Implementation:ARISE Initiative Robosuite XmlObjects

Knowledge Sources	ARISE_Initiative_Robosuite
Domains	Robotics, Simulation, MJCF_Modeling
Last Updated	2026-02-15 07:00 GMT

Overview

The xml_objects module provides a collection of concrete MujocoXMLObject subclasses that load pre-defined simulation objects from MJCF XML files, including everyday items, task-specific objects, and visual fiducial markers.

Description

This module contains 15 ready-to-use object classes that wrap MJCF XML model files. Each class extends MujocoXMLObject and specifies its corresponding XML file path (resolved via xml_path_completion()), default joint configuration, geom type, and collision geom duplication settings.

The physical objects include: BottleObject, CanObject (coke can for PickPlace), LemonObject, MilkObject (milk carton for PickPlace), BreadObject (bread loaf for PickPlace), CerealObject (cereal box for PickPlace), SquareNutObject (for NutAssembly), RoundNutObject (for NutAssembly), PlateWithHoleObject (for PegInHole), and DoorObject (for Door task). Most physical objects use a free joint with a small damping value (0.0005), while PlateWithHoleObject and DoorObject have no top-level joints since they are fixed in their respective tasks.

Visual fiducial objects include MilkVisualObject, BreadVisualObject, CerealVisualObject, and CanVisualObject. These are visual-only (no physics) objects with no joints, used in the PickPlace task as goal position indicators. They are created with obj_type="visual" and joints=None.

The DoorObject is the most complex class, supporting configurable friction and damping parameters that are applied directly to the hinge joint in the XML. It also supports a lock variant that loads a different XML file, and exposes named body references (door_body, frame_body, latch_body) and a hinge joint name. Both SquareNutObject and RoundNutObject override important_sites to include a "handle" site for nut placement detection. DoorObject similarly adds a "handle" important site.

Usage

Use these classes to instantiate standard robosuite task objects. They are the primary objects used in built-in tasks like PickPlace, NutAssembly, PegInHole, and Door. Use the visual fiducial variants as goal markers that do not participate in physics simulation.

Code Reference

Source Location

Repository: ARISE_Initiative_Robosuite
File: robosuite/models/objects/xml_objects.py

Signature

class BottleObject(MujocoXMLObject):
    def __init__(self, name)

class CanObject(MujocoXMLObject):
    def __init__(self, name)

class LemonObject(MujocoXMLObject):
    def __init__(self, name)

class MilkObject(MujocoXMLObject):
    def __init__(self, name)

class BreadObject(MujocoXMLObject):
    def __init__(self, name)

class CerealObject(MujocoXMLObject):
    def __init__(self, name)

class SquareNutObject(MujocoXMLObject):
    def __init__(self, name)

class RoundNutObject(MujocoXMLObject):
    def __init__(self, name)

class PlateWithHoleObject(MujocoXMLObject):
    def __init__(self, name)

class DoorObject(MujocoXMLObject):
    def __init__(self, name, friction=None, damping=None, lock=False)

# Visual fiducial objects:
class MilkVisualObject(MujocoXMLObject):
    def __init__(self, name)

class BreadVisualObject(MujocoXMLObject):
    def __init__(self, name)

class CerealVisualObject(MujocoXMLObject):
    def __init__(self, name)

class CanVisualObject(MujocoXMLObject):
    def __init__(self, name)

Import

from robosuite.models.objects.xml_objects import (
    BottleObject, CanObject, LemonObject, MilkObject,
    BreadObject, CerealObject, SquareNutObject, RoundNutObject,
    PlateWithHoleObject, DoorObject,
    MilkVisualObject, BreadVisualObject, CerealVisualObject, CanVisualObject,
)

I/O Contract

Inputs

Name	Type	Required	Description
name	str	Yes	Unique name for this object instance

Inputs (DoorObject additional)

Name	Type	Required	Description
friction	3-tuple of float or None	No	Friction parameters to override the XML-defined hinge friction
damping	float or None	No	Damping parameter to override the XML-defined hinge damping
lock	bool	No	If True, loads the locked door variant. Default: False

Outputs

Name	Type	Description
root_body	str	Prefix-corrected root body name
contact_geoms	list of str	Collision geom names
visual_geoms	list of str	Visual geom names
important_sites	dict	Task-relevant sites. SquareNutObject and RoundNutObject include "handle" site. DoorObject includes "handle" site.
bottom_offset	np.array	From bottom_site in the XML
top_offset	np.array	From top_site in the XML
horizontal_radius	float	From horizontal_radius_site in the XML

Usage Examples

from robosuite.models.objects.xml_objects import CanObject, DoorObject, CanVisualObject

# Create a can object
can = CanObject(name="soda_can")
can_xml = can.get_obj()
print(can.root_body)         # "soda_can_main"
print(can.contact_geoms)     # collision geoms

# Create a door with custom friction
door = DoorObject(name="front_door", friction=0.5, damping=0.1, lock=True)
print(door.door_body)        # "front_door_door"
print(door.hinge_joint)      # "front_door_hinge"
print(door.important_sites)  # includes "handle" key

# Create a visual-only can as a goal marker
can_goal = CanVisualObject(name="can_goal")
# This object has no physics, only visual rendering

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