generalize grid to any dimension; 2d test

include/igl/grid.cpp

@@ -6,6 +6,7 @@
 // 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 "grid.h"
+#include <cassert>
 
 template <
   typename Derivedres,
@@ -16,23 +17,30 @@ IGL_INLINE void igl::grid(
 {
   using namespace Eigen;
   typedef typename DerivedGV::Scalar Scalar;
-  GV.resize(res(0)*res(1)*res(2),3);
-  for(int zi = 0;zi<res(2);zi++)
+  GV.resize(res.array().prod(),res.size());
+  const auto lerp = 
+    [&res](const Scalar di, const int d)->Scalar{return di/(Scalar)(res(d)-1);};
+  int gi = 0;
+  Derivedres sub;
+  sub.resizeLike(res);
+  sub.setConstant(0);
+  for(int gi = 0;gi<GV.rows();gi++)
   {
-    const auto lerp = 
-      [&](const Scalar di, const int d)->Scalar{return di/(Scalar)(res(d)-1);};
-    const Scalar z = lerp(zi,2);
-    for(int yi = 0;yi<res(1);yi++)
+    // omg, I'm implementing addition...
+    for(int c = 0;c<res.size()-1;c++)
     {
-      const Scalar y = lerp(yi,1);
-      for(int xi = 0;xi<res(0);xi++)
+      if(sub(c)>=res(c))
       {
-        const Scalar x = lerp(xi,0);
-        const int gi = xi+res(0)*(yi + res(1)*zi);
-        GV.row(gi) = 
-          Eigen::Matrix<Scalar,1,3>(x,y,z);
+        sub(c) = 0;
+        // roll over
+        sub(c+1)++;
       }
     }
+    for(int c = 0;c<res.size();c++)
+    {
+      GV(gi,c) = lerp(sub(c),c);
+    }
+    sub(0)++;
   }
 }
 
@@ -40,6 +48,8 @@ IGL_INLINE void igl::grid(
 #ifdef IGL_STATIC_LIBRARY
 // Explicit template instantiation
 // generated by autoexplicit.sh
+template void igl::grid<Eigen::Matrix<int, 2, 1, 0, 2, 1>, Eigen::Matrix<double, -1, -1, 0, -1, -1> >(Eigen::MatrixBase<Eigen::Matrix<int, 2, 1, 0, 2, 1> > const&, Eigen::PlainObjectBase<Eigen::Matrix<double, -1, -1, 0, -1, -1> >&);
+// generated by autoexplicit.sh
 template void igl::grid<Eigen::Matrix<int, 1, 3, 1, 1, 3>, Eigen::Matrix<float, -1, -1, 0, -1, -1> >(Eigen::MatrixBase<Eigen::Matrix<int, 1, 3, 1, 1, 3> > const&, Eigen::PlainObjectBase<Eigen::Matrix<float, -1, -1, 0, -1, -1> >&);
 // generated by autoexplicit.sh
 template void igl::grid<Eigen::Matrix<int, 3, 1, 0, 3, 1>, Eigen::Matrix<float, -1, 3, 0, -1, 3> >(Eigen::MatrixBase<Eigen::Matrix<int, 3, 1, 0, 3, 1> > const&, Eigen::PlainObjectBase<Eigen::Matrix<float, -1, 3, 0, -1, 3> >&);

include/igl/grid.h

@@ -1,6 +1,7 @@
 // This file is part of libigl, a simple c++ geometry processing library.
 // 
 // Copyright (C) 2016 Alec Jacobson <alecjacobson@gmail.com>
+// Copyright (C) 2018 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 
@@ -15,9 +16,9 @@ namespace igl
   // `igl::marching_cubes`
   //
   // Inputs:
-  //   res  3-long list of number of vertices along the x y and z dimensions
+  //   res  #res list of number of vertices along each dimension
   // Outputs:
-  //   GV  res(0)*res(1)*res(2) by 3 list of mesh vertex positions.
+  //   GV  res.array().prod() by #res list of mesh vertex positions.
   //   
   template <
     typename Derivedres,

tests/include/igl/grid.cpp

@@ -38,3 +38,22 @@ TEST(grid,3d)
       1,  1,  1).finished();
   test_common::assert_eq(GV,GVgt);
 }
+
+TEST(grid,2d)
+{
+  Eigen::Vector2i res(3,3);
+  Eigen::MatrixXd GV;
+  igl::grid(res,GV);
+  const Eigen::MatrixXd GVgt = 
+    (Eigen::MatrixXd(9,2)<<
+      0,  0,
+    0.5,  0,
+      1,  0,
+      0,0.5,
+    0.5,0.5,
+      1,0.5,
+      0,  1,
+    0.5,  1,
+      1,  1).finished();
+  test_common::assert_eq(GV,GVgt);
+}