CullingSystem

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;

//  Very simple, very stupid - but demonstrates a point about paying attention to real world data, not theoretical n^2
namespace CullingSystem
{
    class Program
    {

        static int pointCount = 1000;


        struct Vector3
        {
            public float x;
            public float y;
            public float z;

            public Vector3(float x, float y, float z)
            {
                this.x = x;
                this.y = y;
                this.z = z;
            }
            public Vector3(float randomDistance)
            {
                this.x = (float)rnd.NextDouble() * randomDistance;
                this.y = (float)rnd.NextDouble() * randomDistance;
                this.z = (float)rnd.NextDouble() * randomDistance;
            }

            public static Vector3 operator -(Vector3 a, Vector3 b)
            {
                return new Vector3(a.x - b.x, a.y - b.y, a.z - b.z);
            }

            public float sqrMagnitude()
            {
                return x * x + y * y + z * z;
            }
        }



        struct CullingData
        {
            public Vector3 position;
            public float sqrSight;

            public CullingData(Vector3 position, float sight)
            {
                this.position = position;
                this.sqrSight = sight * sight;
            }

        }
        static Random rnd = new Random();

        static void Main(string[] args)
        {
            while (true)
            {
                Console.ReadLine();

                var data = new CullingData[pointCount];

                for (int i = 0; i < pointCount; i++)
                    data[i] = new CullingData(new Vector3(1000), rnd.Next(50, 100));

                var sw = Stopwatch.StartNew();

                var pairs = new List<CullingData[]>();

                foreach (var point in data)
                    foreach (var opoint in data)
                        if ((point.position - opoint.position).sqrMagnitude() < point.sqrSight) pairs.Add(new[] { point, opoint });

                sw.Stop();

                Console.WriteLine("Time Elapsed: {0}ms, pairs found: " + pairs.Count, sw.ElapsedTicks * 1000f / Stopwatch.Frequency);
            }
        }
    }
}