Problem programming 2d grid

Questions & Answers
1

I’m trying to programming in Unity an 2d grid, where i can press the right button the mouse and the position of the mouse is used as the position to instantiate a game object. The game object will be instantiated in the cell of the grid.
So i create a matrix of Rect and I use the function of the Rect to intersect the position of the mouse and the Rect that included it.
What i have done until now seems to work, but there is a bug that i could’nt fix.
It seems that only a portion of the screen where the script work.
Can anyone help me to figure out where i’m wrong?

I pass the script:

public class GridManager : MonoBehaviour {

	public GameObject gameobject;
	public int max_row = 9;
	public int max_coll = 18;
	public int cell_width = 120;
	public int cell_height = 120;

	private GameObject[,] gameBoard;
	private Rect[,] grid;


	void Awake(){
		gameBoard = new GameObject[max_row, max_coll];
		grid = new Rect[max_row, max_coll];
		for( int y = 0; y < max_coll; y++)
		{
			for ( int x = 0; x < max_row; x++)
			{
				grid[x, y] = new Rect(x * cell_width, y * cell_height, cell_width, cell_height );

			}
		}
	}
	// Use this for initialization
	void Start () {
	
	}
	
	// Update is called once per frame
	void Update () {
	if(Input.GetMouseButtonDown(0)){
			Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
			for( int y = 0; y < max_coll; y++)
			{
				for ( int x = 0; x < max_row; x++)
				{
					if ( grid[x, y].Contains( ray.origin) )
					{
						Instantiate(gameobject, new Vector3( grid[x, y].center.x, grid[x,y].center.y, 0 ), transform.rotation);
						Debug.Log("x" + grid[x, y].center.x );
						Debug.Log("y" +  grid[x, y].center.y );
						Debug.Log("mouse x " + ray.origin.x);
						Debug.Log("mouse y " + ray.origin.y);
					}
				}
			}
		
		}
}
}
2

The problem is because your Rect[,] grid array starts at 0,0 and continues to max_row and max_coll. What you should do is offset it, so that it doesn’t start in the middle of the screen:

for( int y = 0; y < max_coll; y++)
     for ( int x = 0; x < max_row; x++)
          grid[x, y] = new Rect((x - max_row / 2) * cell_width, (y - max_coll / 2) * cell_height, cell_width, cell_height );

Here,

(x - max_row / 2) and (y - max_coll / 2)

offsets the whole grid array. It will now start in the bottom-left corner, instead of the middle of the screen, and end in the top-right corner.

Or have a look at a slightly different approach to the same problem:

using UnityEngine;

public class GridManager : MonoBehaviour {

	public Transform prefab;
	public int max_row = 9;
	public int max_coll = 18;

	void Update () {
		
		if(Input.GetMouseButtonDown(0)) {
			Vector3 pos = Camera.main.ScreenToWorldPoint(new Vector3(Input.mousePosition.x, Input.mousePosition.y, -Camera.main.transform.position.z));
			pos.x = Mathf.Clamp(Mathf.Round(pos.x), -max_row / 2, max_row / 2);
			pos.y = Mathf.Clamp(Mathf.Round(pos.y), -max_coll / 2, max_coll / 2);
			Instantiate(prefab, pos, transform.rotation);
		}
	}
}

–David