--- /dev/null
+.. _merging_nodes_page:
+
+*************
+Merging nodes
+*************
+
+This functionality allows user to detect groups of coincident nodes with specified tolerance; each group of the coincident nodes can be then converted to the single node.
+
+.. image:: ../images/mergenodes_ico.png
+ :align: center
+
+.. centered::
+ *"Merge nodes"* menu button
+
+.. |ad| image:: ../images/add.png
+.. |rm| image:: ../images/remove.png
+.. |mv| image:: ../images/sort.png
+
+*To merge nodes of your mesh:*
+
+#. Choose **Modification** -> **Transformation** -> **Merge nodes** menu item. The following dialog box shall appear:
+
+ .. image:: ../images/mergenodes_auto.png
+ :align: center
+
+ * **Names** contains names of the selected mesh objects whose nodes will be merged.
+ * **Automatic** or **Manual** mode allows choosing how the nodes are processed. In **Manual** mode you can adjust groups of coincident nodes detected by the program and/or select any nodes to be merged.
+ * **Tolerance** is a maximum distance between nodes sufficient for merging.
+ * Activation of **No merge of corner and medium nodes of quadratic cells** check-box prevents merging medium nodes of quadratic elements with corner nodes. This check-box is enabled provided that the selected mesh includes quadratic elements.
+ * Activation of **Avoid making holes** check-box prevents merging nodes that make elements invalid (but not degenerated) and hence removed. Thus, no holes in place of removed elements appear.
+ * **Exclude groups from detection** group allows to ignore the nodes which belong to the specified mesh groups. This control is active provided that the mesh includes groups.
+ * **Nodes to keep during the merge** group allows to specify nodes to keep in the mesh. (By default a node being the first in a group of coincident nodes is kept.) It is possible to either select nodes in the Viewer or select groups of any element type whose nodes will be kept.
+
+ * *Selection* button activates selection of nodes to keep.
+ * **Nodes** button activates selection of nodes in the Viewer.
+ * **Groups and sub-meshes** button activates selection of groups and sub-meshes.
+ * **Add** button adds selected nodes or groups to the list.
+ * Nodes or groups selected in the list can be removed using **Remove** button.
+
+#. **Automatic mode:**
+
+ * In the **Automatic** Mode all nodes within the indicated tolerance will be merged. The nodes which belong to the groups specified in **Exclude groups from detection** will NOT be taken into account.
+
+#. The **Manual** mode gives you full control of what the operation will do. In this mode additional controls are available:
+
+ * **Detect** button generates the list of coincident nodes for the given **Tolerance**.
+ * **Coincident nodes** is a list of groups of nodes for merging. Upon **Apply** all nodes of each group will be united into one node. The first node of a group is kept and the others are removed. By default the first node has a lowest ID within the group.
+
+ * **Remove** button deletes the selected group from the list.
+ * **Add** button adds to the list a group of nodes selected in the viewer.
+ * **Select all** check-box selects all groups.
+ * **Show double nodes IDs** check-box shows/hides identifiers of nodes of selected groups in the 3D viewer.
+
+ .. image:: ../images/mergenodes.png
+ :align: center
+
+
+ * **Edit selected group of coincident nodes** list allows editing the selected group:
+
+ * |ad| adds to the group the nodes selected in the viewer.
+ * |rm| removes from the group the selected nodes.
+ * |mv| moves the selected node to the first position in the group in order to keep it in the mesh.
+
+#. To confirm your choice click **Apply** or **Apply and Close** button.
+
+.. figure:: ../images/merging_nodes1.png
+ :align: center
+
+ The initial object. Nodes 25, 26 and 5 are added to **Nodes to keep during the merge** group.
+
+.. figure:: ../images/merging_nodes2.png
+ :align: center
+
+ The object has been merged
+
+
+**See Also** a sample TUI Script of a :ref:`tui_merging_nodes` operation.
+
+