1 files changed, 46 insertions, 0 deletions
diff --git a/xs/src/igl/euler_characteristic.cpp b/xs/src/igl/euler_characteristic.cpp
new file mode 100644
index 000000000..ab7eba22b
--- /dev/null
+++ b/xs/src/igl/euler_characteristic.cpp
@@ -0,0 +1,46 @@
+// This file is part of libigl, a simple c++ geometry processing library.
+//
+// Copyright (C) 2016 Michael Rabinovich <michaelrabinovich27@gmail.com@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 "euler_characteristic.h"
+
+#include "edge_topology.h"
+#include "edges.h"
+
+template <typename Scalar, typename Index>
+IGL_INLINE int igl::euler_characteristic(
+  const Eigen::PlainObjectBase<Scalar> & V,
+  const Eigen::PlainObjectBase<Index> & F)
+{
+
+  int euler_v = V.rows();
+  Eigen::MatrixXi EV, FE, EF;
+  igl::edge_topology(V, F, EV, FE, EF);
+  int euler_e = EV.rows();
+  int euler_f = F.rows();
+
+  int euler_char = euler_v - euler_e + euler_f;
+  return euler_char;
+
+}
+
+template <typename DerivedF>
+IGL_INLINE int igl::euler_characteristic(
+  const Eigen::MatrixBase<DerivedF> & F)
+{
+  const int nf = F.rows();
+  const int nv = F.maxCoeff()+1;
+  Eigen::Matrix<typename DerivedF::Scalar,Eigen::Dynamic,2> E;
+  edges(F,E);
+  const int ne = E.rows();
+  return nv - ne + nf;
+}
+
+#ifdef IGL_STATIC_LIBRARY
+// Explicit template instantiation
+template int igl::euler_characteristic<Eigen::Matrix<double, -1, -1, 0, -1, -1>, Eigen::Matrix<int, -1, -1, 0, -1, -1> >(Eigen::PlainObjectBase<Eigen::Matrix<double, -1, -1, 0, -1, -1> > const&, Eigen::PlainObjectBase<Eigen::Matrix<int, -1, -1, 0, -1, -1> > const&);
+template int igl::euler_characteristic<Eigen::Matrix<int, -1, -1, 0, -1, -1> >(Eigen::MatrixBase<Eigen::Matrix<int, -1, -1, 0, -1, -1> > const&);
+#endif