/*! \page split_to_tetra_page Splitting volumes \n This operation allows to split either any volumic elements into tetrahedra or hexahedra into prisms. 2D mesh is modified accordingly. <em>To split volumes:</em> <ol> <li>Display a mesh, a sub-mesh or a group in the 3D viewer.</li> <li>In the \b Modification menu select the <b>Split Volumes</b> item or click <em>"Split Volumes"</em> button in the toolbar. \image html split_into_tetra_icon.png <center><em>"Split Volumes" button</em></center> The following dialog box will appear: \image html split_into_tetra.png <br> <b>Target element type</b> group of radio-buttons allows to select a type of operation. If \b Tetrahedron button is checked, then the operation will split volumes of any type into tetrahedra. If \b Prism button is checked, then the operation will split hexahedra into prisms, and the dialog will look as follows: \image html split_into_prisms.png <ul> <li>The main list contains list of volumes to split. You can click on a volume in the 3D viewer and it will be highlighted (lock Shift keyboard button to select several volumes). Click \b Add button and the ID of this volume will be added to the list. To remove the 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 volumes. <br><b>Note:</b> If you split not all adjacent non-tetrahedral volumes, your mesh becomes non-conform.</li> <li><b>Apply to all</b> radio button allows to split all volumes of the currently selected mesh.</li> </ul> <ul> <li><b> Split hexahedron </b> group allows to specify a method of splitting hexahedra. <ul> <li><b>Into N tetrahedra/prisms</b> allows to specify the number of tetrahedra or prisms a hexahedron will be split into. If the specified method does not allow to get a conform mesh, a generic solution is applied: an additional node is created at the gravity center of a hexahedron, serving an apex of tetrahedra, all quadrangle sides of the hexahedron are split into two triangles each serving a base of a new tetrahedron.</li> <li> <b> Facet to split </b> group allows to specify a side (facet) of a hexahedron to split into triangles when splitting into prisms. The facet to split is defined by specifying a point and a direction close to normal of the facet. The operation finds a hexahedron most close to the specified point and splits a facet whose normal is most close to the specified direction. Then the splitting is propagated from that hexahedron to all adjacent hexahedra. <ul> <li> <b> Hexa location </b> allows to specify a <em> start point </em> by which a first split hexahedron is found. <em> Selection button</em> switches to selection of the element whose barycenter will be used the start point and whose direction will be used as a normal to facet to split into triangles. To return to selection of volumes to split it is necessary to switch this button off. </li> <li> <b> Facet normal </b> allows to specify a direction of the normal to hexahedron facet to split into triangles.</li> </ul> <li><b> All domains </b> - if it is off the operation stops as all hehexedra adjacent to the start hexahedron are split into prisms. Else the operation tries to continue splitting starting from another hexahedron closest to the <b> Hexa location</b>. </li> </li> </ul> <li><b>Select from</b> a set of fields allows to choose a sub-mesh or an existing group whose elements will be added to the list as you ckick \b Add button.</li> </ul> <li>Click the \b Apply or <b>Apply and Close</b> button to confirm the operation.</li> </ol> */