\image html viscous_layers_hyp.png
+\image html viscous_layers_2d_hyp.png
+
<ul>
<li><b>Name</b> - allows to define the name of the hypothesis.</li>
<li><b>Total thickness</b> - gives the total thickness of element layers.</li>
<li><b>Number of layers</b> - defines the number of element layers.</li>
<li><b>Stretch factor</b> - defines the growth factor of element height
from the mesh boundary inwards.</li>
+<li><b>Extrusion method</b> (available in 3D only) - defines how
+ position of nodes are found during prism construction and how
+ creation of distorted and intersecting prisms is prevented.
+<ul><li><b>Surface offset + smooth</b> method extrudes nodes along normal
+ to underlying geometrical surface. Smoothing of internal surface of
+ element layers is possible to avoid creation of invalid prisms.</li>
+ <li><b>Face offset</b> method extrudes nodes along average normal of
+ surrounding mesh faces till intersection with a neighbor mesh face
+ translated along its own normal by the layers thickness. Thickness
+ of layers can be limited to avoid creation of invalid prisms.</li>
+ <li><b>Node offset</b> method extrudes nodes along average normal of
+ surrounding mesh faces by the layers thickness. Thickness of
+ layers can be limited to avoid creation of invalid prisms.</li>
+\image html viscous_layers_extrusion_method.png "Prisms created by the tree extrusion methods at the same other parameters"
+</ul></li>
<li><b>Specified Faces/Edges are</b> - defines how the shapes specified by
the next parameter are used.
<li><b> Faces/Edges with/without layers</b> -
Faces (or edges) can be selected either in the Object Browser or in
the VTK Viewer.
\note A mesh shown in the 3D Viewer can prevent selection of faces
- and edges, just hide the mesh to avoid this. To avoid a long wait when a
+ and edges, just hide the mesh to avoid this. Sometimes a face to
+ select is hidden by other faces, in this case consider creating a
+ group of faces you want to select in the Geometry module.<br>
+ To avoid a long wait when a
geometry with many faces (or edges) is displayed, the number of faces
(edges) shown at a time is limited by the value of "Sub-shapes
preview chunk size" preference (in Preferences/Mesh/General tab).
+
If faces/edges without layers are specified, the element layers are
not constructed on geometrical faces shared by several solids in 3D
case and edges shared by several faces in 2D case. In other words,
