# Finding diagonal objects of an object in 3d space

Using Unity3d, I have a array which is having 8 GameObjects in grid and one object (which is already known) is in center like this where K is already known object. All objects are equidistant from their adjacent objects (even with the diagonal objects) which means

(distance between 4 & K) == (distance between K & 3) = (distance between 2 & K)

1 2 3
4 K 5
6 7 8

I want to remove 1,3,6,8 from array (the diagonal objects).
How can I check that at runtime?

my problem is the order of objects {1-8} is not known so I need to check each object's position with K to see if it is a diagonal object or not. so what check should I put with the GameObjects (K and others) to verify if this object is in diagonal position

Regards,
Sam

• It is really not clear what you are asking. It sounds like you have all the information you need, what is the problem? – AturSams Mar 13 '14 at 10:12
• my problem is the order of objects {1-8} is not known so I need to check each object's position with K to see if it is a diagonal object or not. so what check should I put with the GameObjects (K and others) to verify if this object is in diagonal position – Saurabh Passolia Mar 13 '14 at 10:30

One solution would be to get the normal vector between the objects and look at its x and z components. Diagonal objects will have an identical x and z length (assuming the objects are arranged on the X/Z plane, otherwise you'd have to swap components accordingly).

In code:

// MyObjects is an array or list of your corner GameObjects (1-8)
// K is your center GameObject
foreach(GameObject obj in MyObjects){
Vector3 normal = (obj.transform.position - K.transform.position).normalized;
// compare against a small float because of floating-point inaccuracies
if(Mathf.Abs(Mathf.Abs(normal.x) - Mathf.Abs(normal.z)) < 0.001){
// diagonal object detected!
}
}

If (distance between 4 & K) == (distance between K & 3) == (distance between 2 & K)


Then it's a circle, therefore there's no diagonal :) If there was a diagonal the distance between the diagonal would be sqrt(2) times bigger than the distance between the adjacent.

Pick one of the objects that is not K, and order the others by distance (ignore K). Exclude the object you picked, 4th, 5th and the final one.

Example: If you picked 1, ordering the others by distance from 1 would result:

2, 4
3, 6
5, 7
8


You'd remove 1 (the one you picked), 3 and 6 (4th, 5th), 8 (the last).