Finding a GameObject by transform.position

Questions & Answers
1

is there a way to find a gameobject by their position? I want to use it for placing blocks so that you can’t place blocks evrywhere and i want to use that to find the 4 possible gameobject(2d game) around the block you want to place.
If you know another way to fix my problem tell me.
btw you don’t have to type a full script just tell me what to do (C#)

1 Like
3

You could store each GameObject block in a 3D array, where its index corresponds to its transform’s position.

For example, you could make a Block component with the fields int x, y, z;, and attach the script to each block. Another script, BlockController, would hold a 3D array of blocks, eg Block[,,] blocks, and a static Vector3 size; for the dimensions of each block.

Then on Awake() you could set the position of the block to the index multiplied (scaled) by the block size, like so: new Vector3(x * size.x, y * size.y, z * size.z), and also add the Block to the BlockController’s blocks array via its index like so: blocks[x,y,z] = Block;

Then to get the closest block to a point, you would divide (inverse scale) the point by size and round each x,y,z component to an integer, to get its index in the blocks array.

2

There are several ways to do this.

If your positions are discrete and only one object should occupy every position then you could create a unique identifier for each position and use as key in a dictionary:

const int width = 16;
Dictionary<int, GameObject> objects = new Dictionary<int, GameObject>();

int GetKey(int x, int y) {
    return x + width * y;
}

int GetXFromKey(int key) {
    return key % width;
}

int GetYFromKey(int key) {
    return key / width;
}

public GameObject GetGameObjectAtPosition(int x, int y) {
    int key = GetKey(x, y);
    if (objects.ContainsKey(key))
        return objects[key];
    else
        return null;
}

public bool TryInstantiatePrefabAtPosition(int x, int y, GameObject prefab) {
    int key = GetKey(x, y);
    if (objects.ContainsKey(key))
        return false;
    var obj = Instantiate<GameObject>(prefab);
    obj.transform.position = new Vector2(x,y);
    InsertGameObjectAtPosition(x,y,obj);

    return true;
}
public void InsertGameObjectAtPosition(int x, int y, GameObject obj) {
    int key = GetKey(x, y);
    if (objects.ContainsKey(key))
        throw new System.Exception("Nope, position already taken...");
    else
        objects[key] = obj;
}

I haven’t tested the code, just wrote from memory from a similar solution I’ve used before so there could be some spelling errors. Let me know if it works!

If this solution does not apply then I would recommend using 2d raycast, 3d raycast or any of the other available casts available in the physics libraries

Edit: Changed the code to contain an instantiate. Call TryInstantiatePrefabAtPosition and it will return true if the object was instantiated and false otherwise.

4

@Mikael-H @SublimeGamer
hey i hoped one yo you could help me out one more time. I can only palce blocks when there is anothe block next to it, this is normal. but once i get to a specific height. i can’t place blocks anymore i know where the problem is but i have no idea how to fix it.

so how my script works is in my first script evrythime a block is created its location will be add to a list

now when i press right click to place a block it will check for this all will happen with some more bools but that’s not the problem
more explained below

    // this fix some collision bugs
    mousePosition = new Vector2(Mathf.Round(mouse.x * 2f) * 0.5f, Mathf.RoundToInt(mouse.y * 2f) * 0.5f);
                                if (!coords.Contains(mousePosition))
                                {
    // what happens here i take the rounded postion of the mouse and I make 
   //the 4 sides where the block can be placed against (north = above,...)
    //but ONCE that the Y position of one of these variables is greater than 0
    //it doesnt work anymore So the NextTo varibale doesn't turn true
                                    north = new Vector2(mousePosition.x, mousePosition.y + 0.5f);
                                    south = new Vector2(mousePosition.x, mousePosition.y - 0.5f);
                                    east = new Vector2(mousePosition.x + 0.5f, mousePosition.y);
                                    west = new Vector2(mousePosition.x - 0.5f, mousePosition.y);
if (coords.Contains(north)|| coords.Contains(east) || coords.Contains(west) || coords.Contains(south))
                                    {
//THE ABOVE IF STATEMENT DOESNT TRIGGER WHEN IT'S SUPPOSED TO TRIGGER i checked it
                                        test = true;
                                        nextTo = true;
                                    }

i have no idea why that once the Y (of one of the 4 variable) is greater than zero that it doesnt work anymore if you need some more information juts ask