Workflow:Google deepmind Mujoco Model compilation and conversion
| Knowledge Sources | |
|---|---|
| Domains | Robotics_Simulation, Model_Processing, Physics_Engine |
| Last Updated | 2026-02-15 04:30 GMT |
Overview
End-to-end process for compiling MuJoCo model files from MJCF XML or URDF format and converting between supported output formats (MJCF, MJB binary, TXT text dump).
Description
This workflow covers the model compilation pipeline that transforms human-readable MJCF XML or URDF robot descriptions into the runtime mjModel structure. MuJoCo's compiler parses the XML specification, resolves external assets (meshes, textures, heightfields), processes composite and deformable bodies, computes kinematic trees, and produces optimized runtime data structures. The compiled model can be saved to MJB binary format for faster subsequent loading, exported back to MJCF XML, or printed as a human-readable TXT dump for inspection. The workflow also supports measuring compilation time with caching.
Usage
Execute this workflow when you need to validate an MJCF or URDF model file, convert between model formats for deployment, generate a pre-compiled MJB binary for faster loading in production, or inspect the compiled model structure as text output.
Execution Steps
Step 1: Determine_file_formats
Identify the input and output file formats based on file extensions. The input can be MJCF XML (.xml), URDF (.urdf), or pre-compiled MJB binary (.mjb). The output can be MJCF XML (.xml), MJB binary (.mjb), TXT text dump (.txt), or omitted entirely for timing-only compilation. Not all format combinations are valid (e.g., MJB to XML conversion is not supported).
Key considerations:
- File extension determines the format (case-insensitive)
- URDF input is automatically converted through the URDF-to-MJCF parser
- MJB-to-XML conversion is not supported (one-way compilation)
- Omitting the output file runs compilation twice to measure caching impact
Step 2: Load_and_compile_model
Parse and compile the input model file into the runtime mjModel structure. For XML/URDF inputs, the compiler performs full parsing, asset resolution, kinematic tree construction, inertia computation, and constraint setup. For MJB inputs, the binary is deserialized directly. Compilation time is measured for performance analysis.
Key considerations:
- XML compilation involves multiple passes: parsing, resolving, compiling
- Asset resolution uses the Virtual File System (VFS) or filesystem paths
- The compiler reports detailed error messages with element and attribute context
- Second compilation is faster due to asset caching (mesh, texture reuse)
Step 3: Validate_compilation
Verify that the compilation succeeded by checking the returned model pointer. If compilation fails, the error message provides specific information about the XML element or attribute that caused the failure. This enables iterative model development with rapid feedback.
Key considerations:
- Error messages include the XML path and attribute name
- Common errors: missing assets, invalid joint configurations, self-collision
- Warnings are issued for non-fatal issues (e.g., unused references)
Step 4: Save_or_export_model
Write the compiled model to the specified output format. MJB binary output produces a compact, fast-loading file. MJCF XML output regenerates the XML specification from the compiled model. TXT output prints a human-readable dump of all model constants, sizes, and parameters for inspection and debugging.
Key considerations:
- MJB format preserves all compiled data for byte-exact reconstruction
- XML export may differ from the original input due to compiler normalization
- TXT output is useful for debugging model structure and comparing versions
- Output file overwrite requires explicit confirmation
Step 5: Report_compilation_metrics
Display compilation timing results, including first-pass and second-pass times when running in timing mode. The second compilation demonstrates the effect of asset caching, which significantly reduces load time for models with large meshes or textures.
Key considerations:
- First compilation includes all asset processing (mesh loading, convex hull, etc.)
- Second compilation benefits from cached assets
- Cache speedup is most significant for models with complex meshes
- Timing data helps identify compilation bottlenecks