What does the 'Blend Depth' parameter in 'Layered Blend Per Bone' do?

Hi, I’ve been studying how to use additive animations & came upon this node called Layered Bone Per Depth. Within it’s properties there is a parameter ‘Blend Depth’. The documentation for additive animations only instructs to set it to ‘1’
& not what it actually does. Could someone please explain how this parameter works?

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I’m looking forward to get an answer to this, since I’ve found no documentation and nobody seems to state it clearly in any of the posts I’ve seen.

I am going to raise this from the dead because there is no real documentation. this is also one of the most un-intuitive ways of doing bone masking I have ever encountered. I much prefer just a simple list of bones. this system is powerful but really hard to understand at first.

This is using 4.17.2

ok so I have a simple character, here is a snippet of the hierarchy:

  spine
    spine1
      spine2
        LeftShoulder
          (left arm bones)
        RightShoulder
          (right arm bones)
        Neck
          Head

Here is his base animation and the blend animation i want to mask. I have rotated his spine over and rotated his shoulders up, and rotated his head and neck back. these are both fed into the layered blend per bone node.

ok so lets make our goal to JUST mask the spine.
here I have added a branch filter to my layered blend per bone. The results are “spine” and all of its children are using the funky anim:

now lets add another entry into our Branch Filters. enter Spine1 and set its blend depth to -1

Now we are getting somewhere! with this setup we are only applying the blend animation to the first spine link (Spine). the -1 acts like a “block”.

lets try another, here we change our “block” form spine1 to LeftShoulder. Now all children of the first spine bone are using the blended animation except our left shoulder and entire left arm (all the children of the left shoulder)

lets finish this up. remember that our plan was to only apply the blend animation the spine bones. here is how we would set this up:

Now we are only applying the blended animation to our spine. Is this the “correct” way to use this node? I have no idea. this is just how i have figured out how to use it, if someone sees this thread and has a better answer i would be extremely happy to be corrected!

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I’d like to add to the already wonderful answer that asmischney gave.

Consider the following bone chain:
Spine1 → Spine2 → Spine3 → Neck

Here’s an explanation to the Blend Depth if you set it to a number greater than 0.

BoneName = Spine1

BoneDepth = 3

The blend strength of Spine1 will be 33%, Spine2 will be 66%, Spine3 and EVERY bone that is a child of Spine3 will get the full 100% blend strength.

The Bonedepth value basically allows you to get a smoooth blend… Compared to just setting it to ‘1’ where it will have all of the child bones have 100% blend strength.

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Very important!

Thanks gooseman1977, i didnt know that lol. I wish epic had a bit more documentation!

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what? wow thank you