Implementation:Haosulab ManiSkill URDFLoader

Knowledge Sources	Haosulab_ManiSkill
Domains	Robotics, Simulation, Model Loading
Last Updated	2026-02-15 08:00 GMT

Overview

Concrete tool for loading URDF (Unified Robot Description Format) files into ManiSkill with support for parallel environment building.

Description

The urdf_loader.py module provides the public URDFLoader class, which extends SAPIEN's URDFLoader with ManiSkill-specific parallelization, naming, and camera extraction support.

URDFLoader extends SapienURDFLoader with:

scene -- ManiSkillScene reference for parallel building.
name -- Base name for loaded articulations and actors.
disable_self_collisions -- Flag to disable self-collision between links.

parse() method:

Calls the parent URDF parser to get articulation/actor builders and cameras.
Assigns names based on the loader's name attribute.
Optionally disables self-collisions via collision group bit manipulation.
Returns a ParsedURDFData TypedDict.

load() method:

Parses the URDF, validates that only one articulation exists (throws exception for multi-object URDFs), builds across specified sub-scenes, and returns a single Articulation.
Handles camera definitions embedded in the URDF by creating RenderCameraComponent instances and mounting them on the appropriate entities.

load_file_as_articulation_builder() -- Returns the raw ArticulationBuilder without building.

Usage

Primary interface for loading URDF robot models into ManiSkill environments. Used by robot agent classes during environment initialization.

Code Reference

Source Location

Repository: Haosulab_ManiSkill
File: mani_skill/utils/building/urdf_loader.py

Signature

class ParsedURDFData(TypedDict):
    articulation_builders: list[ArticulationBuilder]
    actor_builders: list[ActorBuilder]
    cameras: list[Any]

class URDFLoader(SapienURDFLoader):
    scene: ManiSkillScene
    name: str = None
    disable_self_collisions: bool = False

    def parse(self, urdf_file, srdf_file=None, package_dir=None) -> ParsedURDFData: ...
    def load(self, urdf_file, srdf_file=None, package_dir=None, name=None, scene_idxs=None) -> Articulation: ...
    def load_file_as_articulation_builder(self, urdf_file, srdf_file=None, package_dir=None) -> ArticulationBuilder: ...

Import

from mani_skill.utils.building.urdf_loader import URDFLoader

I/O Contract

Inputs

Name	Type	Required	Description
urdf_file	str	Yes	Path to the URDF file
srdf_file	str	No	SRDF file (defaults to .srdf alongside URDF)
package_dir	str	No	Base directory for resolving "package://" paths
name	str	No	Name for the loaded articulation
scene_idxs	list[int]	No	Sub-scene indices to build in

Outputs

Name	Type	Description
Articulation	Articulation	The loaded articulation

Usage Examples

Basic Usage

from mani_skill.utils.building.urdf_loader import URDFLoader

loader = URDFLoader()
loader.scene = env.scene
loader.name = "panda"

articulation = loader.load(
    "franka_description/panda.urdf",
    package_dir="franka_description/"
)

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