Sorry, I was generalizing. Typically, you have a material on the PP, and writing to that is much easier with a MPC.
But in the case of a bare PP volume, then you do need to have a reference and use the settings node 
Sorry, I was generalizing. Typically, you have a material on the PP, and writing to that is much easier with a MPC.
But in the case of a bare PP volume, then you do need to have a reference and use the settings node