BlendTreeAnimation

struct · iOS 15.0+ · SDK 27.1

struct BlendTreeAnimation<Value> where Value : AnimatableData

A collection of animations on the same property that the framework blends to a single animation. This structure provides a way to form a single animation by mixing several other animations together. You define a source node for each animation, and a weight, which determines how much each individual animation takes effect in the resulting animation. To create the blended animation, you define a _blend tree_ that sprouts from ``BlendTreeAnimation/root``, which consists of one or more blend-tree nodes (``BlendTreeNode``). Each node may be one of the following conforming types: - ``BlendTreeBlendNode``, which branches the tree for every element in ``BlendTreeBlendNode/sources`` - ``BlendTreeSourceNode``, which defines one of the animations to blend via its ``BlendTreeSourceNode/source`` property Because source nodes reference no other nodes, they represent leaf nodes in the tree. ### Blending two skeletal movements to a single movement The following animation plays a sampling of the animations named `anim1` and `anim2`. To fine-tune the interplay between the two animations, the code sets a blend weight for each animation. The weight of `0.25` for `anim1` determines that the first animation's behavior is 25% prominent in the final result. The `anim2` weight is `0.75`, as the cumulative blend weight across all animations in the tree needs to equal `1`. This determines that the second animation influences 75% of the visual behavior of the blended animation. ```swift let anim1 = FromToByAnimation<JointTransforms>( name: "anim1", from: JointTransforms([Transform(scale: SIMD3<Float>(1, 2, 3), rotation: simd_quatf(ix: 5, iy: 6, iz: 7, r: 8), translation: SIMD3<Float>(10, 20, 30))]), to: JointTransforms([Transform(scale: SIMD3<Float>(11, 21, 31), rotation: simd_quatf(ix: 50, iy: 60, iz: 70, r: 80), translation: SIMD3<Float>(100, 200, 300))]), duration: 1.0) let anim2 = FromToByAnimation<JointTransforms>( name: "anim2", from: JointTransforms([Transform(scale: SIMD3<Float>(10, 20, 30), rotation: simd_quatf(ix: 4, iy: 5, iz: 5, r: 7), translation: SIMD3<Float>(100, 200, 300))]), to: JointTransforms([Transform(scale: SIMD3<Float>(110, 210, 310), rotation: simd_quatf(ix: 500, iy: 60, iz: 70, r: 80), translation: SIMD3<Float>(1000, 2000, 3000))]), duration: 10.0) let blendTree = BlendTreeAnimation<JointTransforms>( blend( BlendTreeSourceNode( source: anim1, name: "anim1", weight: .value(0.25)), BlendTreeSourceNode( source: anim2, name: "anim2", weight: .value(0.75)), name: "blend"), name: "blendTree", bindTarget: .parameter("bar") ) ``` - Tip: To modify the weights for each frame, create a source node with a dynamic ``BlendWeight``, such as with the ``BlendWeight/bindTarget(_:defaultWeight:)`` or ``BlendWeight/parameter(_:defaultWeight:)`` enumeration cases.

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