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MDL Path Resolution Changes#

Summary of the changes for resolving MDL paths:

  • MDL built-in paths (i.e OmniPBR.mdl, OmniPBR_ClearCoat.mdl, OmniSurface, nvidia/aux_definitions.mdl, nvidia/core_definitions.mdl, OmniUE4Base.mdl, etc.) will no longer be anchored to their referencing layer URL (e.g. https://server/some/other/stage.usd). These MDL built-in paths will still resolve correctly if they live next to the referencing layer URL but that is completely handled by the client-library and not USD

  • MDL paths not prefixed with “./” or “../” can still be anchored relative to the referencing layer if they exist and the referencing layer is a URL or file path on disk

  • MDL built-in paths are no longer considered search paths

  • MDL built-in paths are no longer considered relative paths unless prefixed with “./” or “../”

  • This behavior works through SdfAssetPath type Attributes without modifying Sdf

  • This behavior can be enabled / disabled by setting the environment variable OMNI_USD_RESOLVER_MDL_BUILTIN_BYPASS or in <APPLICATION>/kit/extscore/omni.usd.config/omni/usd_config/extension.py

  • At the moment, this resolve behavior is disabled by default by can be easily switched