I've been stepping through the first PR2 arm motion planning tutorial
(http://www.ros.org/wiki/motion_planning_environment/Tutorials/Making%20collision%20maps%20from%20self-filtered%20tilting%20laser%20data)
and I have a couple of questions...

When I first launch rviz_collision_tutorial_1.launch, I see a cluster
of points lit up roughly where I think it's reasonable that the laser
scanner should be getting returns from the pole.  When I launch
laser-perception.launch, I see that series of points traverse down the
pole, lighting up the tips of the grippers along the way.  The cluster
of points on the grippers turn black about 1/2 way down the gripper
and stay black as they traverse down the arm and back up again, where
they turn white once again.  Similarly, the clusfer of points on the
pole dim about 1/2 way down and, as best as I can tell, at exactly the
same time that the cluster of points on the grippers turn dark.  They
turn bright again when the scan goes back up the pole.

After the scan has traced all (or most?) of the way down the pole, I
see a very straight white line trace diagonally down across the rviz
scene, change direction, and go back up again, followed shortly after
by the cluster of points traversing the pole and the arms.

Do other folks see similar behavior?  If so, what causes the laser
scan display to turn dark (or dim) and what causes the straight white
line?

When I first saw the straight white line, I thought it was the laser
scan itself, but now that I've run it a few times and understand (most
of the rest of what) I'm seeing, I'm not sure what the source of it is
(except that it is related to the laser scan itself).  I see the
behavior of the white points turning dark/dim for both the laser scan
topic and the point cloud topic.

--wpd