fix: add class default inheritance for actuator parsing in MJCF by adenzler-nvidia · Pull Request #1503 · newton-physics/newton

adenzler-nvidia · 2026-01-30T15:05:37Z

Actuator elements (, , etc.) now properly inherit attributes like biasprm, gainprm, ctrlrange from their default class. This fixes parsing of menagerie robots like UR5e that rely on class defaults for actuator configuration.

Changes:

Use merge_attrib to combine class defaults with element attributes
Apply all defaults first, then class-specific defaults, then element attributes

Add tests for class default inheritance in actuator parsing.

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Necessary tests have been added and new examples are tested (see newton/tests/test_examples.py)
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Summary by CodeRabbit

Bug Fixes
- Improved actuator parameter inheritance from default classes in MuJoCo MJCF files, ensuring proper attribute resolution for actuator gains, limits, and bias parameters.
Tests
- Added comprehensive test coverage for actuator default class inheritance scenarios.

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Actuator elements (<general>, <position>, etc.) now properly inherit attributes like biasprm, gainprm, ctrlrange from their default class. This fixes parsing of menagerie robots like UR5e that rely on class defaults for actuator configuration. Changes: - Use merge_attrib to combine class defaults with element attributes - Apply __all__ defaults first, then class-specific defaults, then element attributes Add tests for class default inheritance in actuator parsing.

coderabbitai · 2026-01-30T15:05:51Z

📝 Walkthrough

Walkthrough

Centralizes attribute resolution for actuators by merging class-based defaults with element-specific attributes before use. Modified the parse_actuators function to derive target names and parameters from merged attributes rather than raw element attributes. Added comprehensive test coverage for class inheritance behavior.

Changes

Cohort / File(s)	Summary
Actuator Attribute Resolution `newton/_src/utils/import_mjcf.py`	Refactored actuator parsing to compute merged_attrib by combining global defaults, class-specific defaults, and element attributes. Updated all actuator attribute reads (joint/body/tendon targets, kp/kv parameters, actuation name) to use merged_attrib instead of raw element attributes.
Test Coverage `newton/tests/test_import_mjcf.py`	Added TestMjcfActuatorClassDefaults test class with three tests verifying that general and position actuators properly inherit biasprm, gainprm, and kp parameters from MuJoCo default classes.

Sequence Diagram

sequenceDiagram
    participant Parser as MJCF Parser
    participant Defaults as Class Defaults Resolver
    participant Merge as Attribute Merger
    participant ActParse as Actuator Parser
    participant Model as Model Builder

    Parser->>Defaults: Request class defaults hierarchy
    Defaults-->>Parser: Return resolved class defaults (with inheritance)
    
    Parser->>ActParse: Begin parsing actuator element
    ActParse->>Merge: Element attributes + class defaults
    Merge->>Merge: Combine global defaults<br/>+ class defaults<br/>+ element attributes
    Merge-->>ActParse: Return merged_attrib
    
    ActParse->>ActParse: Derive target (joint/body/tendon)<br/>from merged_attrib
    ActParse->>ActParse: Extract kp, kv, actuation name<br/>from merged_attrib
    ActParse->>ActParse: Parse custom attributes<br/>using merged_attrib
    ActParse-->>Model: Finalized actuator with<br/>inherited parameters

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~22 minutes

Possibly related PRs

PR #1207: Adds recursive resolve_defaults step that propagates parent defaults; this PR depends on that infrastructure to merge class defaults into actuator attributes.
PR #1170: Modifies the same MJCF actuator parsing logic in import_mjcf.py to handle per-DOF effort_limit and actuatorfrcrange, directly overlapping with the implementation area.

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The pull request title accurately describes the main change: adding class default inheritance for actuator parsing in MJCF format.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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codecov · 2026-01-30T15:15:10Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

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…on-physics#1503)

adenzler-nvidia requested a review from jvonmuralt January 30, 2026 15:05

jvonmuralt approved these changes Jan 30, 2026

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adenzler-nvidia added this pull request to the merge queue Jan 30, 2026

github-merge-queue Bot removed this pull request from the merge queue due to failed status checks Jan 30, 2026

adenzler-nvidia added this pull request to the merge queue Jan 30, 2026

Merged via the queue into newton-physics:main with commit f4dd140 Jan 30, 2026
22 checks passed

This was referenced Feb 5, 2026

MJCF import: auto-enable actuator *limited flags when *range is specified in MJCF #1504

Merged

Verify default class and value handling #1556

Merged

This was referenced Feb 18, 2026

Fix implicit biastype for position/velocity actuator shortcuts #1678

Merged

Support dampratio for position/velocity actuator shortcuts #1722

Merged

Resolve inheritrange for position actuators in MJCF parser #1727

Merged

coderabbitai Bot mentioned this pull request Feb 25, 2026

Fix default kp/kv for position and velocity actuators #1786

Merged

3 tasks

coderabbitai Bot mentioned this pull request Mar 11, 2026

Fix MJCF mesh scale resolved from geom class instead of asset class #2057

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coderabbitai Bot mentioned this pull request Mar 25, 2026

Add site-targeted actuator support to MuJoCo solver #2220

Merged

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mmacklin pushed a commit to mmacklin/newton that referenced this pull request Apr 7, 2026

fix: add class default inheritance for actuator parsing in MJCF (newt…

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fix: add class default inheritance for actuator parsing in MJCF#1503

fix: add class default inheritance for actuator parsing in MJCF#1503
adenzler-nvidia merged 1 commit into
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adenzler-nvidia:fix/mjcf-actuator-class-defaults

adenzler-nvidia commented Jan 30, 2026 •

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