--- a/NEWS	Thu Apr 19 16:26:56 2012 -0400
+++ b/NEWS	Thu Apr 19 17:44:46 2012 -0400
@@ -63,7 +63,7 @@
 
       colorcube   splinefit
       lines       tetramesh
-      rgbplot
+      rgbplot     shrinkfaces
 
  ** Deprecated functions.
 

--- a/doc/interpreter/plot.txi	Thu Apr 19 16:26:56 2012 -0400
+++ b/doc/interpreter/plot.txi	Thu Apr 19 17:44:46 2012 -0400
@@ -363,6 +363,8 @@
 
 @DOCSTRING(isocolors)
 
+@DOCSTRING(shrinkfaces)
+
 @DOCSTRING(diffuse)
 
 @DOCSTRING(specular)

--- a/scripts/help/unimplemented.m	Thu Apr 19 16:26:56 2012 -0400
+++ b/scripts/help/unimplemented.m	Thu Apr 19 17:44:46 2012 -0400
@@ -339,7 +339,6 @@
   "serial",
   "setpixelposition",
   "showplottool",
-  "shrinkfaces",
   "smooth3",
   "snapnow",
   "sound",

--- a/scripts/plot/module.mk	Thu Apr 19 16:26:56 2012 -0400
+++ b/scripts/plot/module.mk	Thu Apr 19 17:44:46 2012 -0400
@@ -162,6 +162,7 @@
   plot/semilogyerr.m \
   plot/shading.m \
   plot/shg.m \
+  plot/shrinkfaces.m \
   plot/slice.m \
   plot/sombrero.m \
   plot/specular.m \

