Tetrahedral adjacenct functions (#835)

* Add tet_tet_adjacency

* added parallelization of the preprocessing

* Add tet_tet_adjacency

* added parallelization of the preprocessing

* Add tet_tet_adjacency

* added parallelization of the preprocessing

* Add tet_tet_adjacency

* added parallelization of the preprocessing

* Add tet_tet_adjacency

* added parallelization of the preprocessing

* Add tet_tet_adjacency

* added parallelization of the preprocessing

* Add tet_tet_adjacency

* Add tet_tet_adjacency

* added parallelization of the preprocessing

* added parallelization of the preprocessing

* fixed rebasing stuff

* Use template for index type


Former-commit-id: ab3f20c83e284b0082023f56226e38cacdbb1048

include/igl/tet_tet_adjacency.cpp

@@ -0,0 +1,68 @@
+// This file is part of libigl, a simple c++ geometry processing library.
+//
+// Copyright (C) 2018 Oded Stein <oded.stein@columbia.edu>
+//
+// 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 "tet_tet_adjacency.h"
+
+#include "parallel_for.h"
+
+#include <array>
+#include <vector>
+
+template <typename DerivedT, typename DerivedTT, typename DerivedTTi>
+IGL_INLINE void
+igl::tet_tet_adjacency(
+                       const Eigen::MatrixBase<DerivedT>& T,
+                       Eigen::PlainObjectBase<DerivedTT>& TT,
+                       Eigen::PlainObjectBase<DerivedTTi>& TTi)
+{
+  assert(T.cols()==4 && "Tets have four vertices.");
+  
+  //Preprocess
+  using Array = std::array<typename DerivedT::Scalar, 5>;
+  std::vector<Array> TTT(4*T.rows());
+  const auto loop_f = [&](const int t) {
+    TTT[4*t] = {T(t,0),T(t,1),T(t,2),t,0};
+    TTT[4*t+1] = {T(t,0),T(t,1),T(t,3),t,1};
+    TTT[4*t+2] = {T(t,1),T(t,2),T(t,3),t,2};
+    TTT[4*t+3] = {T(t,2),T(t,0),T(t,3),t,3};
+    for(int i=0; i<4; ++i)
+      std::sort(TTT[4*t+i].begin(), TTT[4*t+i].begin()+3);
+  };
+  
+  //for(int t=0; t<T.rows(); ++t)
+  //    loop_f(t);
+  igl::parallel_for(T.rows(), loop_f);
+  
+  std::sort(TTT.begin(),TTT.end());
+  
+  //Compute TT and TTi
+  TT.setConstant(T.rows(), T.cols(), -1);
+  TTi.setConstant(T.rows(), T.cols(), -1);
+  for(int i=1; i<TTT.size(); ++i) {
+    const Array& r1 = TTT[i-1];
+    const Array& r2 = TTT[i];
+    if((r1[0]==r2[0]) && (r1[1]==r2[1]) && (r1[2]==r2[2])) {
+      TT(r1[3],r1[4]) = r2[3];
+      TT(r2[3],r2[4]) = r1[3];
+      TTi(r1[3],r1[4]) = r2[4];
+      TTi(r2[3],r2[4]) = r1[4];
+    }
+  }
+}
+
+
+template <typename DerivedT, typename DerivedTT>
+IGL_INLINE void
+igl::tet_tet_adjacency(
+                       const Eigen::MatrixBase<DerivedT>& T,
+                       Eigen::PlainObjectBase<DerivedTT>& TT)
+{
+  DerivedTT TTi;
+  tet_tet_adjacency(T, TT, TTi);
+}

include/igl/tet_tet_adjacency.h

@@ -0,0 +1,51 @@
+// This file is part of libigl, a simple c++ geometry processing library.
+//
+// Copyright (C) 2018 Oded Stein <oded.stein@columbia.edu>
+//
+// 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_TET_TET_ADJACENCY_H
+#define IGL_TET_TET_ADJACENCY_H
+
+#include <Eigen/Core>
+
+#include <igl/igl_inline.h>
+
+namespace igl
+{
+  
+  // Constructs the tet_tet adjacency matrix for a given tet mesh with tets T
+  //
+  // Inputs:
+  //   T  #T by 4 list of tets
+  // Outputs:
+  //   TT   #T by #4 adjacency matrix, the element i,j is the id of the tet
+  //        adjacent to the j face of tet i
+  //   TTi  #T by #4 adjacency matrix, the element i,j is the id of face of
+  //        the tet TT(i,j) that is adjacent to tet i
+  //
+  // NOTE: the first face of a tet is [0,1,2], the second [0,1,3], the third
+  //       [1,2,3], and the fourth [2,0,3].
+  
+  template <typename DerivedT, typename DerivedTT, typename DerivedTTi>
+  IGL_INLINE void tet_tet_adjacency(
+                                    const Eigen::MatrixBase<DerivedT>& T,
+                                    Eigen::PlainObjectBase<DerivedTT>& TT,
+                                    Eigen::PlainObjectBase<DerivedTTi>& TTi);
+  
+  
+  template <typename DerivedT, typename DerivedTT>
+  IGL_INLINE void tet_tet_adjacency(
+                                    const Eigen::MatrixBase<DerivedT>& T,
+                                    Eigen::PlainObjectBase<DerivedTT>& TT);
+    
+}
+
+#ifndef IGL_STATIC_LIBRARY
+#  include "tet_tet_adjacency.cpp"
+#endif
+
+
+#endif