Clustering 3D Markers

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

public class Group3DMarkers:MonoBehaviour
{
    public GameObject prefab;
    public GameObject groupPrefab;

    public int countMarkers = 100;
    public float distance = 30f / OnlineMapsUtils.tileSize; // pixels / 256

    private List<OnlineMapsMarker3D> markers;

    private void Start()
    {
        markers = new List<OnlineMapsMarker3D>();

        for (int i = 0; i < countMarkers; i++)
        {
            OnlineMapsMarker3D marker = OnlineMapsControlBase3D.instance.AddMarker3D(new Vector2(Random.Range(-180f, 180f), Random.Range(-80, 80)), prefab);
            marker.label = "Marker " + i;
            markers.Add(marker);
        }

        GroupMarkers();
    }

    private void GroupMarkers()
    {
        List<MarkerGroup> groups = new List<MarkerGroup>();
        float sqrDist = distance * distance;
        OnlineMaps map = OnlineMaps.instance;

        for (int zoom = OnlineMaps.MAXZOOM; zoom >= 3; zoom--)
        {
            List<OnlineMapsMarker3D> ms = markers.ToList();

            for (int j = 0; j < ms.Count - 1; j++)
            {
                OnlineMapsMarker3D marker = ms[j];
                MarkerGroup group = null;
                double px, py;
                marker.GetPosition(out px, out py);
                map.projection.CoordinatesToTile(px, py, zoom, out px, out py);

                int k = j + 1;

                while (k < ms.Count)
                {
                    OnlineMapsMarker3D marker2 = ms[k];

                    double p2x, p2y;
                    marker2.GetPosition(out p2x, out p2y);
                    map.projection.CoordinatesToTile(p2x, p2y, zoom, out p2x, out p2y);

                    if (OnlineMapsUtils.SqrMagnitude(px, py, p2x, p2y) < sqrDist)
                    {
                        if (group == null)
                        {
                            group = new MarkerGroup(zoom, groupPrefab);
                            groups.Add(group);
                            group.Add(marker);
                            if (marker.range.min == 3) marker.range.min = zoom + 1;
                        }
                        group.Add(marker2);
                        if (marker2.range.min == 3) marker2.range.min = zoom + 1;
                        ms.RemoveAt(k);
                        px = group.tilePositionX;
                        py = group.tilePositionY;
                    }
                    else k++;
                }
            }
        }
    }

    internal class MarkerGroup
    {
        public readonly List<OnlineMapsMarker3D> markers;
        public readonly OnlineMapsMarker3D instance;

        public Vector2 center;
        public double tilePositionX, tilePositionY;

        public int zoom;

        public MarkerGroup(int zoom, GameObject prefab)
        {
            markers = new List<OnlineMapsMarker3D>();
            this.zoom = zoom;
            instance = OnlineMapsControlBase3D.instance.AddMarker3D(Vector2.zero, prefab);
            instance.range = new OnlineMapsRange(zoom, zoom);
        }

        public void Add(OnlineMapsMarker3D marker)
        {
            markers.Add(marker);
            center = markers.Aggregate(Vector2.zero, (current, m) => current + m.position) / markers.Count;
            instance.position = center;
            OnlineMaps.instance.projection.CoordinatesToTile(center.x, center.y, zoom, out tilePositionX, out tilePositionY);
            instance.label = "Group. Count: " + markers.Count;
        }
    }
}