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/scripts/plot/shrinkfaces.m	Thu Apr 19 17:44:46 2012 -0400
@@ -0,0 +1,215 @@
+## Copyright (C) 2012 Martin Helm
+##
+## This file is part of Octave.
+##
+## Octave is free software; you can redistribute it and/or modify it
+## under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 3 of the License, or (at
+## your option) any later version.
+##
+## Octave is distributed in the hope that it will be useful, but
+## WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+## General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with Octave; see the file COPYING.  If not, see
+## <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {} shrinkfaces (@var{p}, @var{sf})
+## @deftypefnx {Function File} {@var{nfv} =} shrinkfaces (@var{p}, @var{sf})
+## @deftypefnx {Function File} {@var{nfv} =} shrinkfaces (@var{fv}, @var{sf})
+## @deftypefnx {Function File} {@var{nfv} =} shrinkfaces (@var{f}, @var{v}, @var{sf})
+## @deftypefnx {Function File} {[@var{nf}, @var{nv}] =} shrinkfaces (@dots{})
+##
+## Reduce the faces area for a given patch, structure or explicit faces
+## and points matrices by a scale factor @var{sf}.  The structure
+## @var{fv} must contain the fields 'faces' and 'vertices'.  If the
+## factor @var{sf} is omitted then a default of 0.3 is used.
+##
+## Given a patch handle as the first input argument and no output
+## parameters, perform the shrinking of the patch faces in place and
+## redraw the patch.
+##
+## If called with one output argument, return a structure with fields
+## 'faces', 'vertices', and 'facevertexcdata' containing the data after
+## shrinking which can then directly be used as an input argument for the
+## @command{patch} function.
+##
+## Performing the shrinking on faces which are not convex can lead to
+## undesired results.
+##
+## For example
+##
+## @example
+## @group
+## [phi r] = meshgrid (linspace (0, 1.5*pi, 16), linspace (1, 2, 4));
+## tri = delaunay (phi(:), r(:));
+## v = [r(:).*sin(phi(:)) r(:).*cos(phi(:))];
+## clf ()
+## p = patch ("Faces", tri, "Vertices", v, "FaceColor", "none");
+## fv = shrinkfaces (p);
+## patch (fv)
+## axis equal
+## grid on
+## @end group
+## @end example
+##
+## @noindent
+## draws a triangulated 3/4 circle and the corresponding shrinked
+## version.
+## @seealso{patch}
+## @end deftypefn
+
+## Author: Martin Helm <martin@mhelm.de>
+
+function [nf, nv] = shrinkfaces (varargin)
+
+  if (nargin < 1 || nargin > 3 || nargout > 2)
+    print_usage ();
+  endif
+  
+  sf = 0.3;
+  p = varargin{1};
+  colors = [];
+
+  if (ishandle (p) && nargin < 3)
+    faces = get (p, "Faces");
+    vertices = get (p, "Vertices");
+    colors = get (p, "FaceVertexCData");
+    if (nargin == 2)
+      sf = varargin{2};
+    endif
+  elseif (isstruct (p) && nargin < 3)
+    faces = p.faces;
+    vertices = p.vertices;
+    if (isfield (p, "facevertexcdata"))
+      colors = p.facevertexcdata;
+    endif
+    if (nargin == 2)
+      sf = varargin{2};
+    endif
+  elseif (ismatrix (p) && nargin >= 2 && ismatrix (varargin{2}))
+    faces = p;
+    vertices = varargin{2};
+    if (nargin == 3)
+      sf = varargin{3};
+    endif
+  else
+    print_usage ();
+  endif
+  
+  if (! isscalar (sf) || sf <= 0)
+    error ("shrinkfaces: scale factor must be a positive scalar")
+  endif
+
+  n = size (vertices, 2);
+  if (n < 2 || n > 3)
+    error ("shrinkfaces: only 2D and 3D patches are supported")
+  endif
+
+  m = size (faces, 2);
+  if (m < 3)
+    error ("shrinkfaces: faces must consist of at least 3 vertices")
+  endif
+
+  v = vertices(faces'(:), :);
+  if (isempty (colors) || size (colors, 1) == size (faces, 1))
+    c = colors;
+  elseif (size (colors, 1) == size (vertices, 1))
+    c = colors(faces'(:), :);
+  else
+    ## Discard inconsistent color data.
+    c = [];
+  endif
+  sv = size (v, 1);
+  ## we have to deal with a probably very large number of vertices, so
+  ## use sparse we use as midpoint (1/m, ..., 1/m) in generalized
+  ## barycentric coordinates.
+  midpoints = full (kron ( speye (sv / m), ones (m, m) / m) * sparse (v));
+  v = sqrt (sf) * (v - midpoints) + midpoints;
+  f = reshape (1:sv, m, sv / m)';
+  
+  switch (nargout)
+    case 0
+      if (ishandle (p))
+        set (p, "FaceVertexCData", [], "CData", []) # avoid exceptions
+        set (p, "Vertices", v, "Faces", f, "FaceVertexCData", c)
+      else
+        nf = struct ("faces", f, "vertices", v, "facevertexcdata", c);
+      endif
+    case 1
+      nf = struct ("faces", f, "vertices", v, "facevertexcdata", c);
+    case 2
+      nf = f;
+      nv = v;
+  endswitch
+
+endfunction
+
+%!demo
+%! faces = [1 2 3; 1 3 4];
+%! vertices = [0 0; 1 0; 1 1; 0 1];
+%! clf ()
+%! patch ("Faces", faces, "Vertices", vertices, "FaceColor", "none")
+%! fv = shrinkfaces (faces, vertices, 0.25);
+%! patch (fv)
+%! axis equal
+
+%!demo
+%! faces = [1 2 3 4; 5 6 7 8];
+%! vertices = [0 0; 1 0; 2 1; 1 1; 2 0; 3 0; 4 1; 3.5 1];
+%! clf ()
+%! patch ("Faces", faces, "Vertices", vertices, "FaceColor", "none")
+%! fv = shrinkfaces (faces, vertices, 0.25);
+%! patch (fv)
+%! axis equal
+%! grid on
+
+%!demo
+%! faces = [1 2 3 4];
+%! vertices = [-1 2; 0 0; 1 2; 0 1];
+%! clf ()
+%! patch ("Faces", faces, "Vertices", vertices, "FaceColor", "none")
+%! fv = shrinkfaces (faces, vertices, 0.25);
+%! patch (fv)
+%! axis equal
+%! grid on
+%! title "faces which are not convex are clearly not allowed"
+
+%!demo
+%! [phi r] = meshgrid (linspace (0, 1.5*pi, 16), linspace (1, 2, 4));
+%! tri = delaunay (phi(:), r(:));
+%! v = [r(:).*sin(phi(:)) r(:).*cos(phi(:))];
+%! clf ()
+%! p = patch ("Faces", tri, "Vertices", v, "FaceColor", "none");
+%! fv = shrinkfaces (p);
+%! patch (fv)
+%! axis equal
+%! grid on
+
+%!demo
+%! N = 10; # N intervals per axis
+%! [x, y, z] = meshgrid (linspace (-4,4,N+1));
+%! val = x.^3 + y.^3 + z.^3;
+%! fv = isosurface (x, y, z, val, 3, z);
+%!
+%! clf ()
+%! p = patch ("Faces", fv.faces, "Vertices", fv.vertices, "FaceVertexCData", ...
+%!            fv.facevertexcdata, "FaceColor", "interp", "EdgeColor", "black");
+%! axis equal
+%! view (115, 30)
+%! drawnow
+%! shrinkfaces (p, 0.6);
+
+%!shared faces, vertices, nfv, nfv2
+%! faces = [1 2 3];
+%! vertices = [0 0 0; 1 0 0; 1 1 0];
+%! nfv = shrinkfaces (faces, vertices, 0.7);
+%! nfv2 = shrinkfaces (nfv, 1/0.7);
+%!assert (isfield (nfv, "faces"));
+%!assert (isfield (nfv, "vertices"));
+%!assert (size (nfv.faces), [1 3]);
+%!assert (size (nfv.vertices), [3 3]);
+%!assert (norm (nfv2.vertices - vertices), 0, 2*eps);