-meshed source \b Face and the \b Mesh (optional, use it if there are several
-different meshes on the same face). It could also be necessary to
-define the orientation of mesh on the face, which is done by
-indicating two <b>Source Vertices</b>, which belong to the same edge of the
-source face, and two <b>Target Vertices</b>, which belong to the same edge of
-the created \b Face.
+meshed source \b Face and the \b Mesh (It can be omitted only when
+projecting a submesh on another one from the same global Mesh).
+It could also be necessary to define the orientation of mesh on the
+face, which is done by indicating two <b>Source Vertices</b>, which
+belong to the same edge of the source face, and two <b>Target
+Vertices</b>, which belong to the same edge of the created \b Face.
+For groups of face, they must contain equal number of faces
+and they must form topologically equal structures.
+
+\n <b>Projection 1D-2D</b> algorithm differs from <b>Projection 2D</b>
+algorithm in one aspect: it generates mesh segments on edges of
+the face according to the projected 2D elements; thus it does not
+require the edges to be meshed by any other 1D algorithm; moreover it
+does not allow to mesh edges of the face using another algorithm via
+definition of sub-meshes.