From dd8c20757e3ff24b38b94f8261134ab9476e9baf Mon Sep 17 00:00:00 2001
From: augustin64 <me.git@augustin64.fr>
Date: Wed, 12 Mar 2025 12:15:05 +0100
Subject: [PATCH] Add Laplacian smoothing

---
 .../5-LaplacianSmoothing/c++/laplacian.cpp    | 33 +++++++++++++++++--
 1 file changed, 30 insertions(+), 3 deletions(-)

diff --git a/geometry-processing/5-LaplacianSmoothing/c++/laplacian.cpp b/geometry-processing/5-LaplacianSmoothing/c++/laplacian.cpp
index cdf83a0..cf0620b 100644
--- a/geometry-processing/5-LaplacianSmoothing/c++/laplacian.cpp
+++ b/geometry-processing/5-LaplacianSmoothing/c++/laplacian.cpp
@@ -1,3 +1,4 @@
+#include <CLI11.hpp>
 
 #include "geometrycentral/surface/manifold_surface_mesh.h"
 #include "geometrycentral/surface/meshio.h"
@@ -15,11 +16,31 @@ std::unique_ptr<ManifoldSurfaceMesh> mesh;
 std::unique_ptr<VertexPositionGeometry> geometry;
 
 int counter=0;
+float lambda = 0.5;
+
+Vector3 vertAverage(std::vector<Vector3> vertexPositions) {
+  assert(vertexPositions.size() > 0);
+
+  Vector3 out = {0, 0, 0};
+  for (auto i=0; i < vertexPositions.size(); i++) {
+    out = out + vertexPositions.at(i);
+  }
+  return out/vertexPositions.size();
+}
 
 void oneStep()
 {
-  for(size_t i = 0; i < mesh->nVertices(); ++i)
-    geometry->vertexPositions[i] = geometry->vertexPositions[i] + Vector3::constant(0.01*sin(i*counter/(2.0*M_PI)));
+  for(Vertex v : mesh->vertices()) {
+    std::vector<Vector3> adjVert;
+    adjVert.push_back(geometry->vertexPositions[v]);
+    for (Vertex v_adj : v.adjacentVertices()) {
+      adjVert.push_back(geometry->vertexPositions[v_adj]);
+    }
+    Vector3 avgPos = vertAverage(adjVert);
+    avgPos -= geometry->vertexPositions[v];
+
+    geometry->vertexPositions[v] += lambda*avgPos;
+  }
 }
 
 bool go=false;
@@ -41,12 +62,18 @@ void myCallback()
 
 
 int main(int argc, char **argv) {
+  CLI::App app{"laplacian"};
+  std::string inputObj;
+  app.add_option("-i,--input", inputObj, "Source Obj")->required()->check(CLI::ExistingFile);;
+  app.add_option("-l,--lambda", lambda, "Lambda (speed of transformation).");
+  CLI11_PARSE(app, argc, argv);
+  assert (lambda <= 1 && lambda > 0);
 
   // Initialize polyscope
   polyscope::init();
 
   // Load mesh
-  std::tie(mesh, geometry) = readManifoldSurfaceMesh(argv[1]);
+  std::tie(mesh, geometry) = readManifoldSurfaceMesh(inputObj);
 
   // Register the mesh with polyscope
   polyscope::registerSurfaceMesh("Input obj",