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diff --git a/source/blender/freestyle/intern/geometry/normal_cycle.h b/source/blender/freestyle/intern/geometry/normal_cycle.h
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+/*
+ *  OGF/Graphite: Geometry and Graphics Programming Library + Utilities
+ *  Copyright (C) 2000 Bruno Levy
+ *
+ *  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 2 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, write to the Free Software
+ *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ *  If you modify this software, you should include a notice giving the
+ *  name of the person performing the modification, the date of modification,
+ *  and the reason for such modification.
+ *
+ *  Contact: Bruno Levy
+ *
+ *     levy@loria.fr
+ *
+ *     ISA Project
+ *     LORIA, INRIA Lorraine, 
+ *     Campus Scientifique, BP 239
+ *     54506 VANDOEUVRE LES NANCY CEDEX 
+ *     FRANCE
+ *
+ *  Note that the GNU General Public License does not permit incorporating
+ *  the Software into proprietary programs. 
+ */
+
+#ifndef __MESH_TOOLS_MATH_NORMAL_CYCLE__
+#define __MESH_TOOLS_MATH_NORMAL_CYCLE__
+
+# include "../system/FreestyleConfig.h"
+# include "Geom.h"
+using namespace Geometry;
+ 
+namespace OGF {
+
+template <class T> inline void ogf_swap(T& x, T& y) {
+        T z = x ;
+        x = y ;
+        y = z ;
+    }
+
+//_________________________________________________________
+
+    /**
+     * NormalCycle evaluates the curvature tensor in function
+     * of a set of dihedral angles and associated vectors.
+     * Reference:
+     *    Restricted Delaunay Triangulation and Normal Cycle,
+     *    D. Cohen-Steiner and J.M. Morvan,
+     *    SOCG 2003
+     */
+    class LIB_GEOMETRY_EXPORT NormalCycle {
+    public:
+        NormalCycle() ;
+        void begin() ;
+        void end() ;
+        /**
+         * Note: the specified edge vector needs to be pre-clipped
+         * by the neighborhood.
+         */
+        void accumulate_dihedral_angle(
+            const Vec3r& edge, real angle, real neigh_area = 1.0
+        ) ;
+        const Vec3r& eigen_vector(int i) const { return axis_[i_[i]] ; }
+        real eigen_value(int i) const   { return eigen_value_[i_[i]] ;  } 
+
+        const Vec3r& N() const    { return eigen_vector(2) ; }
+        const Vec3r& Kmax() const { return eigen_vector(1) ; }
+        const Vec3r& Kmin() const { return eigen_vector(0) ; }
+
+        real n() const    { return eigen_value(2) ; }
+        real kmax() const { return eigen_value(1) ; }
+        real kmin() const { return eigen_value(0) ; }
+
+    private:
+        real center_[3] ;
+        Vec3r axis_[3] ;
+        real eigen_value_[3] ;
+        real M_[6] ;
+        int i_[3] ;
+    } ;
+    
+    inline void NormalCycle::accumulate_dihedral_angle(
+        const Vec3r& edge, const double beta, double neigh_area
+    ) {
+        double s = beta * neigh_area / edge.norm();
+
+        M_[0] += s * edge.x() * edge.x() ;
+        M_[1] += s * edge.x() * edge.y() ;
+        M_[2] += s * edge.y() * edge.y() ;
+        M_[3] += s * edge.x() * edge.z() ;
+        M_[4] += s * edge.y() * edge.z() ;
+        M_[5] += s * edge.z() * edge.z() ;        
+    }
+    
+//_________________________________________________________
+
+}
+
+#endif