private void editExistingBillboardAtlasToolStripMenuItem_Click(object sender, EventArgs e)
        {
            OpenFileDlg fileDlg = new OpenFileDlg();
              fileDlg.ShowBaseData = false;
              fileDlg.Caption = "Open existing Billboard Atlas file";
              fileDlg.Description = "Browse directories to open an existing texture atlas file. Then press OK to edit the atlas.";
              fileDlg.InitialDirectory = EditorManager.Project.ProjectDir;
              fileDlg.Filter = new string[] { ".atlas" };

              // start with selected model (if it is an .atlas file)
              if (TerrainEditor.CurrentDecorationModel != null && string.Compare(Path.GetExtension(TerrainEditor.CurrentDecorationModel.Filename), ".atlas", true) == 0)
            fileDlg.FileName = EditorManager.Project.MakeAbsolute(TerrainEditor.CurrentDecorationModel.Filename);

              if (fileDlg.ShowDialog() != DialogResult.OK)
            return;

              TextureAtlas atlas = TextureAtlas.CreateFromFile(EditorManager.Project.MakeRelative(fileDlg.FileName));
              if (atlas == null)
              {
            EditorManager.ShowMessageBox("Error loading atlas file", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            return;
              }

              TextureAtlasEditorDlg dlg = new TextureAtlasEditorDlg(true);
              dlg.Atlas = atlas;

              if (dlg.ShowDialog(this) != DialogResult.OK)
            return;
              dlg.Atlas.SaveToFile(null);
        }
        private void createNewBillboardAtlasToolStripMenuItem_Click(object sender, EventArgs e)
        {
            CreateFileDlg fileDlg = new CreateFileDlg();
              fileDlg.Caption = "Create a new Billboard Atlas file";
              fileDlg.Description = "Enter the name of the new atlas file and select the directory to create it in. Then press OK to continue.";
              fileDlg.InitialDirectory = EditorManager.Project.ProjectDir;
              fileDlg.Ext = ".atlas";
              fileDlg.AllowOverwrite = false;
              fileDlg.Filter = new string[] { ".atlas" };
              if (fileDlg.ShowDialog() != DialogResult.OK)
            return;

              TextureAtlas atlas = new TextureAtlas();
              atlas.Filename = EditorManager.Project.MakeRelative(fileDlg.FileName);
              TextureAtlasEditorDlg dlg = new TextureAtlasEditorDlg(true);
              dlg.Atlas = atlas;

              if (dlg.ShowDialog(this) != DialogResult.OK)
            return;
              dlg.Atlas.SaveToFile(null);
        }