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Animation blending, as a concept, simply means making a smooth transition between two or more animations on a single character or Skeletal Mesh. In Unreal Engine 4, there are various ways in which such blending can be applied. In this document, we will overview each one and how they can be applied to your characters.
Blend Spaces
One of the most common ways to blend together animations is with Blend Spaces.
Blend Spaces are special assets which can be sampled in AnimGraphs that allow for blending of animations based on the values of two inputs. Simple blending between two animations based on a single input can be performed using one of the standard Blend nodes available in Animation Blueprints . Blend Spaces provide a means of doing more complex blending between multiple animations based on multiple values (currently limited to two).
The goal of Blend Spaces is to reduce the need for creating individual, hard-coded nodes to perform blending based on specific properties or conditions. By allowing the animator or programmer to specify the inputs, the animations, and how the inputs are used to blend between animations, virtually any type of blending can be performed using the generic Blend Space.
For more information on Blend Spaces, please see the Blend Spaces documentation.
Blending with Blueprints
Animation blending can also be handled directly by way of the AnimGraph within an Animation Blueprint. The AnimGraph charts the flow of animation pose data through a series of different nodes, each node contributing in some way to the final look of the pose or motion. There are a variety of nodes specially designed to aid in blending multiple poses together in some way. These can be additive, literally combining two animations based on a weighted bias or alpha value, or can be direct overrides of the existing pose. You can also send animation directly to a specific bone in the Skeleton and all of its children. For instance, you can start with an animation in which the character is running, but then selectively apply a waving animation just to the right arm. The final result will be the character running and waving.
For an understanding of how animation blending can be handled with Blueprints, please see Animation Blueprints and Blend Nodes .