Migrate remaining legacy schema cfg call sites to fragments

[vidurv-nvidia]

Description

Migrates the remaining in-repo users of the legacy physics schema cfgs to schema fragments. These classes are deprecated in 3.1 and removed in 3.2 (#7839), so every site here currently emits DeprecationWarnings and would break at removal.

The earlier migration (#7838) converted source/ but never covered scripts/, and its grep missed the *BaseCfg spellings. On top of that, some new legacy usage has landed since. An AST scan (comments and docstrings excluded) finds 144 live legacy constructions or writer calls in 37 files on develop. This PR brings that to 0, outside the deliberate exclusions listed below.

Scope

• scripts/ (29 files): all tutorials, demos (including the MPM demos), convert_mesh / convert_instanceable, and three benchmarks.
• Task configs: core/reach/reach_env_cfg.py, contrib/ur10_particle_push, and one of the five contrib/nist sites.
• Tests: the camera-pose, first-frame-rendering and OpenCV-distortion sensor tests; the rigid/mass/collision parts of the cable and MPM tests; test_ovphysx_gravity.

Mapping rules

Every one of these has caused a real regression in an earlier migration:

• A bare fragment when one covers the fields. This keeps in-place tuning such as cfg.rigid_props.disable_gravity = True working downstream.
• Empty legacy cfgs map only to the core UsdPhysics* fragment. A fragment applies its schema even when all of its fields are None. RigidBodyPropertiesCfg() therefore becomes UsdPhysicsRigidBodyCfg() alone. Adding PhysxRigidBodyCfg() would add a PhysxRigidBodyAPI the legacy class never applied.
• enabled_self_collisions keeps its Newton mirror. The legacy writer also authors newton:selfCollisionEnabled, so these sites emit NewtonArticulationCfg next to PhysxArticulationCfg.
• disable_gravity goes to PhysxRigidBodyCfg, including on Newton-flavoured cfgs.
• define_* writer calls become apply_*(..., create_if_missing=True), which preserves creation.

Verification

USD-attribute parity at every site, with negative controls. Legacy and fragment forms are authored through the real spawners on sibling prims, and the harness diffs GetPrimTypeInfo().GetAppliedAPISchemas(), every authored attribute, and relationships.

• scripts/: 64 groups. 60 are identical. The other 4 differ only in that legacy authored physics:approximation="none" explicitly, while the fragment leaves it unset and it resolves to the same "none". 8 of 8 negative controls are flagged.
• source/: every site is identical, and every negative control is flagged.

Task configs are also checked end to end. Each task is loaded through its gym env_cfg_entry_point on both develop and this branch, across presets. All 22 affected spawned entities author identical USD, including the nist Franka on the real asset. A task-level negative control produces a diff.

Execution: 13 scripts ran headless for 100–300 steps with no schema deprecations: the tutorials, bin_packing, multi_asset, the sensor demos, and tacsl. convert_mesh was run end to end for 6 approximations. All 29 scripts compile. The migrated test files pass.

Not runnable in the dev environment, so covered by parity only: the Newton-physics script paths, including the MPM demos, which need a newer newton than was installed locally. Also the omni.replicator, ovrtx, and Haply scripts. CI covers the rest.

Deliberately left on the legacy API

• Spawner, converter, and schema routing internals. They are the legacy path, which must keep working until 3.2.
• Tests that exercise or compare the legacy path, such as test_schemas*, the parity tests, and the legacy arms of the fragment tests.
• integration_scene_cfgs.py. It is a backend-neutral core module, and its disable_gravity has no non-PhysX fragment home.
• Everything deformable. The deformable deprecation PR, stacked on Add volume and surface deformable schema fragment families #6673, handles it.
• 4 of the 5 contrib/nist sites. They nest a mesh-collision cfg inside collision_props. The deprecation messages point users to a spawner mesh_collision_props slot, but that slot exists only on MeshConverterCfg, not on UsdFileCfg or the shape and mesh spawners. There is no supported fragment path for these sites yet. That gap needs its own fix before 3.2.

Found along the way, not changed here

• RigidBodyMaterialCfg is deprecated too, and 8 scripts still use it.
• convert_instanceable.py's mesh branch is already broken on develop: it passes collision_approximation= to MeshConverterCfg, which raises TypeError.
• docs/source/how-to/write_articulation_cfg.rst still describes the legacy names.

Type of change

• Bug fix (non-breaking change which fixes an issue)

Release backport

• Backport this pull request to the active release branch after it merges into develop

Checklist

• I have read and understood the contribution guidelines
• I have run the pre-commit checks with ./isaaclab.sh --format
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• I have added a changelog fragment under source/<pkg>/changelog.d/ for every touched package
• I have added my name to the CONTRIBUTORS.md or my name already exists there

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge; no actionable regressions were established in the migrated schema configurations.

Summary

This PR migrates remaining scripts, task configurations, and tests from deprecated aggregate physics-schema configurations to composable schema fragments.

• Splits backend-neutral and backend-specific fields into the appropriate USD Physics, PhysX, Newton, and MuJoCo fragments.
• Preserves schema creation in custom spawners through fragment-family apply_* writers.
• Updates mesh conversion approximation routing and task-facing changelog documentation.
• Migrates affected test fixtures without changing their intended physics setup.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart LR
    A[Legacy aggregate schema cfg] --> B{Field ownership}
    B --> C[USD Physics fragment]
    B --> D[PhysX fragment]
    B --> E[Newton or MuJoCo fragment]
    C --> F[Spawner schema-family writer]
    D --> F
    E --> F
    F --> G[Apply core API if required]
    G --> H[Author backend-specific attributes]
    H --> I[Equivalent spawned USD physics configuration]

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_{Reviews (1) · Last reviewed commit: "Migrate test scene configs to schema fra..."}

[isaaclab-review-bot]

Isaac Lab Review Bot

The migration generally preserves legacy schema behavior across scripts, tasks, converters, and tests, but one Newton MPM bath-collider migration omits the core USD collision fragment that the legacy configuration applied.

• Design and architecture: The fragment split is otherwise applied consistently: bare fragments are used for single-schema ownership, lists combine core and backend fragments, explicit target mappings avoid creating physics on file-spawned visuals, and writer migrations preserve creation semantics. The bath-collider configuration is inconsistent with this pattern.
• API: No public API definition is removed or renamed. Task configuration slots that now contain multiple fragments have corresponding migration guidance explaining that callers must select the owning fragment before tuning its fields.
• Implementation: In newton_mpm_twoway_coupling.py, bath_collider replaces NewtonCollisionPropertiesCfg(contact_margin=...) with NewtonCollisionCfg alone. Comparable migrations in this patch pair NewtonCollisionCfg with UsdPhysicsCollisionCfg, so this site may stop authoring UsdPhysicsCollisionAPI and lose collider behavior. Add the core collision fragment alongside the Newton fragment.

Minor fixes needed. Posted 1 actionable finding inline.

Automated review; human maintainers own approval decisions.

[isaaclab-review-bot]

🟡 Warning · Implementation — Bath collider may lose core collision schema

Elsewhere in this diff the legacy Newton collision cfg maps to the core fragment plus the Newton one (line 207 maps an empty cfg to UsdPhysicsCollisionCfg(); granular and teapot_fill emit both). Here only NewtonCollisionCfg(contact_margin=...) is emitted, so the UsdPhysicsCollisionAPI the legacy class applied may no longer be authored, leaving the bath and chute panels without a collider. Pair it with UsdPhysicsCollisionCfg() as at the other sites.