Just to r-cap everything for those running into similar issues:
1 - On the animation files that you want to make additive: Make sure you have “Additive settings” set to local (you can use mesh but I don’t recommend it, it is unstable and prone to breaking your rig).
2 - In AnimBP make sure you have “Apply additive” node instead of “Blend layers”.
3 - Plug the NON Additive base layer to the “Base” on the node and your additive animation layer to the “Additive” on the node, use alpha to blend between them.
4 - Now the tricky bit that created all the confusion:
- Most of the time you will need to have a state machine for your additive animations as well, this is to control and play the additive properly, otherwise you have a constant looping additive animation and an alpha that would switch to it randomly which is not desired or correct. For instance in this state machine you may have an “idle” additive frame pose mixed with your “getting hit” additive animation blended together when you fire in a BP.
The thing to watch out for here is to make sure that** ALL **animations inside state machines hooked to the “Additive” slot of the “Apply additive” node must be set to additive themselves. But you also have to be careful because lets say you have one “Idle” animation, and you can’t use one idle set to additive in a non additive layer (such as if you have the same idle animation being used already on the base layer) this now destroys your base layer animations. So you need to duplicate this “Idle” set one to additive and keep the original to be used on the base while you put the new one in additive state machine.
To Epic:
1 - I don’t understand why you need to SET a layer to be considered “Additive” in the first place when in other software as soon as a layer is inside a state machine or an additive node, it automatically considers them additive!
2 - What is up with mesh based and local space? It is confusing and all the time mesh based never worked, it best to stick with one because Additive is just that one type additive. I don’t understand why you need extra options for it. Just pick the reference frame if you need it otherwise just keep it as is.
3 - If the above is solved then the second issue is also automatically solved since the blend nodes will just create additive animation regardless the type of animation plugged into it.
4 - Better docs and explanation on this please, not a single tutorial or live stream mentions these points from the many days of searching I did.
5 - Keep UI consistent, I hate to bring Unity up all the time but they are really doing a good job keeping things in one place instead of jumping back and forth. Proof is that most of us figured out the animation tools and took us a whole thread here + days of troubleshoot to do the same thing.