In this lesson, you will learn how to isolate specific combat animations, like reloading or swinging a sword, to the upper body while your character continues to run or walk seamlessly.
The Logic of Layered Blending
When a character is running, their lower body is occupied by the BlendSpace locomotion state. If you simply play a "Reload" animation, it would override the entire character, causing their legs to stop moving or snap into a T-pose. To fix this, we use the Layered Blend per Bone node within our AnimGraph.
This node takes two inputs:
- Base Pose: Your existing locomotion state (the legs).
- Blend Pose: The upper body combat animation (the reload).
By specifying a "Layer Setup" inside the node, we define exactly where the blending begins. By setting the Bone Name to the spine or pelvis bone (e.g., spine_01), Unreal Engine will blend the locomotion pose for the legs and torso up to that bone, while applying the combat animation for everything from that bone upward to the hands and head.
Setting Up the Node
Inside your AnimGraph, create a Layered Blend per Bone node. In the Details panel, expand the Layer Setup array and add an element. Define the Bone Name to match your skeleton’s hierarchy.
// Logic flow inside the AnimGraph:
// Locomotion (BlendSpace) -> Base Pose
// Combat Action (Sequence) -> Blend Pose
// Layered Blend per Bone (Bone Name: "spine_01") -> Output Pose
To ensure the transition isn't jarring, ensure your Blend In and Blend Out times are configured. Using a "Mesh Space" rotation blend is often preferred for upper-body actions to ensure the arms maintain correct orientation regardless of the character’s movement direction. This technique preserves the integrity of your Locomotion State Machine while allowing for fluid, independent combat actions.
Key Takeaway: By targeting a specific bone in the skeletal hierarchy, you create a surgical split that allows combat animations to run on the upper body without interrupting the locomotion logic driving the character's legs.