New Validator

new-validator — Add a new performance validator rule

Creates a new usd-validation-nvidia rule class that wraps a Usd Optimize analysis-mode operation, registers it, tests it, and regenerates the docs.

The backing operation must already support analysis mode. If it doesn't, add executeAnalysisImpl() to the operation first (see PLUGINS.md § Analysis Mode).

What this skill covers

• How validators work — the base class, key class variables, and lifecycle.
• Step 1 — create the rule class.
• Step 2 — implement _CheckStage.
• Step 3 — add a fix suggestion (optional).
• Step 4 — add user-tunable parameters (optional).
• Step 5 — register the rule.
• Step 6 — add tests.
• Step 7 — build and verify.

Companion skills: new-operation (create the backing operation), run-validators (run the validator and apply fixes).

How validators work

All rule classes subclass BaseUsdOptimizeChecker from source/validators/python/usd_optimize/validators/base_usd_optimize_checker.py.

The base class handles running the operation in analysis mode via CheckStage(). It calls _AnalyzeStage() to execute the operation, then passes the analysis payload from the result to _CheckStage() — the one method every subclass must implement.

Key class variables:

Look at the existing checkers under source/validators/python/usd_optimize/validators/ as the primary reference. empty_leaf_checker.py is the simplest example; small_mesh_checker.py shows PARAMETERS; base_duplicate_geometry_checker.py shows a shared base class pattern.

Step 1 — Create the rule class

Create source/validators/python/usd_optimize/validators/<snake_case>_checker.py:

# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
# SPDX-License-Identifier: Apache-2.0

from pxr import Usd
from usd_validation_nvidia import capabilities, register_requirements

from .base_usd_optimize_checker import BaseUsdOptimizeChecker


@register_requirements(capabilities.<FamilyRequirements>.<RULE_ID>)
class <Name>Checker(BaseUsdOptimizeChecker):
    """
    One-sentence description of what this rule checks.
    """

    OPERATION_NAME: str = "<operation_key>"
    OPERATION_ARGS: dict = {"argName": value, ...}  # omit if no static args needed

    def _CheckStage(self, usdStage: Usd.Stage, analysis_data: dict):
        ...

@register_requirements binds the rule to an Asset Validator capability ID (from usd_validation_nvidia.capabilities). Pass override=True if overriding an existing base rule for the same capability.

Step 2 — Implement _CheckStage

analysis_data is the dict returned by the operation's analysis mode (the "analysis" key from the result). Its schema is specific to each operation — read the operation's executeAnalysisImpl() in the C++ source to see what it returns.

Call self._AddWarning() (most common) or self._AddFailedCheck() for each issue. The at argument takes a Usd.Stage or Usd.Prim:

def _CheckStage(self, usdStage: Usd.Stage, analysis_data: dict):
    count = len(analysis_data.get("someKey", []))
    if count > 0:
        self._AddWarning(
            message=f"Stage contains {count} problematic prims",
            at=usdStage.GetPrimAtPath("/"),
        )

To also report individual prim-level issues, iterate the paths and add a separate warning per prim with at=usdStage.GetPrimAtPath(path).

Step 3 — Add a fix suggestion (optional)

Rules that can auto-fix attach a Suggestion to the warning. The suggestion's callable receives (usdStage, at_prim) and applies the fix via analysis.optimize(). Use functools.partial to bind extra args:

from functools import partial
from usd_optimize.core import analysis
from usd_validation_nvidia import Suggestion

@classmethod
def _fix_stage(cls, usdStage: Usd.Stage, _: Usd.Prim) -> None:
    analysis.optimize(usdStage, [analysis.OperationConfig(cls.OPERATION_NAME, args=cls.OPERATION_ARGS)])

def _CheckStage(self, usdStage: Usd.Stage, analysis_data: dict):
    ...
    self._AddWarning(
        message="...",
        at=usdStage.GetPrimAtPath("/"),
        suggestion=Suggestion(
            message="Fix using Usd Optimize",
            callable=self._fix_stage,
        ),
    )

When the fix should use the operation configs derived from the analysis result (rather than static args), use self.suggested_operations — it is populated by _AnalyzeStage before _CheckStage is called. See small_mesh_checker.py and zero_extent_checker.py for this pattern:

suggestion=Suggestion(
    message="Fix using Usd Optimize",
    callable=partial(self._fix_stage, operation_configs=self.suggested_operations),
)

Step 4 — Add user-tunable parameters (optional)

Declare PARAMETERS to expose per-rule settings in Asset Validator's parameter UI. Each entry maps a display name to a Parameter that names the underlying operation arg and its default:

from .base_usd_optimize_checker import BaseUsdOptimizeChecker, Parameter, ParameterFromOpArg

class MyChecker(BaseUsdOptimizeChecker):
    PARAMETERS = {
        "SIZE_THRESHOLD": Parameter(op_arg="threshold", default=0.001,
                                    description="Minimum size before a mesh is flagged."),
    }

Use ParameterFromOpArg instead of Parameter to pull the default and description directly from the operation's argument metadata (avoids duplication):

    PARAMETERS = {
        "SIZE_THRESHOLD": ParameterFromOpArg("threshold"),
    }

In _CheckStage, read the effective value (with any user override applied) via self._effective_args()["threshold"] rather than OPERATION_ARGS directly.

Step 5 — Register the rule

In source/validators/python/usd_optimize/validators/__init__.py:

1. Add an import at the top:

   from .<snake_case>_checker import <Name>Checker
   

2. Add to _RULE_CATEGORIES:

   (<Name>Checker, "Usd:Performance"),   # or "Omni:Geometry"
   

   Use "Usd:Performance" for stage/scene-level conditions; "Omni:Geometry" for low-level geometric defects.
3. Add to __all__.

Step 6 — Add tests

Add test cases for the new rule to the existing test files in source/tests/test.python/:

• test_checkers.py — functional tests using ValidationTestCaseMixin.assertRule(). Add a test method that supplies a .usda fixture and asserts the expected warnings. Add the required fixtures to the test data directory.
• test_validator_plugin_entry_point.py — no changes needed; it imports from _RULE_CATEGORIES and covers all registered rules automatically.
• test_checker_parameters.py — add a test only if the rule declares PARAMETERS and has non-trivial parameter logic to verify.

Step 7 — Build and verify

./repo.sh build
./repo.sh test -s python
./repo.sh docs_gen --autogen_only

After docs_gen, the rule appears in docs/performance-validators.rst.

Verify the rule is registered:

from usd_optimize.validators import register_all
rules = register_all()
assert any(r.__name__ == "<Name>Checker" for r in rules)