apply

Transform message entities into target frame

Syntax

tfentity = apply(tfmsg,entity)

Description

tfentity = apply(tfmsg,entity) applies the transformation represented by the 'TransformStamped' ROS message to the input message object entity.

This function determines the message type of entity and apples the appropriate transformation method to it. If the object cannot handle a particular message type, then MATLAB^® displays an error message.

If you want to use only the most current transformation, call transform instead. If you want to store a transformation message for later use, call getTransform, and then call apply.

Note

apply will be removed. Use rosApplyTransform instead. For more information, see ROS Message Structure Functions

Examples

Apply A Transformation To A Point

Connect to a ROS network to get a TransformStamped ROS message. Specify the IP address to connect. Create a transformation tree and get the transformation between desired frames.

rosinit('192.168.17.129')

Initializing global node /matlab_global_node_73610 with NodeURI http://192.168.17.1:55060/

tftree = rostf;
pause(1);
tform = getTransform(tftree,'base_link','camera_link',...
                     rostime('now'),'Timeout',5);

Create a ROS Point message and apply the transformation. You could also get point messages off the ROS network.

pt = rosmessage('geometry_msgs/PointStamped');
pt.Header.FrameId = 'camera_link';
pt.Point.X = 3;
pt.Point.Y = 1.5;
pt.Point.Z = 0.2;

tfpt = apply(tform,pt);

Shut down ROS network.

rosshutdown

Shutting down global node /matlab_global_node_73610 with NodeURI http://192.168.17.1:55060/

Input Arguments

tfmsg — Transformation message

TransformStamped ROS message handle

Transformation message, specified as a TransformStamped ROS message handle. The tfmsg is a ROS message of type: geometry_msgs/TransformStamped.

entity — ROS message

Message object handle

ROS message, specified as a Message object handle.

Supported messages are:

• geometry_msgs/PointStamped

• geometry_msgs/PoseStamped

• geometry_msgs/PointCloud2

• geometry_msgs/QuaternionStamped

• geometry_msgs/Vector3Stamped

Output Arguments

tfentity — Transformed ROS message

Message object handle

Transformed ROS message, returned as a Message object handle.

Version History

Introduced in R2019b

R2021a: ROS Message Structure Functions

You can now create messages as structures with fields matching the message object properties. Using structures typically improves performance of creating, updating, and using ROS messages, but message fields are no longer validated when set. Message types and corresponding field values from the structures are validated when sent across the network.

To support message structures as inputs, new functions that operate on specialized ROS messages have been provided. These new functions are based on the existing object functions of message objects, but support ROS and ROS 2 message structures as inputs instead of message objects.

The object functions will be removed in a future release.

Message Types	Object Function Name	New Function Name
Image CompressedImage	readImage writeImage	rosReadImage rosWriteImage
LaserScan	readCartesian readScanAngles lidarScan plot	rosReadCartesian rosReadScanAngles rosReadLidarScan rosPlot
PointCloud2	apply readXYZ readRGB readAllFieldNames readField scatter3	rosApplyTransform rosReadXYZ rosReadRGB rosReadAllFieldNames rosReadField rosPlot
Quaternion	readQuaternion	rosReadQuaternion
OccupancyGrid	readBinaryOccupanyGrid readOccupancyGrid writeBinaryOccupanyGrid writeOccupanyGrid	rosReadOccupancyGrid rosReadBinaryOccupancyGrid rosReadOccupancyGrid rosWriteBinaryOccupancyGrid rosWriteOccupancyGrid
Octomap	readOccupancyMap3D	rosReadOccupancyMap3D
PointStamped PoseStamped QuaternionStamped Vector3Stamped TransformStamped	apply	rosApplyTransform
All messages	showdetails	rosShowDetails