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