fps-citybuild-unity/Assets/Scripts/Building/BuildingPlacement.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class BuildingPlacement : MonoBehaviour
{
    [SerializeField] private GameObject terrain;
    [SerializeField] private GameObject prefab;

    Ray ray;

    void Update()
    {
        // Build Button Handler
        if (Input.GetButtonDown("Build"))
        { // Wenn man den Button 'B'
            ray = Camera.main.ScreenPointToRay(Input.mousePosition);
            RaycastHit hitData;
            if (terrain.GetComponent<Collider>().Raycast(ray, out hitData, Mathf.Infinity))
            {
                Instantiate(prefab, hitData.point, Quaternion.identity);

            }
        }
    }
}