+<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