Cannot open file on render farm: Maya texture reference resolution

Answer to the Core Questions

1. Making dirmap rules persistent without editing each job script

• Place the dirmap commands in userSetup.mel located at ~/maya/version/scripts/userSetup.mel (or a shared module in MAYA_MODULE_PATH). Maya loads this file automatically in batch mode, so every render node inherits the mapping.
• Example entry:

  dirmap -set "Z:/Textures" "/mnt/textures";
  dirmap -enforce true;

• To confirm the mapping is active, run on a node:

  maya -batch -command "dirmap -q;"

2. Synchronizing Arnold’s ARNOLD_TEXTURE_PATH with Maya’s search path

• Export the same texture root into the farm’s environment. For example, add to /etc/environment or the render manager’s job wrapper:

  export ARNOLD_TEXTURE_PATH=/mnt/textures

• Arnold reads this variable at plugin load time; ensure it is set before Maya starts (e.g., in a shell wrapper that launches maya).
• If multiple roots are needed, separate them with the OS path separator (: on Linux). Example:

  export ARNOLD_TEXTURE_PATH=/mnt/textures:/mnt/extra_textures

• Verify inside a batch render log that the variable is present: search for ARNOLD_TEXTURE_PATH or use getenv in a MEL command.

3. Studio policy recommendation

• For new projects, enable Use Relative Paths for Textures (File > Project Window) and run File > Optimize Scene Size > Convert Absolute Texture Paths to Relative before submission. This writes relative paths into the .ma/.mb files, eliminating the need for dirmap or environment overrides.
• For legacy scenes that must retain absolute paths, deploy a single, version‑controlled JSON map (e.g., path_map.json) and load it in userSetup.py or a Maya module. The script calls dirmap for each entry, keeping all mapping logic in one place.
• Never rely on per‑job shell edits; use the shared userSetup or module approach for maintainability.

Likely Explanation vs. Confirmed Facts

Likely Explanation: The scene contains Windows absolute paths that cannot be resolved on Linux nodes because the drive letter (Z:) does not exist, and the farm lacks the ARNOLD_TEXTURE_PATH variable. The dirmap rules defined in the UI are session‑only and thus not present during batch render.

Confirmed Facts (from research):

• Adding dirmap rules to userSetup.mel persists across batch renders.
• Arnold reads ARNOLD_TEXTURE_PATH only once at plugin load, so the variable must be exported before Maya starts.
• Relative paths in the scene eliminate the need for mapping entirely.

Missing Diagnostic Detail Needed

To fine‑tune the recommendation, please confirm the current value of ARNOLD_TEXTURE_PATH on the farm nodes. If it is already set to the correct texture root, the mapping step can be omitted.

Practical Verification Steps

1. On a farm node, run:

   maya -batch -command "dirmap -q;"

2. Check the log for Cannot open file messages after opening a test scene.
3. Render a single frame with mayapy and inspect the Arnold log for texture lookup paths.
4. Compare the rendered EXR metadata (e.g., exiftool) between workstation and farm to ensure identical texture resolution.

Conclusion

Persisting dirmap in userSetup.mel and aligning ARNOLD_TEXTURE_PATH across the farm are the most robust solutions for legacy absolute paths. For new work, moving to relative paths is the simplest long‑term strategy. A single, controlled mapping file or module keeps the workflow maintainable without per‑job edits.