如何使用鼠标位置在Unity中的2D网格上放置图块？

Question

I am trying to make a level editor to where the user can click where they want a tile to be placed. Here is the code:

using UnityEngine;
using System.Collections;

public class TilePlacement : MonoBehaviour {

    // Use this for initialization
    void Start () {

    }

    // Update is called once per frame
    void Update () {
        if (Input.GetMouseButtonDown (0)) {
            var clickPos = new Vector3(Input.mousePosition.x, Input.mousePosition.y, 0f);
            clickPos = Camera.main.ScreenToWorldPoint (clickPos);

            clickPos.z = 0f;
            clickPos.x = Mathf.FloorToInt (clickPos.x);
            clickPos.y = Mathf.FloorToInt (clickPos.y);
            clickPos.x /= 3.2f;
            clickPos.y /= 3.2f;
            clickPos.x = Mathf.Round (clickPos.x);
            clickPos.y = Mathf.Round (clickPos.y);
            clickPos.x *= 3.2f;
            clickPos.y *= 3.2f;

            var go = new GameObject ();
            go.AddComponent<SpriteRenderer> ();
            go.GetComponent<SpriteRenderer> ().sprite = Sprite.Create(new Texture2D(32, 32), new Rect(0, 0, 32, 32), new Vector2(0, 0));
            go.transform.localScale = new Vector3 (10f, 10f, 0f);
            go.transform.position = clickPos;
        }
    }
}

This code works for placing tiles but the user has to click in the bottom left corner of a tile and the formula for changing clickPos seems too complicated and I think there is a better way to do it. Please help me fix these two problems

Answer 1

Are you working in 2D with an orthographic camera? In 3D I would do it like this, which also works for 2D planes.

Plane _groundPlane;

void Start()
{
    _groundPlane = new Plane(Vector3.up, Vector3.zero);
}

void Update()
{
    if (Input.GetMouseButtonDown(0) == false)
        return;


    int x = 0;
    int z = 0;
    Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
    float distance;
    if (_groundPlane.Raycast(ray, out distance))
    {
        Vector3 worldPosition = ray.GetPoint(distance);
        x = Mathf.RoundToInt(worldPosition.x);
        z = Mathf.RoundToInt(worldPosition.z);

        Debug.DrawLine(Camera.main.transform.position, worldPosition);
        Debug.LogFormat("Clicked positions: {0} | {1}", x, z);
    }
}

I create a Plane that lies flat with the default grid. Then I do a raycast against it to find the hit point from the mouse screen position in world space. I also made each cell one unit in size, so that I can round to int to get the index position, which also works as the world transform position.

If you want to save the raycast and don't need a 3D camera perspective, you can simply get the mouse world position like you are already doing. If you make each tile one unit big, everything will just work when rounded to int.