# BlendTreeAnimation A collection of animations on the same property that the framework blends to a single animation. ``` struct BlendTreeAnimation where Value : AnimatableData ``` ## Overview 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 [`root`](/documentation/RealityKit/BlendTreeAnimation/root), which consists of one or more blend-tree nodes ([`BlendTreeNode`](/documentation/RealityKit/BlendTreeNode)). Each node may be one of the following conforming types: - [`BlendTreeBlendNode`](/documentation/RealityKit/BlendTreeBlendNode), which branches the tree for every element in [`sources`](/documentation/RealityKit/BlendTreeBlendNode/sources) - [`BlendTreeSourceNode`](/documentation/RealityKit/BlendTreeSourceNode), which defines one of the animations to blend via its [`source`](/documentation/RealityKit/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( name: "anim1", from: JointTransforms([Transform(scale: SIMD3(1, 2, 3), rotation: simd_quatf(ix: 5, iy: 6, iz: 7, r: 8), translation: SIMD3(10, 20, 30))]), to: JointTransforms([Transform(scale: SIMD3(11, 21, 31), rotation: simd_quatf(ix: 50, iy: 60, iz: 70, r: 80), translation: SIMD3(100, 200, 300))]), duration: 1.0) let anim2 = FromToByAnimation( name: "anim2", from: JointTransforms([Transform(scale: SIMD3(10, 20, 30), rotation: simd_quatf(ix: 4, iy: 5, iz: 5, r: 7), translation: SIMD3(100, 200, 300))]), to: JointTransforms([Transform(scale: SIMD3(110, 210, 310), rotation: simd_quatf(ix: 500, iy: 60, iz: 70, r: 80), translation: SIMD3(1000, 2000, 3000))]), duration: 10.0) let blendTree = BlendTreeAnimation( 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 ``doc://com.apple.RealityKit/documentation/RealityKit/BlendWeight``, such as with the > ``doc://com.apple.RealityKit/documentation/RealityKit/BlendWeight/bindTarget(_:defaultWeight:)`` or > ``doc://com.apple.RealityKit/documentation/RealityKit/BlendWeight/parameter(_:defaultWeight:)`` enumeration cases. ## Topics ### Creating an animation [`init(_:name:isAdditive:bindTarget:blendLayer:repeatMode:fillMode:trimStart:trimEnd:trimDuration:offset:delay:speed:)`](/documentation/RealityKit/BlendTreeAnimation/init(_:name:isAdditive:bindTarget:blendLayer:repeatMode:fillMode:trimStart:trimEnd:trimDuration:offset:delay:speed:)) Creates a unique animation from a combination of other animations in the form of a tree. ### Configuring the animation [`root`](/documentation/RealityKit/BlendTreeAnimation/root) The first node in a tree of animations. [`name`](/documentation/RealityKit/BlendTreeAnimation/name) A textual name for the animation. [`bindTarget`](/documentation/RealityKit/BlendTreeAnimation/bindTarget) A textual name that identifies the particular property that animates. [`blendLayer`](/documentation/RealityKit/BlendTreeAnimation/blendLayer) The order in which the framework composites the animation. [`isAdditive`](/documentation/RealityKit/BlendTreeAnimation/isAdditive) A Boolean value that indicates whether the animation builds on the current state of the target entity or resets the state before running. ### Timing the animation [`speed`](/documentation/RealityKit/BlendTreeAnimation/speed) A factor that increases or decreases the animation’s rate of playback. [`delay`](/documentation/RealityKit/BlendTreeAnimation/delay) An amount of time that lapses before the animation plays. [`duration`](/documentation/RealityKit/BlendTreeAnimation/duration) The total playback time of the animation. [`offset`](/documentation/RealityKit/BlendTreeAnimation/offset) The time, in seconds, at which the animation begins within the duration. [`trimDuration`](/documentation/RealityKit/BlendTreeAnimation/trimDuration) An optional duration that overrides the calculated duration. [`trimStart`](/documentation/RealityKit/BlendTreeAnimation/trimStart) The optional time, in seconds, at which the source animation plays. [`trimEnd`](/documentation/RealityKit/BlendTreeAnimation/trimEnd) The optional time, in seconds, at which the source animation stops. ### Repeating animation playback [`repeatMode`](/documentation/RealityKit/BlendTreeAnimation/repeatMode) An option that determines how the animation repeats. [`fillMode`](/documentation/RealityKit/BlendTreeAnimation/fillMode) An option that determines which data displays outside of the normal duration. --- Copyright © 2026 Apple Inc. 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