split windows header-only tutorial actions (#2238)

* split windows header-only tutorial actions * double quote issue? * split 7 into 8 and 9
2023-08-19 11:06:48 -04:00
parent 83922780e1
commit 7765697eb6
16 changed files with 46 additions and 17 deletions
@@ -0,0 +1,144 @@
+#include <igl/read_triangle_mesh.h>
+#include <igl/parula.h>
+#include <igl/remove_unreferenced.h>
+#include <igl/opengl/glfw/Viewer.h>
+#include <igl/per_face_normals.h>
+#include <igl/orient_halfedges.h>
+#include <igl/cr_vector_laplacian.h>
+#include <igl/cr_vector_mass.h>
+#include <igl/edge_midpoints.h>
+#include <igl/edge_vectors.h>
+#include <igl/average_from_edges_onto_vertices.h>
+#include <igl/PI.h>
+
+#include <Eigen/Core>
+#include <Eigen/SparseCholesky>
+#include <Eigen/Geometry>
+
+#include <iostream>
+#include <set>
+#include <limits>
+#include <stdlib.h>
+
+
+int main(int argc, char * argv[])
+{
+  typedef Eigen::SparseMatrix<double> SparseMat;
+
+  //Constants used for smoothing
+  const double howMuchToSmoothBy = 1e-1;
+  const int howManySmoothingInterations = 50;
+
+  //Read our mesh
+  Eigen::MatrixXd V;
+  Eigen::MatrixXi F;
+  if(!igl::read_triangle_mesh
+     (argc>1?argv[1]: TUTORIAL_SHARED_PATH "/elephant.obj",V,F)) {
+    std::cout << "Failed to load mesh." << std::endl;
+  }
+
+  //Orient edges for plotting
+  Eigen::MatrixXi E, oE;
+  igl::orient_halfedges(F, E, oE);
+
+  //Compute edge midpoints & edge vectors
+  Eigen::MatrixXd edgeMps, parVec, perpVec;
+  igl::edge_midpoints(V, F, E, oE, edgeMps);
+  igl::edge_vectors(V, F, E, oE, parVec, perpVec);
+
+  //Constructing a function to add noise to
+  const auto zraw_function = [] (const Eigen::Vector3d& x) {
+    return Eigen::Vector3d(0.2*x(1) + cos(2*x(1)+0.2),
+                           0.5*x(0) + 0.15,
+                           0.3*cos(0.2+igl::PI*x(2)));
+  };
+
+  Eigen::VectorXd zraw(2*edgeMps.rows());
+  for(int i=0; i<edgeMps.rows(); ++i) {
+    const Eigen::Vector3d f = zraw_function(edgeMps.row(i));
+    zraw(i) = f.dot(parVec.row(i));
+    zraw(i+edgeMps.rows()) = f.dot(perpVec.row(i));
+  }
+
+  //Add noise
+  srand(71);
+  const double l = 15;
+  Eigen::VectorXd znoisy = zraw + l*Eigen::VectorXd::Random(zraw.size());
+
+  //Denoise function using the vector Dirichlet energy
+  Eigen::VectorXd zsmoothed = znoisy;
+  for(int i=0; i<howManySmoothingInterations; ++i) {
+    //Compute Laplacian and mass matrix
+    SparseMat L, M;
+    igl::cr_vector_mass(V, F, E, oE, M);
+    igl::cr_vector_laplacian(V, F, E, oE, L);
+
+    //Implicit step
+    Eigen::SimplicialLDLT<SparseMat> rhsSolver(M + howMuchToSmoothBy*L);
+    zsmoothed = rhsSolver.solve(M*zsmoothed);
+  }
+
+  //Convert vector fields for plotting
+  const auto cr_result_to_vecs_and_colors = [&]
+  (const Eigen::VectorXd& z, Eigen::MatrixXd& vecs, Eigen::MatrixXd& colors) {
+    vecs.resize(edgeMps.rows(), 3);
+    for(int i=0; i<edgeMps.rows(); ++i) {
+      vecs.row(i) = z(i)*parVec.row(i)
+      + z(i+edgeMps.rows())*perpVec.row(i);
+    }
+    igl::average_from_edges_onto_vertices
+    (F, E, oE, vecs.rowwise().norm().eval(), colors);
+  };
+  Eigen::MatrixXd noisyvecs, noisycolors, smoothedvecs, smoothedcolors,
+  rawvecs, rawcolors;
+  cr_result_to_vecs_and_colors(znoisy, noisyvecs, noisycolors);
+  cr_result_to_vecs_and_colors(zsmoothed, smoothedvecs, smoothedcolors);
+  cr_result_to_vecs_and_colors(zraw, rawvecs, rawcolors);
+
+
+  //Viewer that shows noisy and denoised functions
+  igl::opengl::glfw::Viewer viewer;
+  viewer.data().set_mesh(V,F);
+  viewer.data().show_lines = false;
+  viewer.callback_key_down =
+  [&](igl::opengl::glfw::Viewer & viewer, unsigned char key, int mod)->bool
+  {
+    const Eigen::MatrixXd *vecs, *colors;
+    switch(key) {
+      case '1':
+        vecs = &rawvecs;
+        colors = &rawcolors;
+        break;
+      case '2':
+        vecs = &noisyvecs;
+        colors = &noisycolors;
+        break;
+      case '3':
+        vecs = &smoothedvecs;
+        colors = &smoothedcolors;
+        break;
+      default:
+        return false;
+    }
+    viewer.data().set_data(*colors);
+    viewer.data().clear_edges();
+    const double s = 0.08; //How much to scale vectors during plotting
+    viewer.data().add_edges(edgeMps, edgeMps + s*(*vecs),
+                            Eigen::RowVector3d(0.1, 0.1, 0.1));
+    return true;
+  };
+  std::cout << R"(Usage:
+1  Show raw function
+2  Show noisy function
+3  Show smoothed function
+
+)";
+  Eigen::MatrixXd CM;
+  igl::parula(Eigen::VectorXd::LinSpaced
+              (500,znoisy.minCoeff(), znoisy.maxCoeff()).eval(), true, CM);
+  viewer.data().set_colormap(CM);
+  viewer.callback_key_down(viewer, '1', 0);
+  viewer.launch();
+
+  return 0;
+}