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

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: 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: or: 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/Grey 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](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 `` on **gazebo_ros**. gazebo_ros --- 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: So another Question raised up: **Which is now the "prefered" way of doing that?** **Which one is deprecated?** ______________________ Thanks a lot, Regards, Christian