FIX:add "split mesh and save relationship" api

jira: none
Change-Id: Ib4c225b7fb75a27bd74f1a60b8842cbc4880e4f6

src/libslic3r/MeshSplitImpl.hpp

@@ -184,6 +184,81 @@ std::vector<indexed_triangle_set> its_split(const Its &its)
     return ret;
 }
 
+// Splits a mesh into multiple meshes when possible.
+template<class Its, class OutputIt, class OutputIt_ship>
+void its_split_and_keep_relationship(const Its &m, OutputIt out_it, OutputIt_ship out_ship)
+{
+    using namespace meshsplit_detail;
+
+    const indexed_triangle_set &its = ItsWithNeighborsIndex_<Its>::get_its(m);
+
+    struct VertexConv
+    {
+        size_t part_id = std::numeric_limits<size_t>::max();
+        size_t vertex_image;
+    };
+    std::vector<VertexConv> vidx_conv(its.vertices.size());
+
+    meshsplit_detail::NeighborVisitor visitor(its, meshsplit_detail::ItsWithNeighborsIndex_<Its>::get_index(m));
+
+    std::vector<size_t> facets;
+    for (size_t part_id = 0;; ++part_id) {
+        // Collect all faces of the next patch.
+        facets.clear();
+        visitor.visit([&facets](size_t idx) {
+            facets.emplace_back(idx);
+            return true;
+        });
+        if (facets.empty()) break;
+        std::sort(facets.begin(), facets.end());
+        // Create a new mesh for the part that was just split off.
+        indexed_triangle_set mesh;
+        mesh.indices.reserve(facets.size());
+        mesh.vertices.reserve(std::min(facets.size() * 3, its.vertices.size()));
+        std::unordered_map<int, int> relationship;
+        // Assign the facets to the new mesh.
+        for (size_t face_id : facets) {
+            const auto &face = its.indices[face_id];
+            Vec3i       new_face;
+            for (size_t v = 0; v < 3; ++v) {
+                auto vi = face(v);
+
+                if (vidx_conv[vi].part_id != part_id) {
+                    vidx_conv[vi] = {part_id, mesh.vertices.size()};
+                    mesh.vertices.emplace_back(its.vertices[size_t(vi)]);
+                }
+
+                new_face(v) = vidx_conv[vi].vertex_image;
+            }
+            relationship[mesh.indices.size()] = face_id;
+            mesh.indices.emplace_back(new_face);
+        }
+
+        *out_it   = std::move(mesh);
+        *out_ship = std::move(relationship);
+        ++out_it;
+    }
+}
+class MeshAndShip
+{
+public:
+    std::vector<indexed_triangle_set>         itses;
+    std::vector<std::unordered_map<int, int>> ships;
+};
+
+template<class Its>
+MeshAndShip its_split_and_save_relationship(const Its &its)
+{
+    auto ret      = reserve_vector<indexed_triangle_set>(3);
+    auto ret_ship = reserve_vector<std::unordered_map<int, int>>(3);
+
+    its_split_and_keep_relationship(its, std::back_inserter(ret), std::back_inserter(ret_ship));
+    MeshAndShip mesh_ship;
+    mesh_ship.itses = ret;
+    mesh_ship.ships = ret_ship;
+    return mesh_ship;
+}
+
 template<class Its>
 bool its_is_splittable(const Its &m)
 {

