Implementation:Google deepmind Mujoco mj makeData

Knowledge Sources	MuJoCo MuJoCo API Reference
Domains	Physics_Simulation, Memory_Management
Last Updated	2026-02-15 06:00 GMT

Overview

Concrete tool for allocating and initializing MuJoCo simulation state provided by the MuJoCo C API.

Description

The mj_makeData function allocates an mjData structure sized according to the given model, initializes plugins, and resets all state fields to the model's default configuration. The allocated structure uses arena-based memory management for efficient temporary allocation during simulation steps.

Usage

Call this function once per simulation thread after loading the model. The returned mjData pointer is the mutable workspace for all simulation computations.

Code Reference

Source Location

• Repository: mujoco
• File: src/engine/engine_io.c
• Lines: 1100-1108

Signature

mjData* mj_makeData(const mjModel* m);

Import

#include <mujoco/mujoco.h>

I/O Contract

Inputs

Name	Type	Required	Description
m	const mjModel*	Yes	Compiled model that determines allocation sizes

Outputs

Name	Type	Description
return	mjData*	Allocated and initialized simulation state (NULL on failure)

Usage Examples

#include <mujoco/mujoco.h>

// Load model
char error[1000];
mjModel* m = mj_loadXML("humanoid.xml", NULL, error, 1000);

// Allocate simulation state
mjData* d = mj_makeData(m);

// Simulation loop
for (int i = 0; i < 1000; i++) {
    mj_step(m, d);
}

// Cleanup
mj_deleteData(d);
mj_deleteModel(m);

Related Pages

Implements Principle

• Principle:Google_deepmind_Mujoco_Simulation_State_Initialization