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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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+/*
+ * ***** BEGIN GPL LICENSE BLOCK *****
+ *
+ * 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * This Code is Copyright (C) 2010 Blender Foundation.
+ * All rights reserved.
+ *
+ * The Original Code is:
+ *   OGF/Graphite: Geometry and Graphics Programming Library + Utilities
+ *   Copyright (C) 2000 Bruno Levy
+ *   Contact: Bruno Levy
+ *      levy@loria.fr
+ *      ISA Project
+ *      LORIA, INRIA Lorraine, 
+ *      Campus Scientifique, BP 239
+ *      54506 VANDOEUVRE LES NANCY CEDEX 
+ *      FRANCE
+ *
+ * Contributor(s): none yet.
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ */
+
+#ifndef __MESH_TOOLS_MATH_NORMAL_CYCLE__
+#define __MESH_TOOLS_MATH_NORMAL_CYCLE__
+
+/** \file blender/freestyle/intern/geometry/normal_cycle.h
+ *  \ingroup freestyle
+ *  \author Bruno Levy
+ */
+
+#include "Geom.h"
+
+#include "../system/FreestyleConfig.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();
+}
+
+//_________________________________________________________
+
+}  // OGF namespace
+
+#endif  // __MESH_TOOLS_MATH_NORMAL_CYCLE__