Fix Pink IK USD-to-URDF conversion on aarch64 (#6177)

[kellyguo11]

Description

• Remove the Pink IK runtime dependency on nvidia.srl and use Isaac Sim's built-in isaacsim.asset.exporter.urdf converter.

• Normalize generated URDF joint limits so Pinocchio accepts Isaac Sim exporter output (effort/velocity defaults and inf cleanup).

• Align affected GR1T2 and G1-Inspire Pink IK frame names with the link/frame names produced by the Isaac Sim exporter.

• Remove the nvidia-srl-usd-to-urdf dependency from isaaclab_mimic.

• python -m py_compile docs/conf.py source/isaaclab/isaaclab/controllers/utils.py source/isaaclab/test/controllers/test_controller_utils.py source/isaaclab_tasks/isaaclab_tasks/contrib/pick_place/nutpour_gr1t2_pink_ik_env_cfg.py source/isaaclab_tasks/isaaclab_tasks/contrib/pick_place/exhaustpipe_gr1t2_pink_ik_env_cfg.py source/isaaclab_tasks/isaaclab_tasks/contrib/pick_place/pickplace_gr1t2_env_cfg.py source/isaaclab_tasks/isaaclab_tasks/contrib/pick_place/pickplace_unitree_g1_inspire_hand_env_cfg.py

• git diff --check

• Direct mocked smoke test of convert_usd_to_urdf() using Isaac Sim exporter modules.

• Generated GR1T2 and G1-Inspire URDFs with isaacsim.asset.exporter.urdf, sanitized them with the new utility, and verified Pinocchio can load them and contains the adjusted target frames:

  • GR1T2_fourier_hand_6dof.urdf nq 54 nv 54 missing frames []
  • g1_29dof_inspire_hand.urdf nq 53 nv 53 missing frames []

• Attempted focused pytest through ./isaaclab.sh -p -m pytest source/isaaclab/test/controllers/test_controller_utils.py -k convert_usd_to_urdf_uses_isaacsim_exporter -q, but this worktree uses system Python and is missing lazy_loader.

• Attempted Ruff on touched files, but no local Python environment had Ruff installed.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (existing functionality will not work without user modification)
• Documentation update

Screenshots

Please attach before and after screenshots of the change if applicable.

Checklist

• I have read and understood the contribution guidelines
• I have run the pre-commit checks with ./isaaclab.sh --format
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• I have updated the changelog and the corresponding version in the extension's config/extension.toml file
• I have added my name to the CONTRIBUTORS.md or my name already exists there

[greptile-apps]

Greptile Summary

This PR fixes the Pink IK USD-to-URDF pipeline on aarch64 by replacing the unavailable nvidia.srl package with Isaac Sim's built-in isaacsim.asset.exporter.urdf converter, then surgically sanitizing only the effort/velocity joint-limit attributes that Pinocchio requires to be finite (the old approach replaced all "inf" substrings globally, which also corrupted lower/upper position limits).

• Core converter swap (utils.py): UsdToUrdfConverter is now imported lazily inside the conversion block; _sanitize_urdf_for_pinocchio uses xml.etree.ElementTree to patch only non-kinematic limit fields instead of a blanket string replace that would zero out position limits.
• Dependency cleanup: nvidia-srl-usd-to-urdf removed from isaaclab_mimic/setup.py; nvidia.srl removed from docs/conf.py mock imports; usd-core pin loosened from ==25.11.0 to >=25.11,<26.0 for ARM64 compatibility.
• Frame name alignment: GR1T2 and G1-Inspire task configs updated to use the un-prefixed link names emitted by the Isaac Sim exporter (e.g. left_hand_pitch_link instead of GR1T2_fourier_hand_6dof_left_hand_pitch_link).

Confidence Score: 4/5

Safe to merge; the changes are well-scoped and tested, with one cosmetic concern around XML comment preservation during URDF sanitization.

