MtoA uses these environment variables:

• ARNOLD_PLUGIN_PATH is for shaders.
  MtoA and kick use this environment variable. Arnold doesn’t (when you write Arnold code that loads an ASS file, Arnold doesn’t getenv ARNOLD_PLUGIN_PATH)

• MTOA_TEMPLATES_PATH is for the Attribute Editor (AE) templates of Arnold shaders. For example, if you use the alShaders:

  set MTOA_TEMPLATES_PATH  C:\solidangle\alShaders\alShaders-win-1.0.0rc18-ai4.2.12.2\ae

• MTOA_EXTENSIONS_PATH is for MtoA extensions like Yeti. By default, MTOA_EXTENSIONS_PATH points to the extensions folder in the MtoA installation.

• MAYA_CUSTOM_TEMPLATE_PATH is for Node Editor templates for Arnold shaders. For example, if you use the alShaders:

  set MAYA_CUSTOM_TEMPLATE_PATH C:\solidangle\alShaders\alShaders-win-1.0.0rc18-ai4.2.12.2\aexml

• My personal favorite, MTOA_STARTUP_LOG_VERBOSITY, sets the MtoA log verbosity during startup: 1 for Errors and Warnings, 2 for Errors, Warnings, and Info, and 3 for all. This can be handy for troubleshooting MtoA loading problems.

• MTOA_LOG_PATH is the default location for Arnold log files.

These are not MtoA environment variables: