Anti-aliased depth merge, How?

When I try to compose objects by its depth with "perform depth merge" checked in in the merge tool I always get a line/edge of objects intersection aliased.

There is Zcombine node in Blender which is doing pretty much the same and it has "anti-aliased" check-box that fixes it there. Does Fusion have something similar or maybe I have to do the depth merge/Z blending some other way ?

from a pure technical point there cant be a antialiased z merge. a value in the z channel repesents a certain depth, antialiasing is a filter that would change that value and you end with a different depth.

but fusion can use the "coverage channel" from renderings to apply some antialiasing on z channel operations. but this channel is very hard to find in 3d renderers

then you can render your depth channel in 2x resolution and resize them before the z merge, this will give you some kind of filtering/antialising and can result in better looking z merges

I have downloaded Blender's source code and looked at it. There's really a function in there that anti-aliases an image that only consists of black or white pixels....

It would be a nice exercise to convert this to a Fuse (for those of you who are new to Fusion: It's a script plugin written in LUA and optionally OpenCL that is supported by the free version of Fusion 7.5)

I've pasted the algorithm over at http://www.steakunderwater.com/wesuckle ... 1077#p1077
Anybody who's interested in learning about Fusion's excellent Fuse API is invited to take a look. We're currently building a learning resource where small tools like this would be programmed in a community effort and each step and improvement to the code is fleshed out in public.

Unfortunately I am not proficient with the code so I am trying to recreate the same appearance with usual node blending. So I need to get a mask when one z value is greater then another one. I think it's possible to do using difference blending mode. At least I did so in Photoshop. Then threshold the picture to just 1 and 0 and then anti-alias it. That anti-aliasing part is where I have no ideas. I can do not pure threshold , just something very contrast or after-blur it a bit but it not seems right and produce multiples artifacts and mismatches on small details. Not the same good as Blender does

Any suggestions?