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2014-01-28 17:26:49 -0500 marked best answer tf extrapolation exception using ros::Time(0)

I'm trying to get the latest transform between two frames. What's wrong with this code?

listener.waitForTransform(target_frame, source_frame,      ros::Time(0),ros::Duration(.1));
tf::StampedTransform st;
listener.lookupTransform(target_frame, source_frame, ros::Time(0), st);


terminate called after throwing an instance of 'tf::ExtrapolationException'
  what():  Lookup would require extrapolation into the future.  Requested time 1341794988.800442521 but the latest data is at time 1341794988.782343800, when looking up transform from frame [/openni_rgb_optical_frame] to frame [/base_footprint]

EDIT: I got this error while playing back a bag file. When I set the parameter use_sim_time true, the error disappeared. I'm still mystified, though.

2014-01-28 17:24:55 -0500 marked best answer kinect: nonsense point clouds for 30 seconds after subscribing

I launch the kinect driver and processing nodes with openni_launch/launch/openni.launch. I have the latest versions of the ROS-openni packages in Electric. I get xyzrgb point clouds, but the depth data is nonsense for 30 seconds after subscribing. Here's a video, where I'm viewing the point cloud in rviz on a remote computer: http://surgical1.cs.berkeley.edu/troubleshooting/rviz_kinect.ogv. This isn't a network issue--I have the exact same problem when I record data on the local computer that the kinect is connected to--c1 on the pr2.

2014-01-28 17:22:56 -0500 marked best answer 3d mesh model of robot based on joint states

I want to determine the projection of the robot arms (PR2) onto its cameras so that I can mask these regions out of the images. Has anyone done this before? I see some relevant code in the robot_self_filter package but it's not obvious how to proceed.

2014-01-28 17:22:37 -0500 marked best answer storing 3d range data for localization

As I understand it, the typical way to use the navigation stack with a laser range finder is this: drive around and collect range data, filling up the voxel grid, then save the 2D occupancy grid. Then the next day, you load this map, and amcl localizes the robot by comparing the new range data to the saved map.

It seems like localization would work better if you saved the 3D data and used that. Why doesn't the navigation stack use a 3d map?

2014-01-28 17:22:30 -0500 marked best answer Hang on wait_for_server() on import, but not direct use

I have a function called gripper.py with the lines

grip_r_client = actionlib.SimpleActionClient('r_gripper_controller/gripper_action', Pr2GripperCommandAction)
print "waiting for right gripper server"
grip_r_client.wait_for_server()

Then I have a script, test_gripper.py. If I try to import gripper.py, the program gets stuck at wait_for_server(). On the other hand, if I just copy those lines into test_gripper.py, or if I do execfile('gripper.py'), it works.

What's going on?

Edit: here's the full code. I would upload the package, but I don't have enough karma.

gripper.py:

import roslib
roslib.load_manifest('test')
import rospy, actionlib
from pr2_controllers_msgs.msg import Pr2GripperCommandAction
grip_r_client = actionlib.SimpleActionClient('r_gripper_controller/gripper_action',Pr2GripperCommandAction)
print "waiting for right gripper server"
grip_r_client.wait_for_server()

test_gripper.py:

import roslib
roslib.load_manifest('test')
import rospy,actionlib
rospy.init_node('test_gripper') 
import gripper
# OR ...
#execfile("gripper.py")

I realize this is non-idiomatic code, and it's really easy to fix the problem (I create a Gripper class, and wait_for_server in its __init__ method), but it's a strange phenomenon.

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2013-06-13 10:59:49 -0500 commented answer CMake search path

What variable or file does ROS modify when it gets installed, which adds it to the front of the search path? CMAKE_PREFIX_PATH is unset on my machine.

2013-06-06 08:35:14 -0500 asked a question CMake search path

ROS installation somehow sets CMake the search path to point to favor ROS packages in /opt/ros. I want find_package(PCL) to choose the version in /usr/lib rather than /opt/ros/groovy (The ROS version is missing all of the Grabber stuff) How can I prevent this behavior? Is there some environment variable I need to set?

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