How to import stl files into urdf files

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I am trying to use stl files with the tag mesh with this code:

  <geometry>
    <mesh filename="package://auriga_model/auriga_base.stl"/>
  </geometry>

The package existes and the file is located there but I get this message when I try to launch it:

[ERROR] [1301591093.704357996]: Malformed geometry for Visual element
[ERROR] [1301591093.704545807]: Could not parse visual element for Link '/base_laser'
[ERROR] [1301591093.704624976]: link xml is not initialized correctly

I have been doing some test with PR2 stl model and I had no success. Here are some of my tries:

  <!-- description of the robot -->
  <link name="/base_link">
    <visual>
      <origin rpy="0 0 0" xyz="0.15 0 0.35"/>
      <geometry>
        <!-- mesh filename="package://auriga_model/meshes/auriga_base.stl" /-->
        <!-- mesh filename="package://auriga_model/meshes/head_pan.stl" /-->
        <mesh filename="package://pr2_description/meshes/head_v0/head_pan.stl"/>
      </geometry>
    </visual>
  </link>

  <link name="/base_laser">
    <visual>
      <origin rpy="0 0 0" xyz="0 0 0"/>
    </visual>
  </link>

For me, it looks like it can't resolve properly "filename="package://". Is it possible? I tested and "rospack find" command works fine with me.

Any clue?

Now I am able to load PR2 models but not the one of my robot. The original model was build in solidworks and maybe this is the problem. I will try to port it from Catia and I will say if it works.