The ability to drop some geometry into a render scene and use it as a mask for rendering selected on ID
So you would like to have both? Area rendering and selected only? Assuming you have everything animated (moving objects + moving cam) you could:
- Xref the object of interest from one of your xref scenes additionally into your main scene
- Set it's renderable property to off
- Create a sphere with a radius covering the area you want to render
- Set the spheres renderable property to off (and "See-through" to on, makes it easier)
- Align and link the sphere to the xref object
- Use "Area to Render" -> "Region" with "Auto Region Selected" ticked in render setup
- Select Sphere
- Render sequence
Additionally you now could add Corona Object GBuffer ID render selected feature to mask the object(s) (by setting the object ID in the xref scene).
Problem with all "selected" methods is: you cannot send the scene to a farm. In this case I would try the workaround maru mentioned but using the Include/Exclude list feature instead.
Good Luck