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The SMURF format uses URDF at its heart for defining the kinematic model of a robot. URDF was created in the ROS world and contains only sparse information beyond the "mechanical skeleton" of a robot. Thus, the SMURF format encompasses additional files adding all information that is needed by MARS and in fact any custom-defined data one wants to assign to arbitrary parts of the robot. Thus, Phobos is designed to assist the user in building a viable URDF robot model in Blender and annotate all additional information in SMURF which allows the simulation of the robot in MARS or any custom-tailored tools.

Phobos exports some more formats like SRDF, YAML, submechanisms etc. However, as these are not widely known or used, these are not listed here.

Since release 1.0 Phobos is able to import, edit and export SDF models. SDF is developed as part of the simulation suite Gazebo, which is widely used for robotic applications in the ROS world. It is an advanced format, that contains many additional features and custom scripts, that have reached a complexity, Phobos can not (yet) deal with. For the moment, basic models and most of the common functionality (links, visuals, collisions, sensors, inertias etc.) is implemented. More can be included if there is sufficient interest from the community to support further development.

URDF (the Unified Robot Description Format) enjoys some wide acceptance in the robotics community. It is a rather basic format, that has its own flaws, but is supported my most frameworks for robotic applications. As such, it is deeply connected to Phobos, which acts as an editor for URDF models. Phobos fulfills this job to a high level, allowing the user to import, edit and export models, that are Git compatible and intuitive. However, there are more useful features, which will be available only when using other formats (such as SMURF and SDF).

Note, that you can basically import any mesh file, that Blender can import. There are add-ons out there, which might help you with your specific format. The mesh formats above are listed mainly for their export functionality in the model export of Phobos.

Meshes can be exported in different orientations in Blender. It is possible to define which axis points up and which forward when forming a right-handed frame. Simulators may use different conventions when importing meshes. Therefore we had a look on several simulators in the Phobos' Habitat to ensure compatibility.

The details:

facet normal -1.000000 0.000000 0.000000
outer loop
vertex 0.000000 0.000000 3.000000
vertex 0.000000 2.000000 0.000000
vertex 1.000000 0.000000 0.000000
endloop

o zupyforward
v 0.000000 2.000000 0.000000
v 1.000000 0.000000 0.000000
v 0.000000 0.000000 3.000000
...

...
    <library_geometries>
        <geometry id="zupyforward-mesh" name="zupyforward">
          <mesh>
            <source id="zupyforward-mesh-positions">
              <float_array id="zupyforward-mesh-positions-array" count="255">0.000000 2.000000 0.000000 1.000000 0.000000 0.000000 0.000000 0.000000 3.000000 ...</float_array>
              <technique_common>
                <accessor source="#zupyforward-mesh-positions-array" count="85" stride="3">
                  <param name="X" type="float"/>
                  <param name="Y" type="float"/>
                  <param name="Z" type="float"/>
                </accessor>
              </technique_common>
            </source>
        ...
    ...
...

<robot name="mesh_orientation_tester" version="1.0">
  <link name="root">
    <visual name="zupyforward">
      <origin rpy="0.0 0.0 0.0" xyz="0.0 0.0 0.0"/>
      <geometry>
        <mesh filename="zupyforward.dae" scale="1.0 1.0 1.0"/>
      </geometry>
    </visual>
    <collision name="zupyforward_collision">
      <origin rpy="0.0 0.0 0.0" xyz="0.0 0.0 0.0"/>
      <geometry>
        <mesh filename="zupyforward.dae" scale="1.0 1.0 1.0"/>
      </geometry>
    </collision>
  </link>
</robot>

As URDF/SDF give transformations from root->link->mesh the orientation of the mesh is clearly defined. One could expect that the mesh will be placed accordingly. As the test URDF, presented above, has only zero transformations and the mesh is oriented in all tested mesh formats without any orientation, I'd expect that in all simulators the X-arm of the mesh will point in X-direction, Y-arm in Y-direction and Z-arm in Z-direction.

Note: OSG Based software may have a flaw on importing meshes and there rotations. This is an issue already known for quite a while: https://osg-users.openscenegraph.narkive.com/nhqajNbb/coordinate-system-in-all-readerwriters

import pybullet as pb
pb.connect(pb.GUI)
pb.loadURDF("mesh_orientation_tester.urdf")