Blends two animations additively inside of an [AnimationNodeBlendTree]. A resource to add to an [AnimationNodeBlendTree]. Blends two animations additively based on an amount value in the [code][0.0, 1.0][/code] range. https://docs.godotengine.org/en/3.3/tutorials/animation/animation_tree.html If [code]true[/code], sets the [code]optimization[/code] to [code]false[/code] when calling [method AnimationNode.blend_input], forcing the blended animations to update every frame.