GridController.cs

using UnityEngine;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

public class GridController : MonoBehaviour {

    float worldX = 1F;
    float worldY = 1F;
    float worldZ = 1F;
    bool IsGenerated = false;
    List<GameObject> gridCubesList = new List<GameObject>();
    float snap = 0.2F;
    public GameObject prefab;
    List<GameObject> freeCubesList = new List<GameObject>();
    GameObject[] freeCubes = null;
    List<GameObject> GroundObjectCubesList = new List<GameObject>();
    GameObject[] GroundObjectCubes;
    List<GameObject> possibleCubesList = new List<GameObject>();
    GameObject[] possibleCubes = null;
    List<Vector3> localPositionsList = new List<Vector3>();
    Vector3[] localPositions = null;
    List<Vector3> globalPositionsList = new List<Vector3>();
    Vector3[] globalPositions;
    List<float> distanceList = new List<float>();
    float[] distances = null;
    int minIndex; // Shortest distance

    // Use this for initialization
    void Start () {

    }

    // Update is called once per frame
    void Update () {

    }

    // Generate grid given point as its 0, 0, 0 (rounded to 0.2)
    public void Generate (Vector3 hit){
        this.transform.position = hit;
        Vector3 position = this.transform.position;
        position.x = Mathf.Round(position.x / snap) * snap;
        position.y = Mathf.Round(position.y / snap) * snap;
        position.z = Mathf.Round(position.z / snap) * snap;
        this.transform.position = position;
        Vector3 gridStart = transform.position - new Vector3(worldX, worldY, worldZ);
        for(float x =0F; x<worldX; x += snap) {
            for(float y =0F; y<worldY; y += snap) {
                for(float z =0F; z<worldZ; z += snap) {
                    GameObject gridCube = Instantiate(prefab) as GameObject;
                    Vector3 startPosition = transform.position - new Vector3(worldX, worldY, worldZ);
                    gridCube.transform.position = new Vector3(gridStart.x + x, gridStart.y + y, gridStart.z + z);
                    gridCubesList.Add(gridCube);
                }
            }
        }
        IsGenerated = true;
    }

    public void Clear (){
        foreach(GameObject clear in gridCubesList){
            Destroy(clear);
        }
        freeCubesList = null;
        freeCubes = null;
        GroundObjectCubesList = null;
        GroundObjectCubes = null;
        possibleCubesList = null;
        possibleCubes = null;
        localPositionsList = null;
        localPositions = null;
        globalPositionsList = null;
        globalPositions = null;
        distanceList = null;
        distances = null;
    }
    // Get closest free point in grid
    public Vector3 snapPoint (GameObject GroundObject){
        GroundObject.transform.position = this.transform.position;
        foreach (GameObject gridCube in gridCubesList){
            if(gridCube != null){
                gridTrigger trigger = gridCube.GetComponent<gridTrigger>();
                if(trigger.isTriggered(GroundObject)){
                    localPositionsList.Add(this.transform.position - gridCube.transform.position);
                    localPositions = localPositionsList.ToArray();
                    GroundObjectCubesList.Add(gridCube);
                    GroundObjectCubes = GroundObjectCubesList.ToArray();
                }
                if(trigger.isTriggered(null) != true){
                    freeCubesList.Add(gridCube);
                //  freeCubes = freeCubesList.ToArray();
                }
            }
        }

    //  foreach (GameObject current in freeCubes){
        /*  foreach(Vector3 localPosition in localPositions){
                foreach (GameObject freeCube in freeCubes){
                    Vector3 globalPosition = freeCube.transform.position + localPosition;
                    globalPositionsList.Add (globalPosition);
                    globalPositions = globalPositionsList.ToArray();
                    if(globalPosition == freeCube.transform.position){
                        possibleCubesList.Add(freeCube);
                        possibleCubes = possibleCubesList.ToArray();
                    }
                }
            }*/
    //  }
    /*  foreach (GameObject possibleCube in possibleCubes){
            distanceList.Add(Vector3.Distance(possibleCube.transform.position, transform.position));
            distances = distanceList.ToArray();
        } */
        //minIndex = Array.IndexOf(distances, distances.Min());
        //return possibleCubes[minIndex].transform.position;
        return Vector3.zero;
    }
}