Workflow:Google deepmind Mujoco Interactive simulation
| Knowledge Sources | |
|---|---|
| Domains | Robotics_Simulation, Physics_Engine, Visualization |
| Last Updated | 2026-02-15 04:30 GMT |
Overview
End-to-end process for loading a MuJoCo model and running an interactive real-time physics simulation with 3D visualization and mouse/keyboard control.
Description
This workflow covers the complete pipeline for launching an interactive MuJoCo simulation. It begins with loading a model from an MJCF XML or pre-compiled MJB binary file, allocating simulation state, initializing the OpenGL rendering pipeline, and entering a real-time loop that advances physics and renders frames at 60 FPS. The simulation supports interactive camera control via mouse (rotate, translate, zoom) and keyboard input for resetting state. This is the primary "Getting Started" workflow for MuJoCo.
Usage
Execute this workflow when you have an MJCF or URDF model file and want to interactively visualize and interact with a physics simulation in real time. This is the standard entry point for exploring MuJoCo models, debugging robot configurations, or demonstrating physics behavior.
Execution Steps
Step 1: Load_model
Load the physics model from an MJCF XML file or pre-compiled MJB binary. The XML compiler parses the MJCF specification, resolves mesh/texture assets, performs kinematic tree compilation, and produces the runtime mjModel structure containing all static model properties (body hierarchy, joint parameters, geometry, constraints).
Key considerations:
- MJCF is the native XML format; URDF is also supported via automatic conversion
- MJB is the pre-compiled binary format for faster loading (skip compilation)
- The compiler validates the model and reports errors with descriptive messages
- A Virtual File System (VFS) can be used for custom asset resolution
Step 2: Initialize_simulation_data
Allocate the mjData structure that holds the complete dynamic simulation state. This includes positions, velocities, forces, contacts, and all intermediate computation buffers. Optionally run a forward dynamics pass to initialize all derived quantities from the initial state.
Key considerations:
- mjData is preallocated based on the model's sizing parameters
- Memory is arena-allocated for cache-friendly access patterns
- Running mj_forward after allocation ensures all derived fields are consistent
- Multiple mjData instances can be created from one mjModel for parallel rollouts
Step 3: Initialize_visualization
Set up the visualization pipeline by initializing the abstract camera, rendering options, abstract scene, and GPU rendering context. The camera defines the viewpoint, options control what is rendered (contacts, forces, joints), the scene holds the geometry to be rendered, and the context manages OpenGL state.
Key considerations:
- Scene capacity (max geoms) must be sufficient for the model
- Font scale affects UI overlay text size
- The default free camera provides an orbital view centered on the model
- Visualization options can toggle display of contacts, constraints, and other debug info
Step 4: Create_window_and_register_callbacks
Initialize the GLFW windowing system, create an OpenGL window, and register input callbacks for keyboard, mouse button, mouse movement, and scroll events. These callbacks translate user input into camera movements and simulation control commands.
Key considerations:
- V-sync is typically enabled for smooth rendering
- Mouse callbacks map button+drag to camera rotate, translate, and zoom
- Keyboard callbacks handle simulation reset and other control actions
- Platform-specific considerations exist for macOS, Windows, and Linux
Step 5: Run_simulation_loop
Enter the main loop that runs until the window is closed. Each iteration advances the physics simulation in sub-steps to maintain real-time pacing, then updates the abstract scene from the simulation state and renders it to the framebuffer. The loop targets real-time simulation speed synchronized with the display refresh rate.
Key considerations:
- Physics sub-stepping ensures simulation time matches wall-clock time
- Scene update extracts renderable geometry from the current simulation state
- Rendering produces the final image in the framebuffer
- Buffer swap and event polling are blocking operations tied to V-sync
Step 6: Cleanup
Release all allocated resources in reverse order: free the abstract scene and rendering context, delete the simulation data and model, and terminate the windowing system. Proper cleanup prevents memory leaks and GPU resource exhaustion.
Key considerations:
- Resources must be freed in the correct order (scene before context)
- GLFW termination may crash on Linux with NVIDIA drivers (platform-specific workaround)
- mjModel and mjData must both be freed to avoid memory leaks