-contents are dynamically updated if the mesh is modified.<br>
-To define a group, select in the Objet Browser or in the 3D viewer a
-geometrical object from which the elements will be taken. After
-confirmation of the operation a new group of mesh elements will be
-created.
+contents are dynamically updated if the mesh is modified. The group on
+geometry can be created only if the mesh is based on geometry.
+
+To define a group, click the \a Selection button and choose
+- <em>Direct geometry selection</em> to select a shape in the Object
+ Browser or in the Viewer;
+- <em>Find geometry by mesh element selection</em> to activate a
+ dialog which retrieves a shape by the selected element generated on
+ this shape.
+
+Note that this choice is available only if the mesh elements are
+already generated.