--- /dev/null
+.. _cutting_quadrangles_page:
+
+*******************
+Cutting quadrangles
+*******************
+
+This operation allows cutting one or several quadrangle elements into two or four triangles.
+
+*To cut quadrangles:*
+
+.. |img| image:: ../images/image82.png
+
+#. Select a mesh (and display it in the 3D Viewer if you are going to pick elements by mouse).
+#. In the **Modification** menu select the **Cutting of quadrangles** item or click *"Cutting of quadrangles"* button |img| in the toolbar.
+
+ The following dialog box will appear:
+
+ .. image:: ../images/a-cuttingofquadrangles.png
+ :align: center
+
+
+ * The main list contains the list of quadrangles selected for cutting. You can click on a quadrangle in the 3D viewer and it will be highlighted (lock Shift keyboard button to select several quadrangles):
+ * Click **Add** button and the ID of this quadrangle will be added to the list.
+ * To remove a selected element or elements from the list click **Remove** button.
+ * **Sort list** button allows sorting the list of IDs.
+ * **Filter** button allows applying a definite :ref:`filter <filtering_elements>` to the selection of quadrangles.
+ * **Apply to all** check box allows cutting all quadrangles of the selected mesh.
+ * **Preview** provides a preview of cutting in the viewer. It is disabled for **Cut into 4 triangles** as this cutting way implies no ambiguity.
+ * **Criterion** defines the way of cutting:
+ * **Cut into 4 triangles** allows cutting a quadrangle into four triangles by inserting a new node at the center of the quadrangle. The other options allow cutting a quadrangle into two triangles by connecting the nodes of a diagonal.
+ * **Use diagonal 1-3** and **Use diagonal 2-4** allow specifying the opposite corners, which will be connected to form two new triangles.
+ * **Use numeric functor** allows selecting in the field below a quality metric, which will be optimized when choosing a diagonal for cutting a quadrangle:
+ * **Minimum diagonal** cuts by the shortest diagonal.
+ * **Aspect Ratio** cuts by the diagonal splitting the quadrangle into triangles with :ref:`Aspect Ratio <aspect_ratio_page>` closer to 1
+ * **Minimum Angle** cuts by the diagonal splitting the quadrangle into triangles with :ref:`Minimum Angle <minimum_angle_page>` closer to 60 degrees.
+ * **Skew** cuts by the diagonal splitting the quadrangle into triangles with :ref:`Skew <skew_page>` closer to 0.0 degrees.
+ * **Select from** allows choosing a sub-mesh or an existing group, whose quadrangle elements then can be added to the main list.
+
+#. Click the **Apply** or **Apply and Close** button to confirm the operation.
+
+.. image:: ../images/image52.jpg
+ :align: center
+
+.. centered::
+ The chosen quadrangular element
+
+|
+
+.. image:: ../images/image51.jpg
+ :align: center
+
+.. centered::
+ Two resulting triangular elements
+
+**See Also** a sample TUI Script of a :ref:`tui_cutting_quadrangles` operation.
+
+
