At the root level of the project, 2D groups behave differently than when they are nested
inside 3D groups. (For more information about root-level groups, see
2D groups at the root level are locked to the camera, even if the camera is animated. 2D
groups at the top of the Layers list are rendered in the foreground, and 2D groups at the
bottom of the Layers list are rendered in the background. Adjacent root-level 3D groups
can intersect based on depth order.
In the example above, the two gray balls in the 2D “Foreground” layer are composited
on top of the rest of the scene. The 2D “Background” layer is composited beneath the
rest of the scene. “Group A” and “Group B” intersect because they are 3D groups, but
neither of them can intersect with the 2D root-level groups.