Blends two animations linearly inside of an [AnimationNodeBlendTree]. A resource to add to an [AnimationNodeBlendTree]. Blends two animations linearly based on an amount value in the [code][0.0, 1.0][/code] range. 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.