doc new periodic commands

benchmarks/3d/CubePeriodic.geo

@@ -42,7 +42,7 @@ Volume (26) = {1000026};
 
 Physical Volume(1)={26};
 Physical Surface(10)={14:24:2};
-/*
+
 Periodic Line {4} = {2} ;
 Periodic Line {4} = {6} ;
 Periodic Line {4} = {8} ;
@@ -54,9 +54,10 @@ Periodic Line {1} = {3} ;
 Periodic Line {9} = {10} ;
 Periodic Line {9} = {11} ;
 Periodic Line {9} = {12} ;
-*/
+
 Periodic Surface 24 {1,2,3,4} = 16 {5,6,7,8};
 Periodic Surface 14 {10,5,9,1} = 22 {11,-7,12,-3};
 Periodic Surface 18 {9,8,12,4} = 20 {10,-6,11,-2};
+// TODO
 //Periodic Surface {14} = {22};
 //Periodic Surface {18} = {20};

doc/texinfo/gmsh.texi

@@ -1328,7 +1328,7 @@ evaluation:
 @c Built-in functions
 @c -------------------------------------------------------------------------
 
-@node Built-in functions, User-defined functions, Operators, General tools
+@node Built-in functions, User-defined macros, Operators, General tools
 @section Built-in functions
 
 @cindex Functions, built-in
@@ -1423,7 +1423,7 @@ Hyperbolic tangent of @var{expression}.
 @c -------------------------------------------------------------------------
 
 @node User-defined macros, Loops and conditionals, Built-in functions, General tools
-@section User-defined functions
+@section User-defined macros
 
 @cindex Macros, user-defined
 
@@ -2903,12 +2903,17 @@ the mesh of the surface.
 Force mesh of lines on the left-hand side (slaves) to match the mesh of
 the lines on the right-hand side (masters). 
 
-@item Periodic Surface @var{expression} @{ @var{expression-list} @} = @var{expression} @{ @var{expression-list} @} < Affine  @{ @var{expression-list} @} >;
+@item Periodic Surface @var{expression} @{ @var{expression-list} @} = @var{expression} @{ @var{expression-list} @} ;
 Force mesh of the surface on the left-hand side (slave, with boundary
 edges specified between braces) to match the mesh of the surface on the
-right-hand side (master, with boundary edges specified between braces). The
-optional @code{Affine} list specifies an explicit affine transform (as a 4 x 4
-matrix given by row).
+right-hand side (master, with boundary edges specified between braces).
+
+@item Periodic Line | Surface @{ @var{expression-list} @} = @{ @var{expression-list} @} Affine | Rotate | Translate @{ @var{expression-list} @} ;
+Force mesh of lines or surfaces on the left-hand side (slaves) to match
+the mesh of the lines on the right-hand side (masters), using prescribed
+geometrical transformations. @code{Affine} takes a 4 x 4 affine
+transform matrix given by row; @code{Rotate} and @code{Translate} are
+specified as in @ref{Transformations}.
 
 @item Coherence Mesh;
 Removes all duplicate mesh vertices.