Class BufferCore

Nested Relationships

Nested Types

Inheritance Relationships

Base Type

Class Documentation

class BufferCore : public tf2::BufferCoreInterface

A Class which provides coordinate transforms between any two frames in a system.

This class provides a simple interface to allow recording and lookup of relationships between arbitrary frames of the system.

libTF assumes that there is a tree of coordinate frame transforms which define the relationship between all coordinate frames. For example your typical robot would have a transform from global to real world. And then from base to hand, and from base to head. But Base to Hand really is composed of base to shoulder to elbow to wrist to hand. libTF is designed to take care of all the intermediate steps for you.

Internal Representation libTF will store frames with the parameters necessary for generating the transform into that frame from it’s parent and a reference to the parent frame. Frames are designated using an std::string 0 is a frame without a parent (the top of a tree) The positions of frames over time must be pushed in.

All function calls which pass frame ids can potentially throw the exception tf::LookupException

Public Types

using TransformableCallback = std::function<void(TransformableRequestHandle request_handle, const std::string &target_frame, const std::string &source_frame, TimePoint time, TransformableResult result)>

Public Functions

explicit BufferCore(tf2::Duration cache_time = BUFFER_CORE_DEFAULT_CACHE_TIME)

Constructor

Parameters:

cache_time – How long to keep a history of transforms in nanoseconds

virtual ~BufferCore(void)
virtual void clear() override

Clear all data.

bool setTransform(const geometry_msgs::msg::TransformStamped &transform, const std::string &authority, bool is_static = false)

Add transform information to the tf data structure.

Parameters:

  • transform – The transform to store

  • authority – The source of the information for this transform

  • is_static – Record this transform as a static transform. It will be good across all time. (This cannot be changed after the first call.)

Returns:

True unless an error occured

virtual geometry_msgs::msg::TransformStamped lookupTransform(const std::string &target_frame, const std::string &source_frame, const TimePoint &time) const override

Get the transform between two frames by frame ID.

Possible exceptions tf2::LookupException, tf2::ConnectivityException, tf2::ExtrapolationException, tf2::InvalidArgumentException

Parameters:

  • target_frame – The frame to which data should be transformed

  • source_frame – The frame where the data originated

  • time – The time at which the value of the transform is desired. (0 will get the latest)

Returns:

The transform between the frames

virtual geometry_msgs::msg::TransformStamped lookupTransform(const std::string &target_frame, const TimePoint &target_time, const std::string &source_frame, const TimePoint &source_time, const std::string &fixed_frame) const override

Get the transform between two frames by frame ID assuming fixed frame.

Possible exceptions tf2::LookupException, tf2::ConnectivityException, tf2::ExtrapolationException, tf2::InvalidArgumentException

Parameters:

  • target_frame – The frame to which data should be transformed

  • target_time – The time to which the data should be transformed. (0 will get the latest)

  • source_frame – The frame where the data originated

  • source_time – The time at which the source_frame should be evaluated. (0 will get the latest)

  • fixed_frame – The frame in which to assume the transform is constant in time.

Returns:

The transform between the frames

geometry_msgs::msg::VelocityStamped lookupVelocity(const std::string &tracking_frame, const std::string &observation_frame, const TimePoint &time, const tf2::Duration &averaging_interval) const
geometry_msgs::msg::VelocityStamped lookupVelocity(const std::string &tracking_frame, const std::string &observation_frame, const std::string &reference_frame, const tf2::Vector3 &reference_point, const std::string &reference_point_frame, const TimePoint &time, const tf2::Duration &duration) const

Lookup the velocity of the moving_frame in the reference_frame.

Possible exceptions TransformReference::LookupException, TransformReference::ConnectivityException, TransformReference::MaxDepthException

Parameters:

  • reference_frame – The frame in which to track

  • moving_frame – The frame to track

  • time – The time at which to get the velocity

  • duration – The period over which to average

  • velocity – The velocity output

virtual bool canTransform(const std::string &target_frame, const std::string &source_frame, const TimePoint &time, std::string *error_msg = nullptr) const override

Test if a transform is possible.

Parameters:

  • target_frame – The frame into which to transform

  • source_frame – The frame from which to transform

  • time – The time at which to transform

  • error_msg – A pointer to a string which will be filled with why the transform failed, if not nullptr

Returns:

True if the transform is possible, false otherwise

virtual bool canTransform(const std::string &target_frame, const TimePoint &target_time, const std::string &source_frame, const TimePoint &source_time, const std::string &fixed_frame, std::string *error_msg = nullptr) const override

Test if a transform is possible.

Parameters:

  • target_frame – The frame into which to transform

  • target_time – The time into which to transform

  • source_frame – The frame from which to transform

  • source_time – The time from which to transform

  • fixed_frame – The frame in which to treat the transform as constant in time

  • error_msg – A pointer to a string which will be filled with why the transform failed, if not nullptr

Returns:

True if the transform is possible, false otherwise

virtual std::vector<std::string> getAllFrameNames() const override

Get all frames that exist in the system.

std::string allFramesAsYAML(TimePoint current_time) const

A way to see what frames have been cached in yaml format Useful for debugging tools.

std::string allFramesAsYAML() const

Backwards compatibility for #84

std::string allFramesAsString() const

A way to see what frames have been cached Useful for debugging.

TransformableRequestHandle addTransformableRequest(const TransformableCallback &cb, const std::string &target_frame, const std::string &source_frame, TimePoint time)

Internal use only.

void cancelTransformableRequest(TransformableRequestHandle handle)

Internal use only.

inline void setUsingDedicatedThread(bool value)
inline bool isUsingDedicatedThread() const
bool _frameExists(const std::string &frame_id_str) const

Check if a frame exists in the tree.

Parameters:

frame_id_str – The frame id in question

bool _getParent(const std::string &frame_id, TimePoint time, std::string &parent) const

Fill the parent of a frame.

Parameters:

  • frame_id – The frame id of the frame in question

  • time – The timepoint of the frame in question

  • parent – The reference to the string to fill the parent Returns true unless “NO_PARENT”

void _getFrameStrings(std::vector<std::string> &ids) const

A way to get a std::vector of available frame ids.

inline CompactFrameID _lookupFrameNumber(const std::string &frameid_str) const
inline CompactFrameID _lookupOrInsertFrameNumber(const std::string &frameid_str)
inline tf2::TF2Error _getLatestCommonTime(CompactFrameID target_frame, CompactFrameID source_frame, TimePoint &time, std::string *error_string) const
inline CompactFrameID _validateFrameId(const char *function_name_arg, const std::string &frame_id) const
inline tf2::Duration getCacheLength()

Get the duration over which this transformer will cache.

std::string _allFramesAsDot(TimePoint current_time) const

Backwards compatabilityA way to see what frames have been cached Useful for debugging.

std::string _allFramesAsDot() const
void _chainAsVector(const std::string &target_frame, TimePoint target_time, const std::string &source_frame, TimePoint source_time, const std::string &fixed_frame, std::vector<std::string> &output) const

Backwards compatabilityA way to see what frames are in a chain Useful for debugging.

Public Static Attributes

static const uint32_t MAX_GRAPH_DEPTH = 1000UL

< Maximum graph search depth (deeper graphs will be assumed to have loops)