Merged branch 'dev_native' into lm_sla_supports_auto

Added igl library files

src/igl/edge_collapse_is_valid.cpp

@@ -0,0 +1,86 @@
+// 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/.
+#include "edge_collapse_is_valid.h"
+#include "collapse_edge.h"
+#include "circulation.h"
+#include "intersect.h"
+#include "unique.h"
+#include "list_to_matrix.h"
+#include <vector>
+
+IGL_INLINE bool igl::edge_collapse_is_valid(
+  const int e,
+  const Eigen::MatrixXi & F,
+  const Eigen::MatrixXi & E,
+  const Eigen::VectorXi & EMAP,
+  const Eigen::MatrixXi & EF,
+  const Eigen::MatrixXi & EI)
+{
+  using namespace Eigen;
+  using namespace std;
+  // For consistency with collapse_edge.cpp, let's determine edge flipness
+  // (though not needed to check validity)
+  const int eflip = E(e,0)>E(e,1);
+  // source and destination
+  const int s = eflip?E(e,1):E(e,0);
+  const int d = eflip?E(e,0):E(e,1);
+
+  if(s == IGL_COLLAPSE_EDGE_NULL && d==IGL_COLLAPSE_EDGE_NULL)
+  {
+    return false;
+  }
+  // check if edge collapse is valid: intersection of vertex neighbors of s and
+  // d should be exactly 2+(s,d) = 4
+  // http://stackoverflow.com/a/27049418/148668
+  {
+    // all vertex neighbors around edge, including the two vertices of the edge
+    const auto neighbors = [](
+      const int e,
+      const bool ccw,
+      const Eigen::MatrixXi & F,
+      const Eigen::MatrixXi & E,
+      const Eigen::VectorXi & EMAP,
+      const Eigen::MatrixXi & EF,
+      const Eigen::MatrixXi & EI) 
+    {
+      vector<int> N,uN;
+      vector<int> V2Fe = circulation(e, ccw,F,E,EMAP,EF,EI);
+      for(auto f : V2Fe)
+      {
+        N.push_back(F(f,0));
+        N.push_back(F(f,1));
+        N.push_back(F(f,2));
+      }
+      vector<size_t> _1,_2;
+      igl::unique(N,uN,_1,_2);
+      VectorXi uNm;
+      list_to_matrix(uN,uNm);
+      return uNm;
+    };
+    VectorXi Ns = neighbors(e, eflip,F,E,EMAP,EF,EI);
+    VectorXi Nd = neighbors(e,!eflip,F,E,EMAP,EF,EI);
+    VectorXi Nint = igl::intersect(Ns,Nd);
+    if(Nint.size() != 4)
+    {
+      return false;
+    }
+    if(Ns.size() == 4 && Nd.size() == 4)
+    {
+      VectorXi NsNd(8);
+      NsNd<<Ns,Nd;
+      VectorXi Nun,_1,_2;
+      igl::unique(NsNd,Nun,_1,_2);
+      // single tet, don't collapse
+      if(Nun.size() == 4)
+      {
+        return false;
+      }
+    }
+  }
+  return true;
+}