dm_control Unable to load an .xml with bodies which have "user" parameter using "mjcf.from

Hi, I'm a student and I'm trying to use MuJoCo for simulating rigid body dynamics.

I'm looking for some help with setting "user" attribute in "body" elements in .XML files. Reading this section and referring to these lines, I tried to set a user parameter as follows:

<mujoco model="target">
  <size nuser_body="1"/>
  <worldbody>
    <body name="object" user="1.28">
      <geom name="geom" type="box" density="1000" size=".16 .32 .64" rgba="1 0 0 1"/>
    </body>minimal
  </worldbody>
</mujoco>

But I got the following error:

Traceback (most recent call last):
  File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/parser.py", line 210, in _parse_children
    mjcf_child = mjcf_element.add(xml_child.tag, **attributes)
  File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/element.py", line 630, in add
    return self.insert(element_name, position=None, **kwargs)
  File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/element.py", line 655, in insert
    new_element = _make_element(child_spec, self, attributes=kwargs)
  File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/element.py", line 128, in _make_element
    return _ElementImpl(spec, parent, attributes)
  File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/element.py", line 185, in __init__
    self._check_valid_attribute(attribute_name)
  File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/element.py", line 534, in _check_valid_attribute
    raise AttributeError(
AttributeError: 'user' is not a valid attribute for <body>

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/parser.py", line 104, in from_path
    return _parse(xml_root, escape_separators,
  File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/parser.py", line 169, in _parse
    _parse_children(xml_root, mjcf_root, escape_separators)
  File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/parser.py", line 219, in _parse_children
    _parse_children(xml_child, mjcf_child, escape_separators)
  File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/parser.py", line 216, in _parse_children
    raise err_type(
  File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/parser.py", line 210, in _parse_children
    mjcf_child = mjcf_element.add(xml_child.tag, **attributes)
  File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/element.py", line 630, in add
    return self.insert(element_name, position=None, **kwargs)
  File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/element.py", line 655, in insert
    new_element = _make_element(child_spec, self, attributes=kwargs)
  File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/element.py", line 128, in _make_element
    return _ElementImpl(spec, parent, attributes)
  File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/element.py", line 185, in __init__
    self._check_valid_attribute(attribute_name)
  File "/home/atsushi/miniconda3/envs/rigid_body_manip_se3/lib/python3.9/site-packages/dm_control/mjcf/element.py", line 534, in _check_valid_attribute
    raise AttributeError(
AttributeError: Line 4: error while parsing element <body>: 'user' is not a valid attribute for <body>

Does mjcf support .XML files with "body" elements with a "user" parameter in the first place? If it supports, which part should I change in the XML string above?

Thanks in advance,

Apr 06 '24 21:04 barikata1984

Hey, I am a student as well not an expert. I have a similar problem just like you in Issue #457. I have not received any answers yet. But I solved it pretty unprofessionally, it worked tho. Something like this:

xml = env_mjcf.to_xml_string()
xml = xml.replace("<flexcomp ", '<flexcomp dim="3"', 1)
model = mujoco.MjModel.from_xml_string(xml)

You could try the same.

Apr 07 '24 14:04 bakehamster

Hi both.

You probably just need to update mjcf/schema.xml?

Please try and if that solves your problem, send a PR?

Cheers

Apr 07 '24 21:04 yuvaltassa

Hey guys,

On the github version mjcf/schema.xml they are not defined as valid attributes. After manually added the dim attribute to the flexcomp element, it solved my issue.

Thanks for the help.

Regards

Apr 08 '24 17:04 bakehamster

For future visitors looking for a workaround until PR #468 is merged, custom/numeric field can be used without the PR like:

  <custom>
    <numeric name="your_parameter" size="1" data="3.14"/>
  </custom>

May 28 '24 04:05 barikata1984

Unable to load an .xml with bodies which have "user" parameter using "mjcf.from_path()"