Python Resolver


Python based implemention of the file resolver:

  • A simple mapping pair look up in a provided mapping pair Usd file. The mapping data has to be stored in the Usd layer metadata in an key called mappingPairs as an array with the syntax ["sourcePathA.usd", "targetPathA.usd", "sourcePathB.usd", "targetPathB.usd"]. (This is quite similar to Rodeo's asset resolver that can be found here using the AR 1.0 specification.)
  • The search path environment variable by default is AR_SEARCH_PATHS. It can be customized in the CMakeLists.txt file.
  • You can use the AR_ENV_SEARCH_REGEX_EXPRESSION/AR_ENV_SEARCH_REGEX_FORMAT environment variables to preformat any asset paths before they looked up in the mappingPairs. The regex match found by the AR_ENV_SEARCH_REGEX_EXPRESSION environment variable will be replaced by the content of the AR_ENV_SEARCH_REGEX_FORMAT environment variable. The environment variable names can be customized in the CMakeLists.txt file.
  • The resolver contexts are cached globally, so that DCCs, that try to spawn a new context based on the same mapping file using the Resolver.CreateDefaultContextForAsset, will re-use the same cached resolver context. The resolver context cache key is currently the mapping file path. This may be subject to change, as a hash might be a good alternative, as it could also cover non file based edits via the exposed Python resolver API.
  • Resolver.CreateContextFromString/Resolver.CreateContextFromStrings is not implemented due to many DCCs not making use of it yet. As we expose the ability to edit the context at runtime, this is also often not necessary. If needed please create a request by submitting an issue here: Create New Issue
  • This resolver has feature parity to the file resolver, but the implementation is slightly different. The goal of this resolver is to enable easier RnD by running all resolver and resolver context related methods in Python. It can be used to quickly inspect resolve calls and to setup prototypes of resolvers that can then later be re-written in C++ as it is easier to code database related pipelines in Python.
  • Running in Python does not allow proper multithreading due to Python's Global Interpreter Lock, so this resolver should not be used in (large scale) productions.

Resolver Environment Configuration

  • AR_SEARCH_PATHS: The search path for non absolute asset paths.
  • AR_SEARCH_REGEX_EXPRESSION: The regex to preformat asset paths before mapping them via the mapping pairs.
  • AR_SEARCH_REGEX_FORMAT: The string to replace with what was found by the regex expression.

The resolver uses these env vars to resolve non absolute asset paths relative to the directories specified by AR_SEARCH_PATHS. For example the following substitutes any occurrence of v<3digits> with v000 and then looks up that asset path in the mapping pairs.

export AR_SEARCH_PATHS="/workspace/shots:/workspace/assets"

Debug Codes

Adding following tokens to the TF_DEBUG env variable will log resolver information about resolution/the context respectively.


For example to enable it on Linux run the following before executing your program: