Animation.CrossFade

説明

time 秒に渡り他のアニメーションをフェードアウトさせながら animation という名のアニメーションをフェードインさせます。

If mode is PlayMode.StopSameLayer, animations in the same layer as animation will be faded out while animation is faded in. if mode is PlayMode.StopAll, all animations will be faded out while animation is faded in.

If the animation is not set to be looping it will be stopped and rewound after playing.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour {
    public Animation anim;
    void Start() {
        anim = GetComponent<Animation>();
    }
    void Update() {
        if (Mathf.Abs(Input.GetAxis("Vertical")) > 0.1F)
            anim.CrossFade("Run");
        else
            anim.CrossFade("Idle");
    }
}