Classic luma matte using Render layer masks? C4D Tweet

[hqhempen]

So I'm picking up from this post that layer masks don't actually act like luma mattes:

https://render.otoy.com/forum/viewtopic.php?f=30&t=63229&p=323085&hilit=+layer+mask+#p323085

So a triangle with Octane Object Tag ID2 flying behind a sphere ID3 will render the layer mask out as if it never was concealed by the sphere at all. I can see where layer masks are useful for that, but I need it to actually render out as a matte that gets concealed. I read the Object Color property in the ObjectTag maybe has something to do with it? But I don't see how after some testing.

Is there a way to render an equivalent luma matte pass from Octane in C4D, short of coloring everything black and white?

[milanm]

Hi

Maybe this might help? (the second part of that post):
viewtopic.php?p=310305#p310305

Regards
Milan