Questions to SDF, urdf, xacro, material, textures using Gazebo

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Hi Guys,

Currently I am a little stuck with my xacro model.

I have a texture file which should be attached to a surface in the xacro. How to add materials to your package, what do I need to export (what could I export) in the package.xml

Where do I really find the stuff documenting this features.

Examples:

            <material>
                <script>
                    <name>a/mat</name>
                    <uri>model://some_model/materials/scripts/mat.material</uri>
                </script>
            </material>

I have seen that for url there can be file and model. Does package also work here? What are those replaced with in the end and which of these exist?

Next: in the material file:

 material a/mat
{
  technique
  {
    pass
    {
      ambient 0.5 0.5 0.5 1.0
      diffuse 1.0 1.0 1.0 1.0
      specular 0.0 0.0 0.0 1.0 0.5

      texture_unit
      {
        texture file.png
        filtering trilinear
      }
    }
  }
}

From where and how does it know where file.png is?

Does it just go standard for "../textures" ?

Folder structure is mostly like

• package
  • models
    • myModel
      • textures
      • scripts

It works for me in a sdf file, but it seems to work never in my xacro.

Somehow this is related to the package.xml as well where you export model or media path I found as well:

<export>    
  <gazebo_ros gazebo_media_path="${prefix}"/> 
</export>

or:

<export>    
  <gazebo_ros gazebo_model_path="${prefix}/models"/> 
</export>

Are there any others and what exactly do they do?

Which variable does that set? Can I see them in my environment?

How are they supposed to be set up correctly - any standard way?

What if for example I want to do a package with materials for gazebo, which should can be used for any package, how do I set that up?

So that I can use them, as you normally can do with "Gazebo/Grey ", "Gazebo/White"

Example*1 (xacro):

  <gazebo reference="link">
    <material>Gazebo/Grey</material>
  </gazebo>

Can somebody just enlighten me how to do it or where I find the documentation for all these things to make it "just right"?

UPDATE ---

I have now checked out multiple locations and found different places to get information about this thing, also found how to debug it.

http://gazebosim.org/tutorials?tut=ros_roslaunch

there it says:

rospack plugins --attrib="gazebo_media_path" gazebo_ros

And I saw that I actually had a problem. It only takes these if you have a <run _depend> on gazebo_ros.

  <run_depend>gazebo_ros</run_depend>


    <export>    
      <gazebo_ros gazebo_media_path="${prefix}/media"/> 
    </export>

But I still do not get my material like that*1.

Update 2:

Just when looking at my own old xacros I found out, you can instead of *1 also do:

  <gazebo reference="link">
        <material value="Gazebo/Grey" />
  </gazebo>

So another Question raised up: Which is now the "prefered" way of doing that?

Which one is deprecated?

Thanks a lot,

Regards,

Christian