X-Git-Url: https://git.creatis.insa-lyon.fr/pubgit/?p=CreaPhase.git;a=blobdiff_plain;f=octave_packages%2Fm%2Fplot%2Fsurfnorm.m;fp=octave_packages%2Fm%2Fplot%2Fsurfnorm.m;h=c06f3312a7f6a67b688dcf130c260583ce25ac95;hp=0000000000000000000000000000000000000000;hb=1c0469ada9531828709108a4882a751d2816994a;hpb=63de9f36673d49121015e3695f2c336ea92bc278

diff --git a/octave_packages/m/plot/surfnorm.m b/octave_packages/m/plot/surfnorm.m
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+## Copyright (C) 2007-2012 David Bateman
+##
+## 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} {} surfnorm (@var{x}, @var{y}, @var{z})
+## @deftypefnx {Function File} {} surfnorm (@var{z})
+## @deftypefnx {Function File} {[@var{nx}, @var{ny}, @var{nz}] =} surfnorm (@dots{})
+## @deftypefnx {Function File} {} surfnorm (@var{h}, @dots{})
+## Find the vectors normal to a meshgridded surface.  The meshed gridded
+## surface is defined by @var{x}, @var{y}, and @var{z}.  If @var{x} and
+## @var{y} are not defined, then it is assumed that they are given by
+##
+## @example
+## @group
+## [@var{x}, @var{y}] = meshgrid (1:size (@var{z}, 1),
+##                    1:size (@var{z}, 2));
+## @end group
+## @end example
+##
+## If no return arguments are requested, a surface plot with the normal
+## vectors to the surface is plotted.  Otherwise the components of the normal
+## vectors at the mesh gridded points are returned in @var{nx}, @var{ny},
+## and @var{nz}.
+##
+## The normal vectors are calculated by taking the cross product of the
+## diagonals of each of the quadrilaterals in the meshgrid to find the
+## normal vectors of the centers of these quadrilaterals.  The four nearest
+## normal vectors to the meshgrid points are then averaged to obtain the
+## normal to the surface at the meshgridded points.
+##
+## An example of the use of @code{surfnorm} is
+##
+## @example
+## surfnorm (peaks (25));
+## @end example
+## @seealso{surf, quiver3}
+## @end deftypefn
+
+function [Nx, Ny, Nz] = surfnorm (varargin)
+
+  [h, varargin, nargin] = __plt_get_axis_arg__ ((nargout != 0), "surfnorm",
+                                                varargin{:});
+
+  if (nargin != 1 && nargin != 3)
+    print_usage ();
+  endif
+
+  if (nargin == 1)
+    z = varargin{1};
+    [x, y] = meshgrid (1:size(z,1), 1:size(z,2));
+    ioff = 2;
+  else
+    x = varargin{1};
+    y = varargin{2};
+    z = varargin{3};
+    ioff = 4;
+  endif
+
+  if (!ismatrix (z) || isvector (z) || isscalar (z))
+    error ("surfnorm: Z argument must be a matrix");
+  endif
+  if (! size_equal (x, y, z))
+    error ("surfnorm: X, Y, and Z must have the same dimensions");
+  endif
+
+  ## Make life easier, and avoid having to do the extrapolation later, do
+  ## a simpler linear extrapolation here. This is approximative, and works
+  ## badly for closed surfaces like spheres.
+  xx = [2 .* x(:,1) - x(:,2), x, 2 .* x(:,end) - x(:,end-1)];
+  xx = [2 .* xx(1,:) - xx(2,:); xx; 2 .* xx(end,:) - xx(end-1,:)];
+  yy = [2 .* y(:,1) - y(:,2), y, 2 .* y(:,end) - y(:,end-1)];
+  yy = [2 .* yy(1,:) - yy(2,:); yy; 2 .* yy(end,:) - yy(end-1,:)];
+  zz = [2 .* z(:,1) - z(:,2), z, 2 .* z(:,end) - z(:,end-1)];
+  zz = [2 .* zz(1,:) - zz(2,:); zz; 2 .* zz(end,:) - zz(end-1,:)];
+
+  u.x = xx(1:end-1,1:end-1) - xx(2:end,2:end);
+  u.y = yy(1:end-1,1:end-1) - yy(2:end,2:end);
+  u.z = zz(1:end-1,1:end-1) - zz(2:end,2:end);
+  v.x = xx(1:end-1,2:end) - xx(2:end,1:end-1);
+  v.y = yy(1:end-1,2:end) - yy(2:end,1:end-1);
+  v.z = zz(1:end-1,2:end) - zz(2:end,1:end-1);
+
+  c = cross ([u.x(:), u.y(:), u.z(:)], [v.x(:), v.y(:), v.z(:)]);
+  w.x = reshape (c(:,1), size(u.x));
+  w.y = reshape (c(:,2), size(u.y));
+  w.z = reshape (c(:,3), size(u.z));
+
+  ## Create normal vectors as mesh vectices from normals at mesh centers
+  nx = (w.x(1:end-1,1:end-1) + w.x(1:end-1,2:end) +
+        w.x(2:end,1:end-1) + w.x(2:end,2:end)) ./ 4;
+  ny = (w.y(1:end-1,1:end-1) + w.y(1:end-1,2:end) +
+        w.y(2:end,1:end-1) + w.y(2:end,2:end)) ./ 4;
+  nz = (w.z(1:end-1,1:end-1) + w.z(1:end-1,2:end) +
+        w.z(2:end,1:end-1) + w.z(2:end,2:end)) ./ 4;
+
+  ## Normalize the normal vectors
+  len = sqrt (nx.^2 + ny.^2 + nz.^2);
+  nx = nx ./ len;
+  ny = ny ./ len;
+  nz = nz ./ len;
+
+  if (nargout == 0)
+    oldh = gca ();
+    unwind_protect
+      axes (h);
+      newplot ();
+      surf (x, y, z, varargin{ioff:end});
+      old_hold_state = get (h, "nextplot");
+      unwind_protect
+        set (h, "nextplot", "add");
+        plot3 ([x(:)'; x(:).' + nx(:).' ; NaN(size(x(:).'))](:),
+               [y(:)'; y(:).' + ny(:).' ; NaN(size(y(:).'))](:),
+               [z(:)'; z(:).' + nz(:).' ; NaN(size(z(:).'))](:),
+               varargin{ioff:end});
+      unwind_protect_cleanup
+        set (h, "nextplot", old_hold_state);
+      end_unwind_protect
+    unwind_protect_cleanup
+      axes (oldh);
+    end_unwind_protect
+  else
+    Nx = nx;
+    Ny = ny;
+    Nz = nz;
+  endif
+
+endfunction
+
+%!demo
+%! clf
+%! colormap (jet (64))
+%! [x, y, z] = peaks(10);
+%! surfnorm (x, y, z);
+
+%!demo
+%! clf
+%! surfnorm (peaks(10));
+
+%!demo
+%! clf
+%! surfnorm (peaks(32));
+%! shading interp