#View MuJoCo (MJCF) models

URDF Studio opens MuJoCo models (MJCF, the <mujoco> XML format) read-only. Joints, the Inspector, Checks, collision view, measuring and exports all work the same way as for URDF.

The Unitree Go2 from MuJoCo Menagerie

#Open a model

Open the folder that contains the model, as you would a ROS package — for example one robot from MuJoCo Menagerie. URDF Studio finds every .xml file whose root element is <mujoco> and lists it with the other robot files. Menagerie's scene.xml (robot plus floor and lights) is listed first.

In VS Code, .mjcf files open in the preview directly. For .xml files, use the Open Preview button in the editor title bar or the URDF Studio: Open Preview command; the file must be a MuJoCo model.

Include the whole model folder: meshes and <include> files are found relative to the main model file and its meshdir.

#How MJCF is shown

URDF Studio converts the model to URDF for display. The Source tab shows that URDF, marked converted from MJCF. Your MJCF file is never changed; Ctrl+S in the Source tab saves the converted URDF as a separate .urdf file, which is a handy way to get a URDF from an MJCF model.

MJCF	Shown as
`<body>`	A link
`hinge` joint	Revolute joint, or continuous when it has no limits
`slide` joint	Prismatic joint
Several joints in one body	A chain of joints, in the same order
`ball`, `free` joint	Fixed — URDF has no equivalent
Geoms in groups 0–2	Visual geometry
Geoms that collide (`contype` / `conaffinity` not both 0)	Collision geometry
`capsule`	A cylinder with a sphere at each end
`ellipsoid`	A sphere of the largest radius
Infinite `plane` (the floor)	Not drawn — the 3D view has its own grid

Default classes, childclass, <frame>, <include>, fromto, every orientation form (quat, euler with eulerseq, axisangle, xyaxes, zaxis) and angle="degree" are supported. Joint positions match MuJoCo's own kinematics.

When something can't be shown exactly — a ball or free joint, an ellipsoid, a height field — a note appears under Loading problems in the Checks tab, naming what was approximated.

#Differences from URDF to keep in mind

No "missing inertia" warnings. MuJoCo computes mass and inertia from the geoms when a body has no <inertial>, so check P-001 is skipped.
Floating bases stay put. A body with a free joint, such as a legged robot's base, is drawn at its starting position. Its leg joints move normally.
Not shown: actuators, tendons, equality constraints, sensors, sites, textures, height fields and meshes defined by inline vertices.