Implementation:Google deepmind Dm control MuJoCo Assets Export

Knowledge Sources	Google_deepmind_Dm_control
Domains	Blender, MuJoCo, Export
Last Updated	2026-02-15 04:00 GMT

Overview

The mujoco_assets module handles the export of Blender mesh geometry and material definitions into MuJoCo-compatible asset representations, including binary .msh mesh files and XML asset elements.

Description

The MujocoMesh class extracts vertices, normals, UV coordinates, and face indices from a Blender mesh filtered by material index, enabling per-material mesh splitting. MuJoCo requires single-material-per-mesh, so a Blender mesh with multiple materials is split into separate MujocoMesh instances. For two-sided materials (where backface culling is disabled), geometry is duplicated with flipped normals and reversed winding order.

The save() method serializes mesh data into MuJoCo's binary .msh format using struct.pack with a header of 4 integers (vertex count, normal count, texcoord count, face count) followed by float arrays for vertex positions, normals, UV coordinates, and integer face indices.

mesh_asset_builder() creates XML <mesh> elements for each valid material-mesh pair. material_asset_builder() converts Blender material properties (diffuse color, specular intensity, roughness, metallic) to MuJoCo material XML attributes, inverting roughness to shininess and mapping metallic to reflectance. The top-level export_to_xml() iterates over all scene objects, deduplicates meshes and materials, optionally applies mesh modifiers, and assembles the complete <asset> XML element.

Usage

Called by the Blender Exporter addon's _export_mjcf method. Not typically used directly, but rather as part of the Blender-to-MuJoCo export pipeline.

Code Reference

Source Location

• Repository: Google_deepmind_Dm_control
• File: dm_control/blender/mujoco_exporter/mujoco_assets.py
• Lines: 1-175

Signature

class MujocoMesh:
    def __init__(self, mesh: bpy.types.Mesh, material_idx: int, two_sided: bool):
    def save(self, filepath: str) -> None:

def mesh_asset_builder(
    doc: minidom.Document,
    mesh: bpy.types.Mesh,
    materials: Sequence[bpy.types.Material],
    folder: str,
) -> Sequence[minidom.Element]:

def clip01(value):

def material_asset_builder(
    doc: minidom.Document, mat: bpy.types.Material
) -> minidom.Element:

def export_to_xml(
    doc: minidom.Document,
    objects: Sequence[blender_scene.ObjectRef],
    folder: str,
    apply_mesh_modifiers: bool,
) -> minidom.Element:

Import

from dm_control.blender.mujoco_exporter import mujoco_assets

I/O Contract

Inputs

Name	Type	Required	Description
doc	minidom.Document	Yes	XML document used for creating elements
objects	Sequence[ObjectRef]	Yes	List of Blender scene objects to export
folder	str	Yes	Output directory for mesh .msh files
apply_mesh_modifiers	bool	Yes	Whether to apply Blender mesh modifiers before export

Outputs

Name	Type	Description
return	minidom.Element	An <asset> XML element containing <mesh> and <material> children
.msh files	binary files	Binary mesh files written to the output folder

Usage Examples

from xml.dom import minidom
from dm_control.blender.mujoco_exporter import mujoco_assets

xml_doc = minidom.Document()

# Export all assets from visible Blender objects
asset_el = mujoco_assets.export_to_xml(
    doc=xml_doc,
    objects=blender_objects,
    folder='/path/to/output/',
    apply_mesh_modifiers=True,
)

# The asset_el contains <mesh> and <material> XML children
mujoco_root.appendChild(asset_el)