URDF VS MJCF
MuJoCo supports URDF because many robots already use it, but its documentation states that URDF represents only a subset of the model elements available through MJCF.
DECISION MATRIX
Portable robot model structure in the ROS ecosystem.
Native high-level modeling for MuJoCo dynamic systems.
Links are declared and connected by parent/child joints.
Bodies are nested directly; joints create degrees of freedom inside bodies.
Composite motion can require additional structure.
A body can contain multiple joints directly.
Limited to what URDF and extensions can represent.
Direct access to MuJoCo actuators, tendons, sensors, defaults and simulation options.
Consumed by ROS/tool-specific parsers.
MJCF is compiled into MuJoCo’s low-level mjModel.
Broad ROS ecosystem portability.
Optimized for MuJoCo fidelity and capabilities.
CHOOSE URDF
CHOOSE MJCF
USE BOTH
Maintain a portable URDF and compile/convert it into MJCF as the MuJoCo-specific derivative.
After conversion, treat MJCF-specific edits as additional simulator evidence rather than silently back-projecting them into URDF.
Preserve semantic identity and capabilities outside both formats when they exceed structural/simulation responsibilities.
PRIMARY SOURCES