Add runtime updates for MuJoCo contact pair custom attributes by adenzler-nvidia · Pull Request #1501 · newton-physics/newton

adenzler-nvidia · 2026-01-30T12:34:19Z

Summary

Adds support for runtime updates of MuJoCo contact pair (<pair>) custom attributes. Previously, pair properties were only set at model creation time. Now they can be dynamically modified during simulation via notify_model_changed(SolverNotifyFlags.SHAPE_PROPERTIES).

Changes

`kernels.py`

Added update_pair_properties_kernel that copies pair properties from Newton custom attributes to MuJoCo model arrays

`solver_mujoco.py`

Added update_pair_properties() method that launches the kernel when pair attributes are present
Uncommented pair fields in model_fields_to_expand for proper array tiling across worlds:
- pair_solref
- pair_solreffriction
- pair_solimp
- pair_margin
- pair_gap
- pair_friction
Called update_pair_properties() from notify_model_changed() under SHAPE_PROPERTIES flag

`test_mujoco_solver.py`

Added TestMuJoCoSolverPairProperties test class with multi-world test covering:
- Initial conversion from Newton to MuJoCo
- Runtime updates via notify_model_changed()
- Verification of all 6 randomizable pair attributes

Implementation Notes

Uses direct index computation (newton_pair = world * pairs_per_world + mjc_pair) instead of a mapping array, assuming pair ordering is consistent between Newton and MuJoCo
Only GPU (mujoco_warp) mode is supported; CPU mode returns early from update_pair_properties()

Before your PR is "Ready for review"

Necessary tests have been added and new examples are tested (see newton/tests/test_examples.py)
Documentation is up-to-date
Code passes formatting and linting checks with pre-commit run -a

Summary by CodeRabbit

New Features
- Runtime support for updating explicit contact pair solver properties (solver refs, friction, solver params, contact margins and gaps) so pair-level settings can be changed dynamically across multiple worlds and contact pairs.
Tests
- Added tests validating multi-world per-pair property propagation and runtime update behavior.

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- Add update_pair_properties_kernel to copy pair properties from Newton custom attributes to MuJoCo model arrays - Uncomment pair fields in model_fields_to_expand for tiling - Add update_pair_properties() method called under SHAPE_PROPERTIES flag - Supports: pair_solref, pair_solreffriction, pair_solimp, pair_margin, pair_gap, pair_friction

Tests initial conversion and runtime updates for all randomizable pair attributes: pair_solref, pair_solreffriction, pair_solimp, pair_margin, pair_gap, pair_friction across multiple worlds.

coderabbitai · 2026-01-30T12:35:00Z

Caution

Review failed

The head commit changed during the review from 550cf6f to 74d161f.

📝 Walkthrough

Walkthrough

Adds runtime propagation of per-pair contact solver properties from Newton model fields into the MuJoCo/Warp solver: a new Warp kernel performs per-world/per-pair copying, SolverMuJoCo gains an update method and is wired to call it on model-change notifications, and tests validate the behavior.

Changes

Cohort / File(s)	Summary
Kernel Implementation `newton/_src/solvers/mujoco/kernels.py`	Adds `update_pair_properties_kernel` Warp kernel that computes a global pair index per world and conditionally copies pair-level solver properties (solref, solreffriction, solimp, margin, gap, friction) from Newton input arrays into MuJoCo 2D output arrays.
Solver Integration `newton/_src/solvers/mujoco/solver_mujoco.py`	Adds `SolverMuJoCo.update_pair_properties()` method, imports the new kernel, expands model fields to include pair property arrays, and invokes the update method from `notify_model_changed()` when `SHAPE_PROPERTIES` is set; guarded for non-CPU and no-ops if inputs absent.
Test Suite `newton/tests/test_mujoco_solver.py`	Adds `TestMuJoCoSolverPairProperties::test_pair_properties_conversion_and_update()` validating multi-world/per-pair initial conversion and runtime updates for the six pair properties. Note: the test is duplicated within the file.

Sequence Diagram(s)

sequenceDiagram
  participant NewtonModel as Newton Model
  participant Solver as SolverMuJoCo
  participant Kernel as Warp Kernel
  participant MuJoCo as MuJoCo Model

  NewtonModel->>Solver: notify_model_changed(SHAPE_PROPERTIES)
  Solver->>Solver: compute pairs_per_world, counts
  Solver->>Kernel: launch update_pair_properties_kernel(inputs...)
  Kernel->>MuJoCo: write pair_solref/solreffriction/solimp/margin/gap/friction per world/pair
  Kernel-->>Solver: kernel complete
  Solver-->>NewtonModel: update complete

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

Move all SolverMuJoCo Warp kernels to kernels.py file #1027 #1040 — Adds a Warp kernel and wiring into SolverMuJoCo for per-pair property propagation (highly related).
Add parsing fixed tendons from MJCF #1406 — Adds per-world property-update kernels and SolverMuJoCo.update_* methods with notify_model_changed wiring (strongly related).

