Ability to render masks per-Scatter (or per-Forest)

Users would like to have the ability to render a mask for a specific Scatter or ForestPack object as a whole. The use case is, for example, having 2 different scatters for the same types of trees in the foreground and in the background and rendering masks for for the foreground scatter and for the background scatter. Currently, this isn't possible.

Currently:

• when Scatter or ForestPack objects are added to a masking element - no mask is rendered at all (black screen renders)

• when the source objects (scattered models) are added to a masking element, the masks are rendered for those objects, but if the same model is used in multiple scatters, then the masks are no longer per-scatter. We get per-model masks rather than per-scatter.

Attaching:

• Max scenes:

  • Chaos Scatter - https://drive.google.com/file/d/1bbIKRXbDQ7j5N3dyeK4VTUWAxn9H01nE/view?usp=sharing

  • Forest Pack - https://drive.google.com/file/d/1fzY5GX2OsibUt5IrUE-WDG8d2jYZkU1L/view?usp=sharing
    
    

• user-request.jpg - what the users would like to achieve - each scatter gets its separate mask (note: this is simulated by baking the scattered objects into Max geometry, this is not an actual solution, just a showcase of what the users would like to do)
  
  

• scatter-beauty.jpg - the result of rendering the Scatter scene

• scatter-mask.jpg - the results of rendering masks for the scattered instances
  
  

• forest-beauty.jpg - the result of rendering the Forest Pack scene

• (there is no mask rendering as it would be pretty much the same as in the case of Chaos Scatter)