\page cutting_quadrangles_page Cutting quadrangles
-\n This operation allows to cut one or several quadrangle elements by
-addition of a supplementary edge which will connect two opposite
-corners.
+\n This operation allows cutting one or several quadrangle elements
+into two or four triangles.
<em>To cut quadrangles:</em>
<ol>
-<li>Display a mesh or a sub-mesh in the 3D viewer.</li>
+<li>Display a mesh, a 2D sub-mesh or a group of faces in the 3D viewer.</li>
<li>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 a-cuttingofquadrangles.png
-\par
<ul>
-<li>The main list contains the list of quadrangles. You can click on
-an 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 to sort the list of IDs. \b Filter button allows to
-apply a definite filter to the selection of quadrangles.</li>
-<li><b>Apply to all</b> check box allows to modify the orientation of all
-quadrangles of the currently displayed mesh or sub-mesh.</li>
-<li>\b Preview - provides a preview of cutting in the viewer.</li>
+<li>The main list contains the list of quadrangles selected for cutting. You can
+ click on an 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 to sort the
+ list of IDs. \b Filter button allows to apply a definite filter to the selection of
+ quadrangles.</li>
+<li><b>Apply to all</b> check box allows to cut all quadrangles of the selected mesh,
+ sub-mesh or group.</li>
+<li>\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.</li>
</ul>
<ul>
-<li>\b Criterion
+<li>\b Criterion defines a cutting way.
<ul>
-<li><b>Use diagonal 1-3</b> and <b>Use diagonal 2-4</b> allows to
-specify the opposite corners which will be connected by the cutting
-edge.</li>
-<li><b>Use numeric functor</b> - allows to choose a quality criterion
- which will be optimized at the outcome of the operation.
-<ul>
-<li><b>Minimum diagonal</b> - cuts by the shortest edge.</li>
-<li><b>Aspect Ratio</b> - cuts by the edge splitting the quadrangle
-into triangles with optimal \ref aspect_ratio_page "Aspect Ratio". The reference value is 1.</li>
-<li><b>Minimum Angle</b> - cuts by the edge splitting the quadrangle
-into triangles with optimal \ref minimum_angle_page "Minimum Angle". The reference value is 60 degrees.</li>
-<li><b>Skew</b> - cuts by the edge splitting the quadrangle
-into triangles with optimal \ref skew_page "Skew". The reference value
-is 0.0 degrees.</li>
-</ul>
+<li><b>Cut into 4 triangles</b> selects cutting the quadrangle into four triangles by
+ inserting a new node at the center of quadrangle. The other options selects cutting
+ the quadrangle into two triangles by connecting nodes of either of the two diagonals.
+<li><b>Use diagonal 1-3</b> and <b>Use diagonal 2-4</b> allows to specify the
+ opposite corners which will be connected to form two new triangles.</li>
+<li><b>Use numeric functor</b> allows to choose a quality metric which will be
+ optimized when choosing a diagonal for cutting a quadrangle.
+ <ul>
+ <li><b>Minimum diagonal</b> cuts by the shortest diagonal.</li>
+ <li><b>Aspect Ratio</b> cuts by the diagonal splitting the quadrangle into
+ triangles with \ref aspect_ratio_page "Aspect Ratio" closer to 1.</li>
+ <li><b>Minimum Angle</b> cuts by the diagonal splitting the quadrangle into
+ triangles with \ref minimum_angle_page "Minimum Angle" closer to 60
+ degrees.</li>
+ <li><b>Skew</b> cuts by the diagonal splitting the quadrangle into triangles
+ with \ref skew_page "Skew" closer to 0.0 degrees.</li>
+ </ul>
</li>
</ul>
</li>
-<li><b>Select from</b> - allows to choose a sub-mesh or an existing
-group whose quadrangle elements will be automatically added to the
-list.</li>
+<li><b>Select from</b> allows to choose a sub-mesh or an existing group whose
+ quadrangle elements will be automatically added to the main list.</li>
</ul>
</li>
