Hi Grace,

I came across something similar last week. In my case, adding a third
link "fixed it," (i.e, 2 joints, 3 links), since an error check inside
the state publisher was failing if there were only two resulting
transforms.

-Morgan



On Tue, Jun 22, 2010 at 9:54 AM,  <yeongrace.lee@gmail.com> wrote:
> Hi everyone,
>
> My name is Grace Lee and I am an undergraduate research assistant at USC's
> Interaction Lab. I am currently writing a urdf for a human model that will
> be interacting with PR2 in the gazebo. When I run the command "roslaunch" on
> my launch file, I get this error: [ERROR] 1277225053.038870000: Could not
> compute link poses. The tree or the state is invalid.
>
> I have parsed the urdf and the tree structure seems correct - i.e. $ rosrun
> urdf check_urdf [my_urdf_name].xml shows that there is one child (which is
> correct btw). The urdf and the state_publisher.cpp seems to be correct as
> well. Any insights into the source of this problem would be greatly
> appreciated.
>
> Sincerely,
>
> Grace Lee
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