I have a pieces of a rendering I am working on. This is the gravel with all the landscape particle instances. If you look at the generated alpha channel mask, you will see that none of the small plants and bushes are excluded in the mask, like the trees are. The tress are group instances. If I render this same mask using B-Maxwell, Maxwell Render for Blender, all of the particle instances are included in the mask. I do this because the client might say make the gravel lighter or darker. This can then be done easily in the compositor or Photoshop. If the plants are not excluded in the alpha, they will get changed as well. Not good. I hope this is a bug and can be fixed.
dual E5 2660 v3's (2.6 ghz) (40 Threads) Z10PE D8 WS, 96 gigs of ram win 7 x64 GTX 970
Windows 7, Blender 2.79 official Build