How to resize meshes in URDF?

Question

I am currently drawing out my robot using URDF. I am at the end of the first URDF tutorial (see http://wiki.ros.org/urdf/Tutorials/Building%20a%20Visual%20Robot%20Model%20with%20URDF%20from%20Scratch#Finishing_the_Model). My problem: once I added my mesh, it is very disproportionate to the rest of the drawing, and I have no idea how to resize the mesh. The tutorial states that: "Meshes can also be sized using relative scaling parameters or a bounding box size"

where do I find an example? Where is the documentation? and if no documentation or examples exist, could you please provide an example of code for a "bounding box" or "relative scaling"?

More detail:

image before meshes are added in urdf file:

image after meshes are added in urdf file:

the code importing the meshes:

   <!-- *********************(21) LMS LINK - MESHES****************************-->
  <!-- a "link" is the part that we are creating. All the internal tags describe
       this part. This is the body of Jimmy (both square levels) -->
  <link name="LMS_link">
    <visual>
      <geometry>
        <!--box dimensions is Meters. L X W X H where the L X H is a rectangle, 
            and the H extrudes it upwards -->
        <mesh filename="package://urdf_tutorial/meshes/LMS-200-30106.dae"/>
      </geometry>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <material name="white"/>
    </visual>
  </link>
    
    <!-- *********************(22) LMS to LMS PLATE JOINT **********************-->
    <!-- a joint allows us to create a relationship between two links (parts)-->
      <joint name="LMS_to_LMS_plate_joint" type="fixed">
        <parent link="LMS_plate_link"/>
        <child link="LMS_link"/>
        <!-- this is the point at which the two parts attach to one another-->
        <origin xyz="0 0 0"/>
      </joint>

I am building a URDF because it was suggested here: https://answers.ros.org/question/271819/please-suggest-all-packages-to-achieve-slam-for-robot/

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Originally posted by BuilderMike on ROS Answers with karma: 247 on 2017-10-18

Post score: 5

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Original comments

Comment by gvdhoorn on 2017-10-19:
@BuilderMike: please attach your images to your question directly. I've given you enough karma to do that.

Comment by gvdhoorn on 2017-10-19:
Also: I would advise you follow regular ROS Naming conventions when naming links and joints as well. In summary: no capitals, anywhere, no whitespace, no special chars.

Comment by BuilderMike on 2017-10-19:
@gvdhoorn Thanks for the karma, I updated all my questions to include images instead of links. Also, thank you for the link to the URDF XML wiki.... I missed it when reading the tutorial. As for the naming convention, thanks for pointing out my error. Is there a document outlining these conventions?

Comment by gvdhoorn on 2017-10-20:
re: conventions: I think I linked you to those ("ROS Naming conventions").

If you're looking for joint/link/frame naming conventions, there is geometry/CoordinateFrameConventions, but it's not too explicit.

No capitals or special chars ..

Comment by gvdhoorn on 2017-10-20:
.. and no whitespace just makes sense: no guessing as to how someone CaPiTaLiseD their frames, no weird international char / localisation issues, etc.

I always follow wiki/Names with everything (files, directories, xacros, etc).

Answer 1

This should do it:

<mesh filename="package://pkg_name/filepath/your_stl.stl" scale="0.001 0.001 0.001"/>

Alternatively, you could install Blender. It lets you scale stl's and also change the coordinate frame. See http://gazebosim.org/tutorials?tut=guided_i2

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Originally posted by AndyZe with karma: 2331 on 2017-10-18

This answer was ACCEPTED on the original site

Post score: 11

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Original comments

Comment by BuilderMike on 2017-10-18:
Hi AndyZe, Thanks for your answer and suggestion, At this point, I have so many packages to learn that it's overwhelming. Could you expand your answer on what the scale values mean? is it % or actual distance units, and if so which ones? Is there any documentation for this xml tag in a URDF context?

Comment by AndyZe on 2017-10-18:
It's just multiplied by that factor. So in my example, the STL would be 1/1000th of the original size.

Comment by BuilderMike on 2017-10-18:
How did you know this... is there documentation on this xml tag somewhere? Thank you very much for your answer it did work for me.

Comment by AndyZe on 2017-10-18:
Tribal knowledge. But seriously, I learned it from another person firsthand.

Comment by gvdhoorn on 2017-10-19:\

Tribal knowledge

This is all documented on the wiki, see wiki/urdf/XML.

Comment by lucasw on 2021-09-21:
Negative scale values do a flip/mirror image on that axis, a left wheel can become a right wheel and so on, which is less trouble than having to maintain separate otherwise identical mesh files.