convex hull

Former-commit-id: e8a0218abcf1ce8325d4daf9d6ba37db954d84b1

include/igl/copyleft/cgal/convex_hull.cpp

@@ -0,0 +1,72 @@
+// This file is part of libigl, a simple c++ geometry processing library.
+// 
+// Copyright (C) 2017 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/.
+#include "convex_hull.h"
+#include "../../ismember.h"
+#include "polyhedron_to_mesh.h"
+#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
+#include <CGAL/Polyhedron_3.h>
+#include <CGAL/Surface_mesh.h>
+#include <CGAL/convex_hull_3.h>
+#include <vector>
+
+template <
+  typename DerivedV,
+  typename DerivedW,
+  typename DerivedG>
+IGL_INLINE void igl::copyleft::cgal::convex_hull(
+  const Eigen::MatrixBase<DerivedV> & V,
+  Eigen::PlainObjectBase<DerivedW> & W,
+  Eigen::PlainObjectBase<DerivedG> & G)
+{
+  typedef CGAL::Exact_predicates_inexact_constructions_kernel      K;
+  typedef K::Point_3                                              Point_3;
+  //typedef CGAL::Delaunay_triangulation_3<K>                       Delaunay;
+  //typedef Delaunay::Vertex_handle                                 Vertex_handle;
+  //typedef CGAL::Surface_mesh<Point_3>                             Surface_mesh;
+  typedef CGAL::Polyhedron_3<K>                             Polyhedron_3;
+  std::vector<Point_3> points(V.rows());
+  for(int i = 0;i<V.rows();i++)
+  {
+    points[i] = Point_3(V(i,0),V(i,1),V(i,2));
+  }
+  Polyhedron_3 poly;
+  CGAL::convex_hull_3(points.begin(),points.end(),poly);
+  assert(poly.is_pure_triangle() && "Assuming CGAL outputs a triangle mesh");
+  polyhedron_to_mesh(poly,W,G);
+}
+
+template <
+  typename DerivedV,
+  typename DerivedF>
+IGL_INLINE void igl::copyleft::cgal::convex_hull(
+  const Eigen::MatrixBase<DerivedV> & V,
+  Eigen::PlainObjectBase<DerivedF> & F)
+{
+  Eigen::Matrix<typename DerivedV::Scalar, Eigen::Dynamic, Eigen::Dynamic> W;
+  Eigen::Matrix<typename DerivedF::Scalar, Eigen::Dynamic, Eigen::Dynamic> G;
+  convex_hull(V,W,G);
+  // This is a lazy way to reindex into the original mesh
+  Eigen::Matrix<bool,Eigen::Dynamic,1> I;
+  Eigen::VectorXi J;
+  igl::ismember_rows(W,V,I,J);
+  assert(I.all() && "Should find all W in V");
+  F.resizeLike(G);
+  for(int f = 0;f<G.rows();f++)
+  {
+    for(int c = 0;c<3;c++)
+    {
+      F(f,c) = J(G(f,c));
+    }
+  }
+}
+
+#ifdef IGL_STATIC_LIBRARY
+// Explicit template instantiation
+// generated by autoexplicit.sh
+template void igl::copyleft::cgal::convex_hull<Eigen::Matrix<double, -1, 3, 0, -1, 3>, Eigen::Matrix<int, -1, -1, 0, -1, -1> >(Eigen::MatrixBase<Eigen::Matrix<double, -1, 3, 0, -1, 3> > const&, Eigen::PlainObjectBase<Eigen::Matrix<int, -1, -1, 0, -1, -1> >&);
+#endif

include/igl/copyleft/cgal/convex_hull.h

@@ -0,0 +1,56 @@
+// This file is part of libigl, a simple c++ geometry processing library.
+// 
+// Copyright (C) 2017 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_COPYLEFT_CGAL_CONVEX_HULL_H
+#define IGL_COPYLEFT_CGAL_CONVEX_HULL_H
+#include "../../igl_inline.h"
+#include <Eigen/Core>
+
+namespace igl
+{
+  namespace copyleft
+  {
+    namespace cgal
+    {
+      // Given a set of points (V), compute the convex hull as a triangle mesh (W,G)
+      // 
+      // Inputs:
+      //   V  #V by 3 list of input points
+      // Outputs:
+      //   W  #W by 3 list of convex hull points
+      //   G  #G by 3 list of triangle indices into W
+      template <
+        typename DerivedV,
+        typename DerivedW,
+        typename DerivedG>
+      IGL_INLINE void convex_hull(
+        const Eigen::MatrixBase<DerivedV> & V,
+        Eigen::PlainObjectBase<DerivedW> & W,
+        Eigen::PlainObjectBase<DerivedG> & G);
+      // Given a set of points (V), compute the convex hull as a triangle mesh (F)
+      // over input vertex set (V)
+      // 
+      // Inputs:
+      //   V  #V by 3 list of input points
+      // Outputs:
+      //   F  #F by 3 list of triangle indices into V
+      //
+      template <
+        typename DerivedV,
+        typename DerivedF>
+      IGL_INLINE void convex_hull(
+        const Eigen::MatrixBase<DerivedV> & V,
+        Eigen::PlainObjectBase<DerivedF> & F);
+    }
+  }
+}
+  
+#ifndef IGL_STATIC_LIBRARY
+#  include "convex_hull.cpp"
+#endif
+
+#endif