unlike in tf, there is no period argument, and a latched topic is used.

static_transform_publisher is designed both as a command-line tool for manual use, as well as for use within roslaunch files for setting static transforms. For example:

   1 <launch>
   2 <node pkg="tf2_ros" type="static_transform_publisher" name="link1_broadcaster" args="1 0 0 0 0 0 1 link1_parent link1" />
   3 </launch>