src/libslic3r/Model.cpp

@@ -3243,9 +3243,12 @@ std::string ModelVolume::type_to_string(const ModelVolumeType t)
 // This is useful to assign different materials to different volumes of an object.
 size_t ModelVolume::split(unsigned int max_extruders)
 {
-    std::vector<TriangleMesh> meshes = this->mesh().split();
+    std::vector<std::unordered_map<int, int>> ships;
+    std::vector<TriangleMesh>  meshes = this->mesh().split_and_save_relationship(ships);
     if (meshes.size() <= 1)
         return 1;
+    if (meshes.size() != ships.size())
+        return 1;
     // splited volume should not be text object
     size_t idx = 0;
     size_t ivolume = std::find(this->object->volumes.begin(), this->object->volumes.end(), this) - this->object->volumes.begin();
@@ -3279,17 +3282,23 @@ size_t ModelVolume::split(unsigned int max_extruders)
             this->exterior_facets.reset();
             this->supported_facets.reset();
             this->seam_facets.reset();
-            for (size_t i = 0; i < tris_split_strs.size(); i++) {
+            for (size_t i = 0; i < cur_face_count; i++) {
-                if (i < cur_face_count && tris_split_strs[i].size()>0) {
+                if (ships[idx].find(i) != ships[idx].end()) {
-                    mmu_segmentation_facets.set_triangle_from_string(i, tris_split_strs[i]);
+                    auto index = ships[idx][i];
+                    if (tris_split_strs[index].size() > 0) {
+                        mmu_segmentation_facets.set_triangle_from_string(i, tris_split_strs[index]);
+                    }
                 }
             }
         } else {
             auto new_mv =new ModelVolume(object, *this, std::move(mesh));
             this->object->volumes.insert(this->object->volumes.begin() + (++ivolume), new_mv);
-            for (size_t i = last_all_mesh_face_count; i < tris_split_strs.size(); i++) {
+            for (size_t i = 0; i < new_mv->mesh_ptr()->its.indices.size(); i++) {
-                if (i < last_all_mesh_face_count + cur_face_count && tris_split_strs[i].size() > 0) {
+                if (ships[idx].find(i) != ships[idx].end()) {
-                    new_mv->mmu_segmentation_facets.set_triangle_from_string(i - last_all_mesh_face_count, tris_split_strs[i]);
+                    auto index = ships[idx][i];
+                    if (tris_split_strs[index].size() > 0) {
+                        new_mv->mmu_segmentation_facets.set_triangle_from_string(i, tris_split_strs[index]);
+                    }
                 }
             }
         }

src/libslic3r/TriangleMesh.cpp

@@ -406,6 +406,29 @@ std::vector<TriangleMesh> TriangleMesh::split() const
     return out;
 }
 
+std::vector<TriangleMesh> TriangleMesh::split_and_save_relationship(std::vector<std::unordered_map<int, int>> &result) const {
+    auto   itss_and_ships = its_split_and_save_relationship<>(this->its);
+    std::vector<TriangleMesh>         out;
+    out.reserve(itss_and_ships.itses.size());
+    result.reserve(itss_and_ships.itses.size());
+    unsigned int index = 0;
+    for (indexed_triangle_set &m : itss_and_ships.itses) {
+        // The TriangleMesh constructor shall fill in the mesh statistics including volume.
+        TriangleMesh temp_triangle_mesh(std::move(m));
+        if (abs(temp_triangle_mesh.volume() < 0.01)) { // 0.01mm^3
+            index++;
+            continue;
+        }
+        if (temp_triangle_mesh.volume() < 0) { // Some source mesh parts may be incorrectly oriented. Correct them.
+            temp_triangle_mesh.flip_triangles();
+        }
+        out.emplace_back(temp_triangle_mesh);
+        result.emplace_back(itss_and_ships.ships[index]);
+        index++;
+    }
+    return out;
+}
+
 void TriangleMesh::merge(const TriangleMesh &mesh)
 {
     its_merge(this->its, mesh.its);

src/libslic3r/TriangleMesh.hpp

@@ -119,6 +119,7 @@ public:
     void align_to_origin();
     void rotate(double angle, Point* center);
     std::vector<TriangleMesh> split() const;
+    std::vector<TriangleMesh> split_and_save_relationship(std::vector<std::unordered_map<int, int>> &result) const;
     void merge(const TriangleMesh &mesh);
     ExPolygons horizontal_projection() const;
     // 2D convex hull of a 3D mesh projected into the Z=0 plane.