From 8ce1dc352cb5639a01a5ebaf566af1cfb03ab40e Mon Sep 17 00:00:00 2001
From: Daniel Zint <daniel.zint@mail.de>
Date: Fri, 27 Jun 2025 14:15:00 +0200
Subject: [PATCH] Test for comparing different non-manifold splitting methods.

---
 tests/test_manifold.cpp | 91 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)

diff --git a/tests/test_manifold.cpp b/tests/test_manifold.cpp
index 4beb4cf665..641de269ce 100644
--- a/tests/test_manifold.cpp
+++ b/tests/test_manifold.cpp
@@ -1,4 +1,5 @@
 #include <igl/read_triangle_mesh.h>
+#include <igl/split_nonmanifold.h>
 #include <wmtk/TetMesh.h>
 #include <catch2/catch_test_macros.hpp>
 
@@ -45,3 +46,93 @@ TEST_CASE("manifold-separate-test-37989", "[test_util]")
     Eigen::VectorXi VI;
     REQUIRE(igl::is_vertex_manifold(F, VI));
 }
+
+TEST_CASE("compare_lagrange_igl", "[test_util][.]")
+{
+    wmtk::manifold_internal::Vertices V;
+    wmtk::manifold_internal::Facets F;
+
+    // SECTION("simple")
+    //{
+    //     F.resize(2, 3);
+    //     F.row(0) << 0, 1, 2;
+    //    F.row(1) << 1, 0, 3; // same orientation
+    //
+    //    V.resize(4, 3);
+    //    V.setZero();
+    //}
+    SECTION("twisted")
+    {
+        F.resize(2, 3);
+        F.row(0) << 0, 1, 2;
+        F.row(1) << 0, 1, 3; // different orientation
+
+        V.resize(4, 3);
+        V.setZero();
+    }
+    SECTION("large")
+    {
+        std::string filename = WMTK_DATA_DIR "/37989_sf.obj";
+        igl::read_triangle_mesh(filename, V, F);
+        // REQUIRE_FALSE(igl::is_edge_manifold(F));
+        // std::vector<size_t> modified_vertices;
+        // wmtk::manifold_internal::resolve_nonmanifoldness(V, F, modified_vertices);
+        // REQUIRE(modified_vertices.size() > 0);
+        // REQUIRE(igl::is_edge_manifold(F));
+        // Eigen::VectorXi VI;
+        // REQUIRE(igl::is_vertex_manifold(F, VI));
+    }
+
+    {
+        Eigen::VectorXi SVI;
+        wmtk::manifold_internal::Facets SF;
+        igl::split_nonmanifold(F, SF, SVI);
+        // std::cout << "IGL:\n" << SF << std::endl;
+
+        wmtk::manifold_internal::Vertices V_new;
+        V_new.resize(SVI.size(), V.cols());
+        std::map<uint64_t, uint64_t> used_vids; // map old vertex ID to first new ID
+        std::set<int> modified_vertices;
+        for (int i = 0; i < SVI.size(); ++i) {
+            auto old_vid = SVI[i];
+
+            V_new.row(i) = V.row(old_vid);
+            if (used_vids.count(old_vid) > 0) {
+                // vertex was duplicated
+                modified_vertices.insert(used_vids[old_vid]);
+                modified_vertices.insert(i);
+            } else {
+                used_vids[old_vid] = i; // store first occurance
+            }
+        }
+
+        // F = SF;
+
+        // std::cout << SVI.transpose() << std::endl;
+        // std::cout << "IGL MOD: ";
+        // for (const auto v : modified_vertices) {
+        //     std::cout << v << " ";
+        // }
+        // std::cout << std::endl;
+        std::cout << "IGL " << modified_vertices.size() << std::endl;
+
+        CHECK(igl::is_edge_manifold(SF));
+        Eigen::VectorXi VI;
+        CHECK(igl::is_vertex_manifold(SF, VI));
+    }
+    {
+        std::vector<size_t> modified_vertices;
+        wmtk::manifold_internal::resolve_nonmanifoldness(V, F, modified_vertices);
+        // std::cout << "LAG:\n" << F << std::endl;
+        // std::cout << "LAG MOD: ";
+        // for (const auto v : modified_vertices) {
+        //     std::cout << v << " ";
+        // }
+        // std::cout << std::endl;
+        std::cout << "LAG " << modified_vertices.size() << std::endl;
+
+        CHECK(igl::is_edge_manifold(F));
+        Eigen::VectorXi VI;
+        CHECK(igl::is_vertex_manifold(F, VI));
+    }
+}