libigl_Martin/include/igl/copyleft/cgal/point_areas.h

// This file is part of libigl, a simple c++ geometry processing library.
//
// Copyright (C) 2018 Gavin Barill <gavinpcb@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_POINT_AREAS_H
#define IGL_POINT_AREAS_H
#include "../../igl_inline.h"
#include <Eigen/Core>
namespace igl
{
  namespace copyleft
  {
    namespace cgal
    {
    // Given a 3D set of points P, each with a list of k-nearest-neighbours,
    // estimate the geodesic voronoi area associated with each point.
    //
    // The k nearest neighbours may be known from running igl::knn_octree on
    // the output data from igl::octree. We reccomend using a k value
    // between 15 and 20 inclusive for accurate area estimation.
    //
    // N is used filter the neighbours, to ensure area estimation only occurs
    // using neighbors that are on the same side of the surface (ie for thin
    // sheets), as well as to solve the orientation ambiguity of the tangent
    // plane normal.
    //
    // Note: This function *should* be implemented by pre-filtering I, rather
    // than filtering in this function using N. In this case, the function
    // would only take P and I as input.
    //
    // Inputs:
    //   P  #P by 3 list of point locations
    //   I  #P by k list of k-nearest-neighbor indices into P
    //   N  #P by 3 list of point normals
    // Outputs:
    //   A  #P list of estimated areas
    template <typename DerivedP, typename DerivedI, typename DerivedN,
      typename DerivedA>
    IGL_INLINE void point_areas(
                                        const Eigen::MatrixBase<DerivedP>& P,
                                        const Eigen::MatrixBase<DerivedI>& I,
                                        const Eigen::MatrixBase<DerivedN>& N,
                                        Eigen::PlainObjectBase<DerivedA> & A);
      
    // This version can be used to output the tangent plane normal at each
    // point. Since we area already fitting a plane to each point's neighbour
    // set, the tangent plane normals come "for free"
    //
    // Inputs:
    //   P  #P by 3 list of point locations
    //   I  #P by k list of k-nearest-neighbor indices into P
    //   N  #P by 3 list of point normals
    // Outputs:
    //   A  #P list of estimated areas
    //   T  #P by 3 list of tangent plane normals for each point
    template <typename DerivedP, typename DerivedI, typename DerivedN,
    typename DerivedA, typename DerivedT>
    IGL_INLINE void point_areas(
                                const Eigen::MatrixBase<DerivedP>& P,
                                const Eigen::MatrixBase<DerivedI>& I,
                                const Eigen::MatrixBase<DerivedN>& N,
                                Eigen::PlainObjectBase<DerivedA> & A,
                                Eigen::PlainObjectBase<DerivedT> & T);
      
    }
  }
}

#ifndef IGL_STATIC_LIBRARY
#  include "point_areas.cpp"
#endif

#endif