How Arnold handles paths

When you render a frame, here's what Arnold does for file paths:

  1. Replace backslashes

    When Arnold loads an ass file, Arnold replaces all backslashes ( \ ) with forward slashes ( / )

  2. Expand environment variables

    When Arnold uses a parameter, Arnold expands all environment variable references, which look like this: [MY_TEXTURE_PATH]

  3. Map paths

    After Arnold expands environment variables, Arnold applies the path-mapping rules specified by the Arnold pathmap file.


Arnold expands environment variable expansion and maps paths for:

  • search paths in the options node 
  • filename parameters for these nodes:
    • alembic
    • color_manager
    • all driver nodes such as driver_deepexr, driver_exr, driver_jpg, driver_png, and driver_tiff
    • image
    • include_graph
    • materialx
    • photometric_light
    • procedural
    • volume
    • volume_implicit

Setting up path mapping

You can automatically remap paths at render time using a pathmap file. 

To use a pathmap

  • Set the ARNOLD_PATHMAP environment variable to point a pathmap file

 

The pathmap file is a json file. For example:

{
         "windows": { "S:/": "\\server\projects\" },
         "mac": { "S:/": "/Volumes/projects/"},
         "linux": {"S:/": "/mnt/projects/"}
}

 

Path mapping uses regular expressions. The general format of an entry is this:

{
         "windows": { "regular expression": "replacement string" },
}

For example, this pathmap replaces all drive mappings like E:/ and S:/ with //SERVER/

{
         "windows": { "[A-Z]:/": "//SERVER/" },
}

Arnold converts backslashes ( \ ) to forward slashes ( / ) when it loads the ASS file.

Path mapping happens after that, so pathmaps never have to deal with backslashes.

 

There can be multiple mappings for each OS:

{
         "windows": { "[A-Z]:": "//SERVER", "sourceimages/": "textures/"},
}

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