Arnold 126.96.36.199 added support for per-light AOVs for volumetrics.
Here’s how to set up per-light AOVs in MtoA 188.8.131.52:
- In the light Attribute Editor, enter a name for the light group.
- Create a custom AOV for the light group. Give the AOV a name that starts with “volume_”. For example, if the light group name is “red”, then the AOV name is “volume_red”.