exploded view of tetrahedral meshes

tutorial/719_ExplodedView/main.cpp

@@ -0,0 +1,99 @@
+// This file is part of libigl, a simple c++ geometry processing library.
+// 
+// Copyright (C) 2020 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 <igl/opengl/glfw/Viewer.h>
+#include <igl/readMESH.h>
+#include <igl/barycenter.h>
+#include <igl/volume.h>
+#include <igl/exploded_view.h>
+#include <igl/slice.h>
+#include <igl/colormap.h>
+
+
+int main(int argc, char *argv[])
+{
+
+  Eigen::MatrixXd V;
+  Eigen::MatrixXi T,F;
+  igl::readMESH(argc>1?argv[1]: TUTORIAL_SHARED_PATH "/octopus-low.mesh",V,T,F);
+  // Some per-tet data
+  Eigen::VectorXd D;
+  {
+    Eigen::MatrixXd BC;
+    igl::barycenter(V,T,BC);
+    Eigen::VectorXd vol;
+    igl::volume(V,T,vol);
+    const Eigen::RowVectorXd c = vol.transpose()*BC/vol.array().sum();
+    D = (BC.rowwise()-c).rowwise().norm();
+  }
+
+  // Plot the mesh
+  igl::opengl::glfw::Viewer viewer;
+
+  double t = 1;
+  double s = 1;
+  const auto update = [&]()
+  {
+    Eigen::MatrixXd EV;
+    Eigen::MatrixXi EF;
+    Eigen::VectorXi I,J;
+    igl::exploded_view(V,T,s,t,EV,EF,I,J);
+    Eigen::VectorXd DJ;
+    igl::slice(D,J,1,DJ);
+    static bool first = true;
+    if(first)
+    {
+      viewer.data().clear();
+      viewer.data().set_mesh(EV,EF);
+      first = false;
+    }else
+    {
+      viewer.data().set_vertices(EV);
+    }
+    viewer.data().set_face_based(true);
+    Eigen::MatrixXd C;
+    igl::colormap(igl::COLOR_MAP_TYPE_VIRIDIS,DJ,true,C);
+    viewer.data().set_colors(C);
+  };
+  int mod = 0;
+  float prev_y;
+  viewer.callback_mouse_move = [&](igl::opengl::glfw::Viewer &, int x, int y)->bool
+  {
+    if((mod & IGL_MOD_SHIFT)||(mod & IGL_MOD_ALT))
+    {
+      if(mod & IGL_MOD_SHIFT)
+      {
+        t = std::min(std::max(t+0.001*(y-prev_y),1.),2.);
+      }
+      if(mod & IGL_MOD_ALT)
+      {
+        s = std::min(std::max(s+0.001*(y-prev_y),0.),1.);
+      }
+      prev_y = y;
+      update();
+      return true;
+    }
+    return false;
+  };
+  // get modifier
+  viewer.callback_key_down = 
+    [&](igl::opengl::glfw::Viewer &, unsigned char key, int _mod)->bool
+  {
+    prev_y = viewer.current_mouse_y;
+    mod = _mod;
+    return false;
+  };
+  viewer.callback_key_up = 
+    [&](igl::opengl::glfw::Viewer &, unsigned char key, int _mod)->bool
+  {
+    mod = _mod;
+    return false;
+  };
+  update();
+  viewer.launch();
+}