private void FreeVegetationTile(VegetationTile tile)
 {
     if (tile != null)
     {
         tile.Dispose();
     }
 }
        private void NewCameraPage(PageCoord newPage)
        {
            if (enabled && TerrainManager.Instance.CameraSet)
            {
                // free the old vegetation tiles

                VegetationTile[,] newVegetationTiles = new VegetationTile[3, 3];
                if (vegetationTiles != null)
                {
                    foreach (VegetationTile tile in vegetationTiles)
                    {
                        PageCoord pc = tile.pc;
                        int       x  = pc.X - (newPage.X - 1);
                        int       z  = pc.Z - (newPage.Z - 1);
                        if ((x >= 0) && (x < 3) && (z >= 0) && (z < 3))
                        {
                            newVegetationTiles[x, z] = tile;
                        }
                        else
                        {
                            FreeVegetationTile(tile);
                        }
                    }
                }

                vegetationTiles = newVegetationTiles;

                for (int x = 0; x < 3; x++)
                {
                    for (int z = 0; z < 3; z++)
                    {
                        if (vegetationTiles[x, z] == null)
                        {
                            vegetationTiles[x, z] = new VegetationTile(parentSceneNode, vegetationBoundaries, x, z,
                                                                       newPage, blockSize,
                                                                       roadClearRadius, detailVegImageSet, rand);
                        }
                    }
                }

                cameraPage = newPage;
            }
        }