The Arnold volume node uses the texture search path, so you don’t have to use an absolute path in the volume filename.

So if you need to set up a Maya scene so that the OpenVDB volumes work on any platform, you could put an environment variable in the Texture Search Path

Just note that support for volume filenames is still a little … rough. You can’t enter an absolute path in the aiVolume Filename box, then enter a texture search path, and expect MtoA to automatically export a relative path. That still needs to be implemented.

For now, here’s what to do:

• When you first create the volume, load the vdb file and leave the full absolute path in the aiVolume Filename box.
• Select the grids and set the other volume parameters.
• Then set the texture search path and strip off the path from the volume file name (leaving just the file name).
• Now the environment variable will control where Arnold looks for the vdb file.

The Arnold volume node also support environment variables, so you could do this:

But again, once you put the environment variable into the Filename, the path won’t be resolved inside Maya (but it will work when you render).