combine two meshes

Former-commit-id: cd907682c78b88c727ddb26e58104362a8f43531

include/igl/combine.cpp

@@ -0,0 +1,57 @@
+// This file is part of libigl, a simple c++ geometry processing library.
+// 
+// Copyright (C) 2016 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 "combine.h"
+#include <cassert>
+template <
+  typename DerivedVV, 
+  typename DerivedFF, 
+  typename DerivedV, 
+  typename DerivedF>
+IGL_INLINE void igl::combine(
+  const std::vector<DerivedVV> & VV,
+  const std::vector<DerivedFF> & FF,
+  Eigen::PlainObjectBase<DerivedV> & V,
+  Eigen::PlainObjectBase<DerivedF> & F)
+{
+  assert(VV.size() == FF.size() && 
+    "Lists of verex lists and face lists should be same size");
+  // Dimension of vertex positions
+  const int dim = VV.size() > 0 ? VV[0].cols() : 0;
+  // Simplex/element size
+  const int ss = FF.size() > 0 ? FF[0].cols() : 0;
+  int n = 0;
+  int m = 0;
+  for(int i = 0;i<VV.size();i++)
+  {
+    const auto & Vi = VV[i];
+    const auto & Fi = FF[i];
+    n+=Vi.rows();
+    assert(dim == Vi.cols() && "All vertex lists should have same #columns");
+    m+=Fi.rows();
+    assert(ss == Fi.cols() && "All face lists should have same #columns");
+  }
+  V.resize(n,dim);
+  F.resize(m,ss);
+  {
+    int kv = 0;
+    int kf = 0;
+    for(int i = 0;i<VV.size();i++)
+    {
+      const auto & Vi = VV[i];
+      const int ni = Vi.rows();
+      const auto & Fi = FF[i];
+      const int mi = Fi.rows();
+      F.block(kf,0,mi,ss) = Fi.array()+kv;
+      kf+=mi;
+      V.block(kv,0,ni,dim) = Vi;
+      kv+=ni;
+    }
+    assert(kv == V.rows());
+    assert(kf == F.rows());
+  }
+}

include/igl/combine.h

@@ -0,0 +1,48 @@
+// This file is part of libigl, a simple c++ geometry processing library.
+// 
+// Copyright (C) 2016 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_COMBINE_H
+#define IGL_COMBINE_H
+
+#include "igl_inline.h"
+#include <Eigen/Core>
+#include <vector>
+
+namespace igl
+{
+  // Combine k meshes into a single >=k connected component mesh with a single
+  // vertex list and face list. Similar to Maya's Combine operation.
+  //
+  // Inputs:
+  //   VV  k-long list of lists of mesh vertex positions
+  //   FF  k-long list of lists of mesh face indices so that FF[i] indexes
+  //     VV[i]
+  // Outputs:
+  //   V   VV[0].rows()+...+VV[k-1].rows() by VV[0].cols() list of mesh
+  //     vertex positions
+  //   F   FF[0].rows()+...+FF[k-1].rows() by FF[0].cols() list of mesh faces
+  //     indices into V
+  // Example:
+  //   // Suppose you have mesh A (VA,FA) and mesh B (VB,FB)
+  //   igl::combine<Eigen::MatrixXd,Eigen::MatrixXi>({VA,VB},{FA,FB},V,F);
+  //
+  template <
+    typename DerivedVV, 
+    typename DerivedFF, 
+    typename DerivedV, 
+    typename DerivedF>
+  IGL_INLINE void combine(
+    const std::vector<DerivedVV> & VV,
+    const std::vector<DerivedFF> & FF,
+    Eigen::PlainObjectBase<DerivedV> & V,
+    Eigen::PlainObjectBase<DerivedF> & F);
+}
+
+#ifndef IGL_STATIC_LIBRARY
+#  include "combine.cpp"
+#endif
+#endif