Sample C# code for indexing a series of polygon vertices using Z-order. In order to compile this code, download and reference NetTopologySuite, an open source spatial analysis library.

gistfile1.cs

using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using GeoAPI.Geometries;
using NetTopologySuite.Geometries;
using NetTopologySuite.IO;
using NetTopologySuite.Densify;

namespace MortonOrder
{
  class MainClass
  {
    public struct IndexablePoint
    {
      public IGeometry Point;
      public long ZValue;

      public IndexablePoint (IGeometry point, long zvalue)
      {
        Point = point;
        ZValue = zvalue;
      }
    }
    
    public static void Main (string[] args)
    {
      IGeometryFactory gfactory = GeometryFactory.Fixed;
      WKTReader greader = new WKTReader (gfactory);
      //Polygon instance from WKT
      IGeometry building = greader.Read ("POLYGON((0 0, 0 5, 10 5, 10 1, 2 1, 2 0, 0 0))");
      //Densify polygon
      IGeometry densification = Densifier.Densify (building, 1);
      IndexablePoint[] points = new IndexablePoint[densification.NumPoints - 1];
      //Calculate and store z-values using bit interleaving
      for (int i = 0; i <= points.GetUpperBound (0); i++) {
        IGeometry point = gfactory.CreatePoint (densification.Coordinates[i]);
        uint x = (uint) point.Coordinate.X;
        uint y = (uint) point.Coordinate.Y;
        long zvalue = GetZValue (x, y);
        points[i] = new IndexablePoint (point, zvalue);
      }
    }
    
    //Generate a 64bit integer by bit interleaving a pair of 32bit unsigned integers
    //representing a coordinate value. Resulting integer can be stored as a one-dimensional
    //sortable key in an index which preserves spatial proximity.
    static long GetZValue(uint x32, uint y32)
    {
      byte[] x32bytes = BitConverter.GetBytes(x32);
      byte[] y32bytes = BitConverter.GetBytes(y32);
      BitArray xba = new BitArray(x32bytes);
      BitArray yba = new BitArray(y32bytes);
      BitArray zba = new BitArray(64);
      for (int i = 0; i < 32; i++) {
        if (xba[i]) zba.Set(2 * i, true);
        if (yba[i]) zba.Set((2 * i) + 1, true);
      }
      byte[] zbytes = new byte[8];
      zba.CopyTo(zbytes, 0);
      return BitConverter.ToInt64(zbytes, 0);
    }
  }
}