PxrAOVLight is a handy utility light that allows a lighting artist to output a shot-specific AOV mask without needing to request one from the shading artists.
Light Linking with PxrAovLight
Use Light Linking to include/exclude pieces of geometry in the AOV. In this example, the PxrAovLight is "off" globally and "on" the tree in the scene. This linking set up creates creates a mask of the tree.
Light Filters and PxrAovLight
Because PxrAovLight is a "light", we can add a light filters to modify the output AOV. In this example, the PxrIntMultLightFilter is attached to PxrAovLight. The Light Filter is only linked to the tree trunk, resulting in a gray value for the tree trunk mask.