add binding for marching_cubes_e2v

src/marching_cubes_e2v.cpp

@@ -0,0 +1,109 @@
+// This file is part of libigl, a simple c++ geometry processing library.
+//
+// Copyright (C) 2023 Thomas
+//
+// 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 <common.h>
+#include <npe.h>
+#include <typedefs.h>
+#include <pybind11/stl.h>
+
+#include <igl/marching_cubes.h>
+
+const char* ds_marching_cubes_e2v = R"igl_Qu8mg5v7(
+
+marching_cubes performs marching cubes reconstruction on a grid defined by values, and 
+points, and generates a mesh defined by vertices and faces
+
+Parameters
+----------
+S   nx*ny*nz list of values at each grid corner i.e. S(x + y*xres + z*xres*yres) for corner (x,y,z)
+GV  nx*ny*nz by 3 array of corresponding grid corner vertex locations
+        points, ordered in x,y,z order:
+        points[index] = the point at (x,y,z) where :
+            x = (index % (xres -1),
+            y = (index / (xres-1)) %(yres-1),
+            z = index / (xres -1) / (yres -1) ).
+            where x,y,z index x, y, z dimensions
+            i.e. index = x + y*xres + z*xres*yres
+nx  resolutions of the grid in x dimension
+ny  resolutions of the grid in y dimension
+nz  resolutions of the grid in z dimension
+isovalue  the isovalue of the surface to reconstruct
+
+
+Returns
+-------
+V  #V by 3 list of mesh vertex positions
+F  #F by 3 list of mesh triangle indices into rows of V
+
+See also
+--------
+
+
+Notes
+-----
+None
+
+Examples
+--------
+>> import numpy as np
+>> K = np.linspace( -1.0, 1.0, 64)
+>> pts = np.array([[x,y,z] for x in K for y in K for z in K])
+>> S = signed_distance(pts, v, f)
+>> v, f = marching_cubes(S, pts, nx, ny, nz, 0.0)
+
+)igl_Qu8mg5v7";
+
+npe_function(marching_cubes_e2v)
+npe_doc(ds_marching_cubes_e2v)
+npe_arg(s, dense_float, dense_double)
+npe_arg(gv, dense_float, dense_double)
+npe_arg(nx, int)
+npe_arg(ny, int)
+npe_arg(nz, int)
+npe_default_arg(isovalue, double, 0.0)
+
+npe_begin_code()
+    // input checks
+    assert_rows_match(s, gv, "S", "GV");
+    assert_cols_equals(s, 1, "S");
+    assert_cols_equals(gv, 3, "GV");
+
+    // vertices and faces of marched iso surface
+    Eigen::MatrixXd SV;
+    Eigen::MatrixXi SF;
+    std::unordered_map<std::int64_t,int> E2V; 
+
+    Eigen::MatrixXd s_copy = s.template cast<double>();
+    Eigen::MatrixXd gv_copy = gv.template cast<double>();
+
+    igl::marching_cubes(s_copy, gv_copy, nx, ny, nz, isovalue, SV, SF, E2V);
+
+    // serialize E2V to a |E2V| x 3 matrix 
+    size_t num_elements = E2V.size();
+    Eigen::MatrixXd E2VMatrix(num_elements, 3);
+    const auto key2ij = [](const std::int64_t & key, std::int32_t & i, std::int32_t & j)
+    {
+        i = key & 0xFFFFFFFF;
+        j = key >> 32;
+    };
+    size_t row = 0;
+    for (const auto& pair : E2V) {
+        // Extract the value (which is an Eigen::Vector3d)
+        std::int64_t key = pair.first;
+        std::int32_t i,j;
+        key2ij(key,i,j);
+        int val = pair.second;
+
+        E2VMatrix.row(row)<<i,j,val; 
+        ++row;
+    }
+
+    EigenDenseLike<npe_Matrix_gv> svRowMajor = SV.template cast<typename npe_Matrix_gv::Scalar>();
+    EigenDenseLike<EigenDenseInt> sfRowMajor = SF.template cast<typename EigenDenseInt::Scalar>();
+
+    return std::make_tuple(npe::move(svRowMajor), npe::move(sfRowMajor), npe::move(E2VMatrix));
+npe_end_code()