WorldPositionButton.cs

using UnityEngine;
using UnityEngine.UI;

public class WorldPositionButton : MonoBehaviour
{
	[SerializeField]
	private Transform targetTransform;

	private RectTransform rectTransform;
	private Image image;

	private void Awake()
	{
		rectTransform = GetComponent<RectTransform>();
		image = GetComponent<Image>();
	}

	private void Update()
	{
		var screenPoint = Camera.main.WorldToScreenPoint(targetTransform.position);
		rectTransform.position = screenPoint;

		var viewportPoint = Camera.main.WorldToViewportPoint(targetTransform.position);
		var distanceFromCenter = Vector2.Distance(viewportPoint, Vector2.one * 0.5f);

		var show = distanceFromCenter < 0.3f;

		image.enabled = show;
	}
}