feat: implement export_halfpatch_obj function to generate OBJ and MTL files for half-patches

network_process/src/process.cpp

@@ -4,6 +4,63 @@
 #include <connect_by_topo.hpp>
 #include <post_topo.hpp>
 
+#include <fstream>
+
+
+void export_halfpatch_obj(
+    const stl_vector_mp<Eigen::Vector3d>& iso_pts,
+    const stl_vector_mp<polygon_face_t>& iso_faces,
+    const stl_vector_mp<stl_vector_mp<uint32_t>>& patches,
+    const std::string& filename)
+{
+    std::string mtl_filename = filename + ".mtl";
+    std::ofstream mtl(mtl_filename);
+    for (size_t half_patch = 0; half_patch < patches.size() * 2; ++half_patch) {
+        size_t patch_idx = half_patch / 2;
+        bool is_forward = (half_patch % 2 == 0);
+        mtl << "newmtl patch_" << patch_idx << (is_forward ? "_in" : "_out") << "\n";
+        // 随机或规律分配颜色
+        float r = float(patch_idx % 7) / 7.0f;
+        float g = is_forward ? 0.8f : 0.2f;
+        float b = 1.0f - r;
+        mtl << "Kd " << r << " " << g << " " << b << "\n";
+    }
+    mtl.close();
+
+    std::string obj_filename = filename + ".obj";
+    std::ofstream ofs(obj_filename);
+    if (!ofs) return;
+
+    ofs << "mtllib "<< mtl_filename << "\n";
+
+    // 输出所有顶点
+    for (const auto& v : iso_pts) {
+        ofs << "v " << v.x() << " " << v.y() << " " << v.z() << "\n";
+    }
+
+    // 遍历所有 half-patch
+    for (size_t half_patch = 0; half_patch < patches.size() * 2; ++half_patch) {
+        size_t patch_idx = half_patch / 2;
+        bool is_forward = (half_patch % 2 == 0);
+        ofs << "g halfpatch_" << half_patch << "\n";
+        ofs << "usemtl patch_" << patch_idx << (is_forward ? "_in" : "_out") << "\n";
+        for (auto face_idx : patches[patch_idx]) {
+            const auto& face = iso_faces[face_idx];
+            ofs << "f";
+            if (is_forward) {
+                for (auto vi : face.vertex_indices)
+                    ofs << " " << (vi + 1);
+            } else {
+                for (auto it = face.vertex_indices.rbegin(); it != face.vertex_indices.rend(); ++it)
+                    ofs << " " << (*it + 1);
+            }
+            ofs << "\n";
+        }
+    }
+    ofs.close();
+}
+
+
 ISNP_API void build_implicit_network_by_blobtree(const s_settings&               settings,
                                                  const baked_blobtree_t&         tree,
                                                  stl_vector_mp<Eigen::Vector3d>& output_vertices,
@@ -87,6 +144,7 @@ ISNP_API void build_implicit_network_by_blobtree(const s_settings&
             compute_patch_edges(iso_faces, edges_of_iso_face, iso_edges);
             compute_patches(edges_of_iso_face, iso_edges, iso_faces, patches, patch_of_face);
             compute_chains(iso_verts.size(), iso_edges, chains);
+            export_halfpatch_obj(iso_pts, iso_faces, patches, "halfpatch_before_connect");
         }
         stl_vector_mp<stl_vector_mp<uint32_t>> half_patch_adj_list(2 * patches.size());
         for (size_t i = 0; i < chains.size(); ++i)
@@ -161,6 +219,9 @@ ISNP_API void build_implicit_network_by_blobtree(const s_settings&
                                  output_polygon_faces,
                                  output_vertex_counts_of_face);
             filter_active_vertices(output_vertices, output_polygon_faces);
+            export_halfpatch_obj(iso_pts, iso_faces, patches, "halfpatch_final");
         }
     }
-}
+}
+
+