Rules

Basic

class omni.asset_validator.core.ByteAlignmentChecker: Files within a usdz package must be laid out properly, i.e. they should be aligned to 64 bytes.

class omni.asset_validator.core.CompressionChecker: Files within a usdz package should not be compressed or encrypted.

class omni.asset_validator.core.MissingReferenceChecker: The composed USD stage should not contain any unresolvable asset dependencies (in every possible variation of the asset), when using the default asset resolver.

class omni.asset_validator.core.StageMetadataChecker: All stages should declare their ‘upAxis’ and ‘metersPerUnit’. Stages that can be consumed as referencable assets should furthermore have a valid ‘defaultPrim’ declared, and stages meant for consumer-level packaging should always have upAxis set to ‘Y’

class omni.asset_validator.core.TextureChecker

A RuleChecker which handles locating texture files automatically.

Texture files should be readable by intended client (only .jpg or .png for consumer-level USDZ). Derived classes can reimplement TextureChecker._CheckTexture.

class omni.asset_validator.core.PrimEncapsulationChecker

Check for basic prim encapsulation rules:

Boundables may not be nested under Gprims
Connectable prims (e.g. Shader, Material, etc) can only be nested inside other Container-like Connectable prims. Container-like prims include Material, NodeGraph, Light, LightFilter, and exclude Shader

class omni.asset_validator.core.NormalMapTextureChecker

UsdUVTexture nodes that feed the inputs:normals of a UsdPreviewSurface must ensure that the data is encoded and scaled properly. Specifically:

Since normals are expected to be in the range [(-1,-1,-1), (1,1,1)], the Texture node must transform 8-bit textures from their [0..1] range by setting its inputs:scale to [2, 2, 2, 1] and inputs:bias to [-1, -1, -1, 0]

Normal map data is commonly expected to be linearly encoded. However, many image-writing tools automatically set the profile of three-channel, 8-bit images to SRGB. To prevent an unwanted transformation, the UsdUVTexture’s inputs:sourceColorSpace must be set to “raw”. This program cannot currently read the texture metadata itself, so for now we emit warnings about this potential infraction for all 8 bit image formats.

class omni.asset_validator.core.KindChecker: All kinds must be registered and conform to the rules specified in the USD Glossary.

class omni.asset_validator.core.ExtentsChecker: Boundable prims have the extent attribute. For point based prims, the value of the extent must be correct at each time sample of the point attribute

class omni.asset_validator.core.TypeChecker: All prims must have a type defined.

Omniverse Naming Conventions

class omni.asset_validator.core.OmniInvalidCharacterChecker

Prim names in Omniverse cannot include any of the following characters:

Special symbols: ! @ # $ & * % | ~
Brackets: [ ] ( ) { } < >
Punctuation: , . `

Omniverse Layout

class omni.asset_validator.core.OmniDefaultPrimChecker: Omniverse requires a single, active, Xformable root prim, also set to the layer’s defaultPrim.

class omni.asset_validator.core.OmniOrphanedPrimChecker: Prims usually need a def or class specifier, not just over specifiers. However, such overs may be used to hold relationship targets, attribute connections, or speculative opinions.

Omniverse Material

class omni.asset_validator.core.OmniMaterialPathChecker: MDL assets require absolute paths or relative paths prefixed with ./ to resolve properly. This Rule suggests to prefix ambiguous MDL asset path(s) with a ./ to enforce that it is a relative path (i.e ./M_PlantSet_A13.mdl).

USD Schema

class omni.asset_validator.core.UsdGeomSubsetChecker: Ensures that a valid family name attribute is set for every UsdGeomSubset that has a material binding.

class omni.asset_validator.core.UsdLuxSchemaChecker: In USD 21.02, Lux attributes were prefixed with inputs: to make them connectable. This rule checker ensure that all UsdLux attributes have the appropriate prefix.

class omni.asset_validator.core.UsdMaterialBindingApi: Rule ensuring that the MaterialBindingAPI is applied on all prims that have a material binding property.

class omni.asset_validator.core.UsdDanglingMaterialBinding: Rule ensuring that the bound material exists in the scene.

USD Performance

class omni.asset_validator.core.UsdAsciiPerformanceChecker: For performance reasons, large arrays and time samples are better stored in crate files. This alerts users to any layers which contain large arrays or time sample dictionaries stored in .usda or ASCII backed .usd files.

Apple ARKit

The following rules are disabled by default.

class omni.asset_validator.core.ARKitPackageEncapsulationChecker: If the root layer is a package, then the composed stage should not contain references to files outside the package. In other words, the package should be entirely self-contained.

class omni.asset_validator.core.ARKitLayerChecker: All included layers that participate in composition should have one of the core supported file formats.

class omni.asset_validator.core.ARKitPrimTypeChecker: UsdGeomPointInstancers and custom schemas not provided by core USD are not allowed.

class omni.asset_validator.core.ARKitShaderChecker: Shader nodes must have “id” as the implementationSource, with id values that begin with “Usd*”. Also, shader inputs with connections must each have a single, valid connection source.

class omni.asset_validator.core.ARKitMaterialBindingChecker: All material binding relationships must have valid targets.

class omni.asset_validator.core.ARKitFileExtensionChecker: Only layer files and textures are allowed in a package.

class omni.asset_validator.core.ARKitRootLayerChecker: The root layer of the package must be a usdc file and must not include any external dependencies that participate in stage composition.