# HG changeset patch
# User Martin Helm <martin@mhelm.de>
# Date 1333409671 14400
# Node ID 34a9fdaa6ea32fab08d1a39b89d716be65474971
# Parent  3313635c622d3672ef58af075a1d879d13af0e37
New Function, tetramesh.m

* tetramesh.m: New File.
* scripts/plot/module.mk: Add new file.

diff --git a/scripts/plot/module.mk b/scripts/plot/module.mk
--- a/scripts/plot/module.mk
+++ b/scripts/plot/module.mk
@@ -175,6 +175,7 @@
   plot/surfc.m \
   plot/surfl.m \
   plot/surfnorm.m \
+  plot/tetramesh.m \
   plot/text.m \
   plot/title.m \
   plot/trimesh.m \
diff --git a/scripts/plot/tetramesh.m b/scripts/plot/tetramesh.m
new file mode 100644
--- /dev/null
+++ b/scripts/plot/tetramesh.m
@@ -0,0 +1,161 @@
+## 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} tetramesh (@var{T}, @var{X})
+## @deftypefnx {Function File} tetramesh (@var{T}, @var{X}, @var{C})
+## @deftypefnx {Function File} {[@var{h}] =} tetramesh (...)
+## @deftypefnx {Function File} {[@var{h}] =} tetramesh (..., @var{PROP}, @var{VAL})
+##
+## The function displays the tetrahedrons defined in the m by 4 matrix @var{T}
+## as 3D patches. @var{T} is usually the output of a Delaunay triangulation of a
+## 3D set of points. 
+## Every row of @var{T} contains four indices into the n by 3 matrix @var{X} 
+## of the vertices of a tetrahedron. 
+## Every row in @var{X} represents one point in 3D space. 
+##
+## If the vector @var{C} is supplied it must contain indices into the current 
+## colormap. Called without @var{C} it is set to 1:m, where m is the number of
+## tetrahedrons, the indices are scaled to map to the full range of the colormap. 
+## If more tetrahedrons than entries in the colormap are given the entries of
+## @var{C} are cyclic repeated.
+## 
+## When called with one output argument @var{H} it returns a vector of patch 
+##  handles,each representing one tetrahedron in the order given by @var{T}. 
+## One use case for @var{H} is to turn the respective patch 'Visible' property 
+## 'on' or 'off'.
+##
+## Calling tetramesh(...,'param','value','param','value'...) passes all
+## option/value pairs directly as additional arguments to the patch function for
+## every tetrahedron.
+##
+## The command
+##
+##@example
+## @group
+## demo tetramesh
+## @end group
+## @end example
+##
+## @noindent
+## will show some examples how to use it.
+#### @seealso{patch}
+## @end deftypefn
+
+## Author: Martin Helm <martin@mhelm.de>
+
+function [h] = tetramesh (varargin)
+
+  [reg, prop] = parseparams (varargin);
+
+  if (length (reg) < 2 || length (reg) > 3)
+    print_usage ()
+  endif
+
+  T = reg{1};
+  X = reg{2};
+
+  if (! ismatrix (T) || size (T, 2) != 4)
+    error ("tetramesh: T must be a n by 4 matrix")
+  endif
+  if (! ismatrix (X) || size (X, 2) != 3)
+    error ("tetramesh: X must be a n by 3 matrix")
+  endif
+
+  size_T = size (T, 1);
+  colmap = colormap ();
+  
+  # do we need to enable gnuplot workaround?
+  shrink = strcmp (graphics_toolkit (), "gnuplot");
+
+  if (length (reg) < 3)
+    size_colmap = size (colmap, 1);
+    C = mod ((1:size_T)' - 1, size_colmap) + 1;
+    if (size_T < size_colmap && size_T > 1) 
+      # expand to the available range of colors
+      C = floor ((C - 1) * (size_colmap - 1) / (size_T - 1)) + 1;
+    endif
+  else
+    C = reg{3};
+    if (! isvector (C) || size_T != length (C))
+      error ("tetramesh: C must be a vector of the same length as T")
+    endif
+  endif
+
+  h = zeros (1, size_T);
+  if (shrink)
+    # tiny reduction of the tetrahedron size to help gnuplot by
+    # avoiding identical faces with different colors
+    for ii = 1:size_T
+      [th, p] = __shrink__ ([1 2 3 4], X(T(ii, :), :), 1 - 1e-7);
+      h(ii) = patch ("Faces", th, "Vertices", p, "FaceColor", ...
+                     colmap(C(ii), :), prop{:});
+    endfor
+  else
+    for ii = 1:size_T
+      th = [1 2 3; 2 3 4; 3 4 1; 4 1 2];
+      h(ii) = patch ("Faces", th, "Vertices", X(T(ii, :), :), "FaceColor", ...
+                     colmap(C(ii), :), prop{:});
+    endfor
+  endif
+
+  if (nargout == 0) #return nothing
+    clear h;
+  endif
+endfunction
+
+## shrink the tetrahedron relative to its center of gravity
+function [tri, p] = __shrink__ (T, X, sf)
+  midpoint = repmat (sum (X(T, :), 1) / 4, 12, 1);
+  p = [X([1 2 3], :); X([2 3 4], :); X([3 4 1], :); X([4 1 2], :)];
+  p = sf * (p - midpoint) + midpoint;
+  tri = reshape (1:12, 3, 4)';
+endfunction
+
+%!demo
+%! d = [-1 1];
+%! [x,y,z] = meshgrid (d, d, d);
+%! x = [x(:); 0];
+%! y = [y(:); 0];
+%! z = [z(:); 0];
+%! tetra = delaunay3 (x, y, z);
+%! X = [x(:) y(:) z(:)];
+%! clf ()
+%! colormap (jet (64))
+%! h = tetramesh (tetra, X);
+%! for ii=1:2:length(h);
+%!   set(h(ii), "Visible", "off");
+%! endfor
+%! axis equal
+%! view (30, 20)
+%! title ("Using jet (64), every other tetrahedron invisible")
+
+%!demo
+%! d = [-1 1];
+%! [x,y,z] = meshgrid (d, d, d);
+%! x = [x(:); 0];
+%! y = [y(:); 0];
+%! z = [z(:); 0];
+%! tetra = delaunay3 (x, y, z);
+%! X = [x(:) y(:) z(:)];
+%! clf ()
+%! colormap (gray (256));
+%! tetramesh (tetra, X, 21:20:241, "EdgeColor", "w")
+%! axis equal
+%! view (30, 20)
+%! title ("Using gray (256) and white edges")