XNA i znikające powierzchnie

 
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;

namespace XNA_First_Person_Camera
{
    class Floor
    {
        //Atrybuty - Attributes
        private int floorWidth;
        private int floorHeight;
        private VertexBuffer floorBuffer;
        private GraphicsDevice device;
        private Color[] floorColors = new Color[2] { Color.White, Color.Black };
        //Konstruktor
        public Floor(GraphicsDevice device, int width, int height)
        {
            this.device = device;
            this.floorWidth = width;
            this.floorHeight = height;
            BuildFloorBuffer();
        }
        //Buduje Vertex Buffer
        private void BuildFloorBuffer()
        {
            List<VertexPositionColor> vertexList = new List<VertexPositionColor>();
            int counter = 0;
            //Pętla tworząca podłoge
            for (int x = 0; x < floorWidth; x++)
            {
                counter++;
                for (int z = 0; z < floorHeight; z++)
                {
                    counter++;

                    //Pętla tworząca wierzchołki
                    foreach (VertexPositionColor vertex in FloorTile(x, z, floorColors[counter % 2]))
                    {
                        vertexList.Add(vertex);
                    }
                }
            }
            //Tworzy Buffer
            floorBuffer = new VertexBuffer(device,VertexPositionColor.VertexDeclaration,vertexList.Count,BufferUsage.None);
            floorBuffer.SetData<VertexPositionColor>(vertexList.ToArray());
        }
        //Definiuje pojedyńczą komórkę w naszej podłodze
        private List<VertexPositionColor> FloorTile(int xOffset, int zOffset, Color TileColor)
        {
            List<VertexPositionColor> vList = new List<VertexPositionColor>();
            vList.Add(new VertexPositionColor(new Vector3(0 + xOffset, 0, 0 + zOffset), TileColor));
            vList.Add(new VertexPositionColor(new Vector3(1 + xOffset, 0, 0 + zOffset), TileColor));
            vList.Add(new VertexPositionColor(new Vector3(0 + xOffset, 0, 1 + zOffset), TileColor));
            vList.Add(new VertexPositionColor(new Vector3(1 + xOffset, 0, 0 + zOffset), TileColor));
            vList.Add(new VertexPositionColor(new Vector3(1 + xOffset, 0, 1 + zOffset), TileColor));
            vList.Add(new VertexPositionColor(new Vector3(0 + xOffset, 0, 1 + zOffset), TileColor));
            return vList;
        }
        //Metoda rysująca
        public void Draw(Camera camera, BasicEffect effect)
        {
            effect.VertexColorEnabled = true;
            effect.View = camera.View;
            effect.Projection = camera.Projection;
            effect.World = Matrix.Identity;

            //Pętla rysująca Wierzchołki
            foreach (EffectPass pass in effect.CurrentTechnique.Passes)
            {
                pass.Apply();
                device.SetVertexBuffer(floorBuffer);
                device.DrawPrimitives(PrimitiveType.TriangleList, 0, floorBuffer.VertexCount / 3 );
            }
        }
    }
}