The converter swap and sanitization logic are straightforward and backed by a mocked smoke test. The only notable gap is that xml.etree.ElementTree silently drops comments when rewriting the URDF, but Isaac Sim's exporter output is effectively comment-free, so this has no runtime impact today.

source/isaaclab/isaaclab/controllers/utils.py — specifically the _sanitize_urdf_for_pinocchio rewrite path

Important Files Changed

Filename	Overview
source/isaaclab/isaaclab/controllers/utils.py	Replaces nvidia.srl converter with isaacsim.asset.exporter.urdf; adds _sanitize_urdf_for_pinocchio using ElementTree — comments and XML declaration are silently dropped on rewrite
source/isaaclab/test/controllers/test_controller_utils.py	Adds mocked smoke test for the new convert_usd_to_urdf path; correctly validates extension, converter args, return paths, and sanitized limit attributes
source/isaaclab/setup.py	Loosens usd-core from ==25.11.0 to >=25.11,<26.0; intentional for aarch64 compatibility but broadens the version range allowed
source/isaaclab_mimic/setup.py	Removes nvidia-srl-usd-to-urdf dependency (and its aarch64 guard), cleanly eliminating the broken dependency
source/isaaclab_tasks/isaaclab_tasks/manager_based/manipulation/pick_place/pickplace_gr1t2_env_cfg.py	Frame names updated from GR1T2_fourier_hand_6dof_* prefix to bare link names matching Isaac Sim exporter output
source/isaaclab_tasks/isaaclab_tasks/manager_based/manipulation/pick_place/pickplace_unitree_g1_inspire_hand_env_cfg.py	Frame names updated from g1_29dof_rev_1_0_* prefix to bare link names matching Isaac Sim exporter output

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["convert_usd_to_urdf(usd_path, output_path)"] --> B["enable_extension(isaacsim.asset.exporter.urdf)"]
    B --> C{URDF & meshes exist\nand not force_conversion?}
    C -->|Skip| Z["return urdf_output_path, urdf_meshes_output_dir"]
    C -->|Convert| D["makedirs urdf/ and meshes/"]
    D --> E["UsdToUrdfConverter(stage, mesh_dir_name='../meshes', ...)"]
    E --> F["usd_to_urdf.convert(urdf_output_path)"]
    F --> G["_sanitize_urdf_for_pinocchio(urdf_output_path)"]
    G --> H["ET.parse(urdf_path)"]
    H --> I{"effort / velocity\n== inf or None?"}
    I -->|Yes| J["Set attr to '0.'"]
    J --> K{"changed?"}
    I -->|No| K
    K -->|Yes| L["tree.write(urdf_path, encoding='unicode')"]
    K -->|No| Z
    L --> Z

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_{Reviews (1): Last reviewed commit: "Fix Pink IK USD-to-URDF conversion on aa..." | Re-trigger Greptile}

[greptile-apps]

xml.etree.ElementTree silently drops XML comments during parsing. When changed=True, the rewritten file will lose any comments that the Isaac Sim exporter included. While current exporter output appears comment-free, this is a fragile assumption. In Python 3.8+, ET.XMLParser(target=ET.TreeBuilder(insert_comments=True)) preserves comments. Additionally, tree.write(..., encoding="unicode") omits the XML declaration from the original file.

Suggested change

	def _sanitize_urdf_for_pinocchio(urdf_path: str) -> None:
	"""Fill Pinocchio-required non-kinematic joint-limit fields in exported URDFs."""
	tree = ET.parse(urdf_path)
	changed = False
	for limit in tree.iter("limit"):
	for attr in ("effort", "velocity"):
	if limit.get(attr) in {None, "inf", "+inf", "-inf"}:
	limit.set(attr, "0.")
	changed = True
	if changed:
	tree.write(urdf_path, encoding="unicode")
	def _sanitize_urdf_for_pinocchio(urdf_path: str) -> None:
	"""Fill Pinocchio-required non-kinematic joint-limit fields in exported URDFs."""
	parser = ET.XMLParser(target=ET.TreeBuilder(insert_comments=True))
	tree = ET.parse(urdf_path, parser=parser)
	changed = False
	for limit in tree.iter("limit"):
	for attr in ("effort", "velocity"):
	if limit.get(attr) in {None, "inf", "+inf", "-inf"}:
	limit.set(attr, "0.")
	changed = True
	if changed:
	tree.write(urdf_path, encoding="unicode", xml_declaration=False)

Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!