smesh/doc/salome/gui/SMESH/input/cutting_quadrangles.doc

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\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.  

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