diff --git a/CustomWidgets/TreeView/TreeNode.cs b/CustomWidgets/TreeView/TreeNode.cs
index d0acfd609..02a355d65 100644
--- a/CustomWidgets/TreeView/TreeNode.cs
+++ b/CustomWidgets/TreeView/TreeNode.cs
@@ -378,7 +378,14 @@ namespace MatterHackers.MatterControl.CustomWidgets.TreeView
 		//     A TreeView that represents the parent tree view that the
 		//     tree node is assigned to, or null if the node has not been assigned to a tree
 		//     view.
-		public virtual TreeView TreeView => NodeParent.TreeView;
+
+		private TreeView _treeView;
+
+		public virtual TreeView TreeView
+		{
+			get => _treeView ?? NodeParent.TreeView;
+			set => _treeView = value;
+		}
 
 		private void OnImageChanged(EventArgs args)
 		{
diff --git a/CustomWidgets/TreeView/TreeView.cs b/CustomWidgets/TreeView/TreeView.cs
index 8c7e36526..f3c98cfea 100644
--- a/CustomWidgets/TreeView/TreeView.cs
+++ b/CustomWidgets/TreeView/TreeView.cs
@@ -36,33 +36,22 @@ using MatterHackers.VectorMath;
 
 namespace MatterHackers.MatterControl.CustomWidgets.TreeView
 {
-	public class TopNode : TreeNode
-	{
-		internal TreeView treeView;
-		public override TreeView TreeView => treeView;
-	}
-
 	public class TreeView : ScrollableWidget
 	{
 		private ThemeConfig theme;
 
-		public TreeView(TopNode topNode, ThemeConfig theme)
-			: this(topNode, 0, 0, theme)
+		public TreeView(ThemeConfig theme)
+			: this(0, 0, theme)
 		{
 		}
 
-		public TreeView(TopNode topNode, int width, int height, ThemeConfig theme)
+		public TreeView(int width, int height, ThemeConfig theme)
 			: base(width, height)
 		{
 			this.theme = theme;
 			this.AutoScroll = true;
 			this.HAnchor = HAnchor.Stretch;
 			this.VAnchor = VAnchor.Stretch;
-			this.TopNode = topNode;
-
-			topNode.treeView = this;
-
-			this.AddChild(TopNode);
 		}
 
 		#region Events
@@ -230,7 +219,6 @@ namespace MatterHackers.MatterControl.CustomWidgets.TreeView
 		public bool ShowPlusMinus { get; set; }
 		public bool ShowRootLines { get; set; }
 		public bool Sorted { get; set; }
-		public TreeNode TopNode { get; }
 
 		public IComparer TreeViewNodeSorter { get; set; }
 
diff --git a/PartPreviewWindow/Object3DTreeBuilder.cs b/PartPreviewWindow/Object3DTreeBuilder.cs
index 79bd12bbb..2edfad8e2 100644
--- a/PartPreviewWindow/Object3DTreeBuilder.cs
+++ b/PartPreviewWindow/Object3DTreeBuilder.cs
@@ -31,6 +31,7 @@ using MatterHackers.Agg.UI;
 using MatterHackers.DataConverters3D;
 using MatterHackers.MatterControl.CustomWidgets;
 using MatterHackers.MatterControl.CustomWidgets.TreeView;
+using MatterHackers.MatterControl.DesignTools;
 using MatterHackers.MatterControl.Library;
 using MatterHackers.MatterControl.PartPreviewWindow.View3D;
 
@@ -38,39 +39,12 @@ namespace MatterHackers.MatterControl.PartPreviewWindow
 {
 	public static class Object3DTreeBuilder
 	{
-		public static TreeView GetPartTreeView(IObject3D rootItem, ThemeConfig theme)
+		public static TreeNode BuildTree(IObject3D rootItem, ThemeConfig theme)
 		{
-			var topNode = new TopNode()
-			{
-				Text = BuildDefaultName(rootItem),
-				Tag = rootItem,
-				TextColor = theme.Colors.PrimaryTextColor,
-				PointSize = theme.DefaultFontSize
-			};
-
-			var treeView = new TreeView(topNode, theme)
-			{
-				TextColor = theme.Colors.PrimaryTextColor,
-				PointSize = theme.DefaultFontSize
-			};
-
-			treeView.SuspendLayout();
-
-			//selectionTreeNodes.Clear();
-			//selectionTreeNodes.Add(rootItem, topNode);
-
-			// add the children to the root node
-			foreach (var child in rootItem.Children)
-			{
-				AddTree(child, topNode, theme);
-			}
-
-			treeView.ResumeLayout();
-
-			return treeView;
+			return AddTree(rootItem, null, theme);
 		}
 
