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// This file is part of libigl, a simple c++ geometry processing library.
//
// Copyright (C) 2015 Alec Jacobson <alecjacobson@gmail.com>
//
// This Source Code Form is subject to the terms of the Mozilla Public License
// v. 2.0. If a copy of the MPL was not distributed with this file, You can
// obtain one at http://mozilla.org/MPL/2.0/.
#ifndef IGL_NORMAL_DERIVATIVE_H
#define IGL_NORMAL_DERIVATIVE_H
#include "igl_inline.h"
#include <Eigen/Core>
#include <Eigen/Sparse>
namespace igl
{
/// Computes the directional derivative **normal** to
/// **all** (half-)edges of a triangle mesh (not just boundary edges). These
/// are integrated along the edge: they're the per-face constant gradient dot
/// the rotated edge vector (unit rotated edge vector for direction then
/// magnitude for integration).
///
/// @param[in] V #V by dim list of mesh vertex positions
/// @param[in] F #F by 3|4 list of triangle|tetrahedron indices into V
/// @param[out] DD #F*3|4 by #V sparse matrix representing operator to compute
/// directional derivative with respect to each facet of each element.
template <
typename DerivedV,
typename DerivedEle,
typename Scalar>
IGL_INLINE void normal_derivative(
const Eigen::MatrixBase<DerivedV> & V,
const Eigen::MatrixBase<DerivedEle> & Ele,
Eigen::SparseMatrix<Scalar>& DD);
}
#ifndef IGL_STATIC_LIBRARY
# include "normal_derivative.cpp"
#endif
#endif