Blender Git Commit Log

New render feature:

If you define multiple RenderLayers with different view-layers, these
view-layers are rendered entirely, not looking at the faces that are
invisible. This allows layered composite, but only when geometry does
not intersect or overlap partially.

This new Renderlayer option "All Z values" will fill in the Z of not
visible faces (in the Scene view-layers) as well, which then allows
masking out as if these faces were set to Material option "Env".

Here's an example composite to show the effect:

Two cubes, in view-layers 1 and 2, and rendered in 2 RenderLayers:
http://www.blender.org/bf/all_z0.jpg

Same scene, but with both RenderLayers set to "All Z values":
http://www.blender.org/bf/all_z.jpg