-		private static void AddTree(IObject3D item, TreeNode parent, ThemeConfig theme)
+		private static TreeNode AddTree(IObject3D item, TreeNode parent, ThemeConfig theme)
 		{
 			// Suppress MeshWrapper nodes in treeview - retain parent node as context reference
 			var contextNode = (item is MeshWrapper) ? parent : AddItem(item, parent, theme);
@@ -79,6 +53,8 @@ namespace MatterHackers.MatterControl.PartPreviewWindow
 			{
 				AddTree(child, contextNode, theme);
 			}
+
+			return contextNode;
 		}
 
 		private static TreeNode AddItem(IObject3D item, TreeNode parentNode, ThemeConfig theme)
@@ -115,8 +91,11 @@ namespace MatterHackers.MatterControl.PartPreviewWindow
 				};
 			}
 
-			parentNode.Nodes.Add(node);
-			parentNode.Expanded = true;
+			if (parentNode != null)
+			{
+				parentNode.Nodes.Add(node);
+				parentNode.Expanded = true;
+			}
 
 			return node;
 		}
diff --git a/PartPreviewWindow/View3D/View3DWidget.cs b/PartPreviewWindow/View3D/View3DWidget.cs
index 3c73cef96..38a457e37 100644
--- a/PartPreviewWindow/View3D/View3DWidget.cs
+++ b/PartPreviewWindow/View3D/View3DWidget.cs
@@ -192,7 +192,18 @@ namespace MatterHackers.MatterControl.PartPreviewWindow
 			modelViewSidePanel.AddChild(treeSection);
 
 			// add the tree view
-			this.RebuildTreeSection(new Object3D(), theme);
+			treeView = new TreeView(theme)
+			{
+				TextColor = theme.Colors.PrimaryTextColor,
+				PointSize = theme.DefaultFontSize,
+				HAnchor =HAnchor.Stretch,
+				VAnchor = VAnchor.Stretch
+			};
+			treeView.AfterSelect += (s, e) =>
+			{
+				selectedObjectPanel.SetActiveItem((IObject3D)treeView.SelectedNode.Tag);
+			};
+			treeSection.AddChild(treeView);
 
 			modelViewSidePanel.AddChild(selectedObjectPanel);
 			splitContainer.AddChild(modelViewSidePanel);
@@ -236,24 +247,6 @@ namespace MatterHackers.MatterControl.PartPreviewWindow
 			}
 		}
 
-		private void RebuildTreeSection(IObject3D selection, ThemeConfig theme)
-		{
-			treeSection.CloseAllChildren();
-
-			treeView = Object3DTreeBuilder.GetPartTreeView(selection, theme);
-			treeSection.AddChild(treeView);
-			treeView.AfterSelect += (s, e) =>
-			{
-				selectedObjectPanel.SetActiveItem((IObject3D)treeView.SelectedNode.Tag);
-			};
-
-			if (this.Parent != null)
-			{
-				treeView.TopNode.Padding = treeView.TopNode.Padding.Clone(left: 8, top: 8);
-				treeView.SelectedNode = treeView.TopNode;
-			}
-		}
-
 		private void UpdateRenderView(object sender, EventArgs e)
 		{
 			TrackballTumbleWidget.CenterOffsetX  = -modelViewSidePanel.Width;
@@ -1222,9 +1215,20 @@ namespace MatterHackers.MatterControl.PartPreviewWindow
 			}
 
 			// Top level selection only - rebuild tree
-			if (Scene.Children.Contains(Scene.SelectedItem))
+			var selection = Scene.SelectedItem;
+			if (Scene.Children.Contains(selection))
 			{
-				this.RebuildTreeSection(Scene.SelectedItem, theme);
+				treeView.ScrollArea.CloseAllChildren();
+
+				var rootNode = Object3DTreeBuilder.BuildTree(selection, theme);
+				treeView.AddChild(rootNode);
+				rootNode.TreeView = treeView;
+
+				if (this.Parent != null)
+				{
+					rootNode.Padding = rootNode.Padding.Clone(left: 8, top: 8);
+					treeView.SelectedNode = rootNode;
+				}
 			}
 		}
 
diff --git a/Submodules/agg-sharp b/Submodules/agg-sharp
index a38d5e68b..21532f82c 160000
--- a/Submodules/agg-sharp
+++ b/Submodules/agg-sharp
@@ -1 +1 @@
-Subproject commit a38d5e68bcaace904d1dc18e416ea9ace6756ac2
+Subproject commit 21532f82c733e0adc9db8b82f2f10cb66b60ed52