Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / vrml-1.0.13 / vrml_ellipsoid.m

diff --git a/octave_packages/vrml-1.0.13/vrml_ellipsoid.m b/octave_packages/vrml-1.0.13/vrml_ellipsoid.m
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+## Copyright (C) 2002 Etienne Grossmann <etienne@egdn.net>
+##
+## This program 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.
+##
+## This program 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
+## this program; if not, see <http://www.gnu.org/licenses/>.
+
+##       v = vrml_ellipsoid (moment, col) - Ellipsoid 
+##
+## moment : 3x3 : Define elipsoid by x'*moment*x = 1
+##  or      3   :  use diag(moment)
+##  or      1   :  use diag(moment([1,1,1]))   default : eye(3)
+##
+## col    : 3   : Color                        default : [0.3 0.4 0.9]
+##
+
+function v = vrml_ellipsoid(moment, col)
+
+
+if nargin<2  || isempty (col) || isnan (col), col = [0.3 0.4 0.9];
+else
+  error ("vrml_ellipsoid : col has size %d x %d. This won't do\n",size(col));
+  ## keyboard
+end
+col = col' ;
+
+
+if nargin<1 || isempty (moment),  moment = eye(3),
+elseif all (size (moment) == 3), # Do nothing
+elseif prod( size (moment)) == 3, moment = diag (moment);
+elseif length (moment) == 1,      moment = moment*eye(3);
+else 
+  error ("vrml_ellipsoid : moment has size %d x %d. This won't do\n",size(moment));
+  ## keyboard
+end
+
+[u,d,v] = svd (moment);
+d = diag(d);
+d(find(d)) = 1 ./ nze (d) ;
+
+[r,a] = rotparams (u');
+
+v = sprintf (["Transform {\n",\
+              "  translation  0 0 0\n",\
+             "  rotation     %8.3g %8.3g %8.3g %8.3g\n",\
+             "  scale        %8.3g %8.3g %8.3g\n",\
+              "  children [\n",\
+              "    Shape {\n",\
+              "      appearance  Appearance {\n",\
+              "        material Material {\n",\
+             "          diffuseColor  %8.3g %8.3g %8.3g\n",\
+             "          emissiveColor %8.3g %8.3g %8.3g\n",\
+             "        }\n",\
+              "      }\n",\
+              "      geometry Sphere {}\n",\
+              "    }\n",\
+              "  ]\n",\
+              "}\n",\
+              ],\
+            r,a,\
+            d,\
+            col,\
+            col/20);
+
+endfunction
+## Example
+## d0 = sort (1+2*rand(1,3));
+## d0 = 1:3;
+## rv = randn (1,3); 
+## uu = rotv (rv);
+## dd = diag (1./d0);
+## mm = uu*dd*uu';
+## vrml_browse ([vrml_frame ([0,0,0],uu',"col",eye(3),"scale",2*d0), vrml_ellipsoid(mm)]);