Unity用 多分一番シンプルなuGUI用仮想方向スティック実装

JoyStick.cs

/// <summary>
/// 使い方　Canvas下に空RestTransformを作りこれを貼る、下にスティック画像のImageをぶら下げてパブリックフィールドに設定する、GetAxis～から値を拾う。//
/// </summary>
/// <returns></returns>
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

public class JoyStick : Graphic, IEndDragHandler, IDragHandler, IPointerDownHandler, IPointerUpHandler
{
    public Transform padObjectTransform;
    private float padMovableRadius = 100;
    private static Vector2 axis = Vector2.zero;

    public static float GetAxisHorizontal()
    {
        return axis.x;
    }

    public static float GetAxisVertical()
    {
        return axis.y;
    }

    protected override void Awake()
    {
        base.Awake();

        Image padImage = padObjectTransform.GetComponent<Image>();
        padImage.raycastTarget = false;

        raycastTarget = true;
    }

    public void OnPointerDown(PointerEventData eventData)
    {
        OnDrag(eventData);
    }

    public void OnPointerUp(PointerEventData eventData)
    {
        OnEndDrag(eventData);
    }

    public void OnDrag(PointerEventData eventData)
    {
        //CanvasがScreen Space - Overlayの場合のみ//
        Vector2 tapPosition = transform.InverseTransformPoint(eventData.position);

        //CanvasがScreen Space - Cameraなら、たぶんこう//
        //Vector2 tapPosition = Vector2.zero;
        //RectTransformUtility.ScreenPointToLocalPointInRectangle(this.rectTransform, eventData.position, null, out tapPosition);

        //タップ位置の半径が指定半径より長かったら修正//
        if (Vector3.Distance(Vector3.zero, tapPosition) > padMovableRadius)
        {
            tapPosition = GetRadiusLimitedPosition(tapPosition, padMovableRadius);
        }

        SetPadObjectPosition(tapPosition);
    }

    //指定半径に収めた座標を返す//
    private Vector2 GetRadiusLimitedPosition(Vector2 tapPosition, float radius)
    {
        float radian = Mathf.Atan2(tapPosition.y, tapPosition.x);

        Vector2 limitedPosition = Vector2.zero;
        limitedPosition.x = radius * Mathf.Cos(radian);
        limitedPosition.y = radius * Mathf.Sin(radian);

        return limitedPosition;
    }

    //JoyStickのPad位置を設定//
    public void SetPadObjectPosition(Vector3 position)
    {
        padObjectTransform.localPosition = position;

        axis = new Vector2(
            padObjectTransform.localPosition.x / padMovableRadius,
            padObjectTransform.localPosition.y / padMovableRadius
        );
    }

    public void OnEndDrag(PointerEventData eventData)
    {
        SetPadObjectPosition(Vector3.zero);
    }
}