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/" }
} 

There can be multiple mappings for each OS:

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