Getting the gazebo plugin p3d working (hydro)

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Ros Hydro; Gazebo 1.9.2;

Hello guys,

The last 2 days I am trying to figure out how to get this little plugin to work:

<gazebo>
<plugin name="my_box_controller" plugin="libros_p3d.so">
  <alwaysOn>true</alwaysOn>
  <updateRate>100.0</updateRate>
  <bodyName>base_link</bodyName>
  <topicName>mObstacle_GT</topicName>
  <gaussianNoise>0.0</gaussianNoise>
  <frameName>base_link</frameName>
  <!--interface:position name="my_box_p3d_position_iface" /-->
</plugin>

</gazebo>

and this is the error that I get

Error [parser.cc:492] Required attribute[filename] in element[plugin] is not specified in SDF.

I bet I got confused with the whole URDF, XACRO, SDF stuff. I could post the rest of my code, even though it is just a box. Also, it might be worth mentioning that everything works fin when I remove the plugin.

Of course I looked at the tutorial but it was not very helpful (or did I miss something?): http://gazebosim.org/wiki/Tutorials/1.9/ROSMotorandSensorPlugins#P3D.283DPositionInterfaceforGroundTruth.29

Thanks in advance guys, Marcus