How to align GameObjects based on their corner not the center point

Questions & Answers
1

By default when we set position (x,y) of a GameObject, it does so based on its center point. I would like to place object A over object B based on B’s top left corner. What is happening now is if I get position of B and assign it to position of A then A’s center point align with B’s center point. What I want is A’s top left corner align with B’s top left corner. Please refer the image.

180171-object-placing.png

2

The easiest way is to create an empty object position it on left corner of your A object then make A Game Object child of this game object Now move your Parent(not child) to proper position.
Hope this helps
and maby try to look at this Set new Origin using empty GameObject
Best regards Fariborz

Edit 2 : Hey @Orbica
So yeah it makes sense to not creating parent and do all of the hard work at runtime
so maybe try this

 SpriteRenderer B = GetComponent<SpriteRenderer>();
 Vector2 upperLeft = new Vector2 (-B.bounds.extents.x, B.bounds.extents.y);

now we have upper left position of B .if we try to set the position of A to this position we should probably have this

180257-1.jpeg.png
180257-1.jpeg.png702×462 188 KB

so what we need next is to match the left upper corner of A to B … Just add half of the size of A to its X and minus the half of the size of the A to its Y .
sorry I am not at home to try this and not gonna be for some time I got some break from game dev so maybe it will answer your question feel free to try it and let me know if this worked.if this didn’t help come back to see what we can do about it :slight_smile: . best regards Fariborz

3

MidpointB-HalfSizeB(gives B top left corner) + MidpointA…

4

Here is complete code.

Call GetOverlapAlignment() function. First parameter will be be your primary object (e.g. which you are dragging or moving), second parameter will be your secondary object on which you want to place your primary object, third parameter will be which corner you want to use to match the placing.

`

public enum Corner
        {
            TopLeft,
            TopRight,
            BottomRight,
            BottomLeft
        }

    // Returns coordinates of specified corner of a game object

    public static Vector2 GetCorner(GameObject gameObject, Corner corner)
    {
        Vector2 extents = gameObject.GetComponent<Renderer>().bounds.extents;
        Vector2 cornerPosition = gameObject.transform.position; 

        if (corner == Corner.TopLeft)
        {
            cornerPosition.x -= extents.x;
            cornerPosition.y += extents.y;
        }
        else if (corner == Corner.TopRight)
        {
            cornerPosition.x += extents.x;
            cornerPosition.y += extents.y;
        }
        else if (corner == Corner.BottomRight)
        {
            cornerPosition.x += extents.x;
            cornerPosition.y -= extents.y;
        }
        else if (corner == Corner.BottomLeft)
        {
            cornerPosition.x -= extents.x;
            cornerPosition.y -= extents.y;
        }

        return cornerPosition;
    }

    // Get the position of game object with respect to game object it is overlapping beneath.
    // Game objects will be aligned based on their corners and not the center points (as it is default in Unity)

    public static Vector2 GetOverlapAlignment(GameObject primaryGameObject, GameObject secondaryGameObject, Corner cornersToMatch)
    {
        Vector2 position = new Vector2();
        Vector2 primaryBoundsExtent = primaryGameObject.GetComponent<Renderer>().bounds.extents;
        Vector2 secondaryGameObjectPosition = GetCorner(secondaryGameObject, cornersToMatch);

        if (cornersToMatch == Corner.TopLeft)
        {
            position = new Vector2(secondaryGameObjectPosition.x + primaryBoundsExtent.x, secondaryGameObjectPosition.y - primaryBoundsExtent.y);
        }
        else if (cornersToMatch == Corner.TopRight)
        {
            position = new Vector2(secondaryGameObjectPosition.x - primaryBoundsExtent.x, secondaryGameObjectPosition.y - primaryBoundsExtent.y);
        }
        else if (cornersToMatch == Corner.BottomRight)
        {
            position = new Vector2(secondaryGameObjectPosition.x - primaryBoundsExtent.x, secondaryGameObjectPosition.y + primaryBoundsExtent.y);
        }
        else if (cornersToMatch == Corner.BottomLeft)
        {
            position = new Vector2(secondaryGameObjectPosition.x + primaryBoundsExtent.x, secondaryGameObjectPosition.y + primaryBoundsExtent.y);
        }

        return position;
    }

`