Suggested reviewers

eric-heiden
vreutskyy

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 77.78% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: adding runtime update support for MuJoCo contact pair attributes, which is the core functionality introduced across the kernels, solver, and tests.

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Signed-off-by: Alain Denzler <adenzler@nvidia.com>

- Add .copy() when capturing initial values to avoid view aliasing on CPU - Move .numpy() calls outside loop for performance - Use explicit wp.array() for assign statements with correct dtype/device

Signed-off-by: Alain Denzler <adenzler@nvidia.com>

vreutskyy

Looks good!

codecov · 2026-01-30T14:25:38Z

Codecov Report

❌ Patch coverage is 91.66667% with 2 lines in your changes missing coverage. Please review.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
newton/_src/solvers/mujoco/solver_mujoco.py	91.66%	2 Missing ⚠️

📢 Thoughts on this report? Let us know!

Signed-off-by: Alain Denzler <adenzler@nvidia.com>

add_body() creates the free joint and articulation internally, so no need for explicit add_joint_free() and add_articulation() calls.

…-physics#1501) Signed-off-by: Alain Denzler <adenzler@nvidia.com>

adenzler-nvidia added 2 commits January 30, 2026 13:27

Add tests for contact pair runtime property updates

22741a1

Tests initial conversion and runtime updates for all randomizable pair attributes: pair_solref, pair_solreffriction, pair_solimp, pair_margin, pair_gap, pair_friction across multiple worlds.

adenzler-nvidia requested a review from vreutskyy January 30, 2026 12:34

adenzler-nvidia added 2 commits January 30, 2026 14:15

assign warp arrays

29799ca

Signed-off-by: Alain Denzler <adenzler@nvidia.com>

Fix pair runtime update test for CPU mode

687db32

- Add .copy() when capturing initial values to avoid view aliasing on CPU - Move .numpy() calls outside loop for performance - Use explicit wp.array() for assign statements with correct dtype/device

adenzler-nvidia force-pushed the feature/pair-runtime-updates branch from c14cb91 to 687db32 Compare January 30, 2026 14:11

vreutskyy reviewed Jan 30, 2026

View reviewed changes

Comment thread newton/_src/solvers/mujoco/solver_mujoco.py Outdated

remove zero worlds check

fa0775e

Signed-off-by: Alain Denzler <adenzler@nvidia.com>

vreutskyy reviewed Jan 30, 2026

View reviewed changes

Comment thread newton/tests/test_mujoco_solver.py Outdated

vreutskyy previously approved these changes Jan 30, 2026

View reviewed changes

add body

87fb5d4

Signed-off-by: Alain Denzler <adenzler@nvidia.com>

adenzler-nvidia dismissed vreutskyy’s stale review via 87fb5d4 January 30, 2026 16:18

adenzler-nvidia added 2 commits January 30, 2026 17:18

Merge branch 'main' into feature/pair-runtime-updates

550cf6f

fix: use add_body() in pair properties test

74d161f

add_body() creates the free joint and articulation internally, so no need for explicit add_joint_free() and add_articulation() calls.

vreutskyy approved these changes Jan 30, 2026

View reviewed changes

adenzler-nvidia enabled auto-merge January 30, 2026 16:59

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

Merged via the queue into newton-physics:main with commit c96e4b9 Jan 30, 2026
22 checks passed

coderabbitai Bot mentioned this pull request Feb 20, 2026

Fix global pairs (world=-1) not exported to MuJoCo spec #1705

Merged

3 tasks

coderabbitai Bot mentioned this pull request Mar 30, 2026

Fix SolverMuJoCo NATIVECCD margin rejection #2260

Closed

3 tasks

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

Add runtime updates for MuJoCo contact pair custom attributes (newton…

fc5bffd

…-physics#1501) Signed-off-by: Alain Denzler <adenzler@nvidia.com>

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Add runtime updates for MuJoCo contact pair custom attributes#1501

Add runtime updates for MuJoCo contact pair custom attributes#1501
adenzler-nvidia merged 8 commits into
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adenzler-nvidia:feature/pair-runtime-updates

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adenzler-nvidia commented Jan 30, 2026 • edited by coderabbitai Bot Loading Uh oh! There was an error while loading. Please reload this page.

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Summary

Changes

kernels.py

solver_mujoco.py

test_mujoco_solver.py

Implementation Notes

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adenzler-nvidia commented Jan 30, 2026 •

edited by coderabbitai Bot

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`kernels.py`

`solver_mujoco.py`

`test_mujoco_solver.py`

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