Hi,
Hi,

I'm trying to assemble some laser scans into a point cloud using
laser_assembler tutorial [1] but the periodic_snapshotter keeps
reporting that it is only publishing empty messages with zero points:
    [ INFO] [1280258736.674914761, 1275001489.217034967]: Published
Cloud with 0 points

On closer investigation this seems to be caused by a TF_OLD_DATA error
generated by scan_assembler.  Is there a recent change to how the time
mechanism works in ROS?  I'm running all these nodes on the same
computer, using --clock with "rosbag play" (on the provided bag file
laser.bag), and tried to run with /use_sim_time=True but the error
still persist.

TF error:
Node: /scan_assembler
Time: 1275001492.698066055
Severity: Warn
Location: /opt/ros/cturtle/stacks/geometry/tf/src/tf.cpp:Transformer::setTransform:179
Published Topics: /rosout

TF_OLD_DATA ignoring data from the past for frame /sensor_mount_link
at time 1.275e+09 according to authority /play_1280258731455287347
Possible reasons are listed at

My launch file for laser_assembler:
<launch>
<node pkg="laser_assembler" type="point_cloud_assembler" name="scan_assembler">
    <remap from="scan" to="tilt_scan"/>
    <param name="fixed_frame" value="base_footprint"/>
</node>
</launch>



[1] http://www.ros.org/wiki/laser_assembler/Tutorials/HowToAssembleLaserScans
-- 
Hai Nguyen
CS, Robotics