Unity get reference of GameObject under another GameObject

Question

I am trying to get reference of the object underneath my Player.

I don't know if I am aproaching this correctly. Right now, I have a player simply put in the scene, like this:

Then I am trying to get reference of it like this (does not work)

public void CheckTileUnder()
{
    Vector3 halfExtents = new Vector3(0f, -1 / 2.0f, 0f);
    Collider[] colliders = Physics.OverlapBox(transform.position, halfExtents);

foreach (Collider item in colliders)
    {
        Tile tile = item.GetComponent<Tile>();
        if (tile != null)
        {
            RaycastHit hit;

if (Physics.Raycast(tile.transform.position, Vector3.down, out hit, 1))
            {
                currentTile = tile;
            }
        }
    }
}

Another aproach that I thought of would be to put the player under the Tile like this: Then I guess I would have to change parents like suggested in one of the answers here?

How should I select the Tile under the Player?

lvictorino · Answer

It depends on how your game works. Both of your leads are correct if you just need to know what tile is under the player. Between the two, again depending on your type of game and gameplay, I'd use the one using a Raycast.

TL;DR: if you organize your grid objects in a linear way (from first to last) you could easily find the cell your player is on with a simple calculus.

However, on a grid based game, there is something less consuming than a Raycast based system or a hierarchy swap system. You could simply use Maths :) if you know the size of your grid cells, the origin of your grid, and the world position of your player... then it'd be easy to know what tile your Player is on.

Let's say that your grid is a width 5 and height 6 grid of 2 units cells. Your player is on, let's say, x: 1.2 and y:3.5. The origin (bottom left) of your grid is on 0,0.

cell_x = player_x / cell_size = 1.2 / 2 = 0.12 = 0
cell_y = player_y / cell_size = 4.5 / 2 = 2.25 = 2

In this example your player is on cell x 0 and y 2. So now... "I know the cell coordinate, but I still do have the reference of it". Now let's say you have a GameObject named grid that contains all the cell GameObject as child. The first one would be cell id 0, the second one would be id 1, ... and the last one would be id width * height - 1, in our case id 29 (5 * 6 - 1).

How to convert a x,y cell position into and id? That's pretty simple: id = y * width + x. In our example above, position x 0 and y 2 would give us id = y * width + x = 2 * 5 + 0 = 10.

To get your GameObject reference, you can get the cell child you want on your grid GameObject by: GameObject cell = grid.transform.GetChild(id).gameObject;. Et voila.

Unity get reference of GameObject under another GameObject

One Answer

Add your own answers!

Related Questions

How can I create hemisphere worlds (floating islands?) with 3d (or 2d)? Noise (Perlin/OpenSimplex)

Convert a string to a gameobject name

Jumping up quicker? (Paper Mario style jump)

A* Pathfinding Finding One of Many Goals

Wheel rotation for a raycast car in Unity?

I’m trying to instantiate game object as a child of canvas in scene but it doesn’t work

Player freezes mid air when not also moving with WASD

Smoothly switch between 2 pairs of oscillating colors

Unity “scrape away” effect

How can I let players “scrape away” one texture to reveal another?

Initial setting of camera and ppu to match playing table

LibGDX – Tilemap Wall Collision Detection Issues

Player is not looking at correct direction

How to add post process volume script in unity 2019?

Button not clickable if it’s under a Content Size Fitter + Horizontal Layout Group in Unity?

Tilemaps not showing up on Android build

Unity: Sprite stretch issue

Unity UI, how to hide on play

Alternative path not working

Unity – Understanding the SRP batcher

Ask a Question