Export negative parts (#7024)

Porting from Prusa exporting negative parts.

Before:

![image](https://github.com/user-attachments/assets/a5e041ce-7f0f-44e5-95ea-0a8b11252cc4)

After:

![image](https://github.com/user-attachments/assets/f0a6f6bb-13c7-4a6e-afb3-7631e2f4f634)

src/libslic3r/CSGMesh/CSGMesh.hpp

@@ -82,6 +82,40 @@ struct CSGPart {
  {}
 };
 
+//Prusa
+// Check if there are only positive parts (Union) within the collection.
+template<class Cont> bool is_all_positive(const Cont &csgmesh)
+{
+ bool is_all_pos =
+ std::all_of(csgmesh.begin(),
+ csgmesh.end(),
+ [](auto &part) {
+ return csg::get_operation(part) == csg::CSGType::Union;
+ });
+
+ return is_all_pos;
+}
+
+//Prusa
+// Merge all the positive parts of the collection into a single triangle mesh without performing
+// any booleans.
+template<class Cont>
+indexed_triangle_set csgmesh_merge_positive_parts(const Cont &csgmesh)
+{
+ indexed_triangle_set m;
+ for (auto &csgpart : csgmesh) {
+ auto op = csg::get_operation(csgpart);
+ const indexed_triangle_set * pmesh = csg::get_mesh(csgpart);
+ if (pmesh && op == csg::CSGType::Union) {
+ indexed_triangle_set mcpy = *pmesh;
+ its_transform(mcpy, csg::get_transform(csgpart), true);
+ its_merge(m, mcpy);
+ }
+ }
+
+ return m;
+}
+
 }} // namespace Slic3r::csg
 
 #endif // CSGMESH_HPP

src/libslic3r/CSGMesh/PerformCSGMeshBooleans.hpp

@@ -257,7 +257,7 @@ void perform_csgmesh_booleans_mcut(MeshBoolean::mcut::McutMeshPtr& mcutm,
 
 
 template<class It, class Visitor>
-std::tuple<BooleanFailReason,std::string> check_csgmesh_booleans(const Range<It> &csgrange, Visitor &&vfn)
+std::tuple<BooleanFailReason,std::string, It> check_csgmesh_booleans(const Range<It> &csgrange, Visitor &&vfn)
 {
  using namespace detail_cgal;
  BooleanFailReason fail_reason = BooleanFailReason::OK;
@@ -304,23 +304,23 @@ std::tuple<BooleanFailReason,std::string> check_csgmesh_booleans(const Range<It>
  };
  execution::for_each(ex_tbb, size_t(0), csgrange.size(), check_part);
 
- //It ret = csgrange.end();
- //for (size_t i = 0; i < csgrange.size(); ++i) {
- // if (!cgalmeshes[i]) {
- // auto it = csgrange.begin();
- // std::advance(it, i);
- // vfn(it);
+ It ret = csgrange.end();
+ for (size_t i = 0; i < csgrange.size(); ++i) {
+ if (!cgalmeshes[i]) {
+ auto it = csgrange.begin();
+ std::advance(it, i);
+ vfn(it);
 
- // if (ret == csgrange.end())
- // ret = it;
- // }
- //}
+ if (ret == csgrange.end())
+ ret = it;
+ }
+ }
 
- return { fail_reason,fail_part_name };
+ return { fail_reason,fail_part_name, ret};
 }
 
 template<class It>
-std::tuple<BooleanFailReason, std::string> check_csgmesh_booleans(const Range<It> &csgrange, bool use_mcut=false)
+std::tuple<BooleanFailReason, std::string, It> check_csgmesh_booleans(const Range<It> &csgrange, bool use_mcut=false)
 {
  if(!use_mcut)
  return check_csgmesh_booleans(csgrange, [](auto &) {});
@@ -354,7 +354,7 @@ std::tuple<BooleanFailReason, std::string> check_csgmesh_booleans(const Range<It
  McutMeshes[i] = std::move(m);
  };
  execution::for_each(ex_tbb, size_t(0), csgrange.size(), check_part);
- return { fail_reason,fail_part_name };
+ return { fail_reason,fail_part_name, csgrange.end() };
  }
 }
 

src/slic3r/GUI/Plater.cpp

@@ -11686,14 +11686,37 @@ void Plater::export_stl(bool extended, bool selection_only, bool multi_stls)
  }
 
  // Following lambda generates a combined mesh for export with normals pointing outwards.
- auto mesh_to_export_fff_no_boolean = [](const ModelObject &mo, int instance_id) {
+ auto mesh_to_export_fff_no_boolean = [this](const ModelObject &mo, int instance_id) {
  TriangleMesh mesh;
- for (const ModelVolume *v : mo.volumes)
- if (v->is_model_part()) {
- TriangleMesh vol_mesh(v->mesh());
- vol_mesh.transform(v->get_matrix(), true);
- mesh.merge(vol_mesh);
- }
+
+ //Prusa export negative parts
+ std::vector<csg::CSGPart> csgmesh;
+ csgmesh.reserve(2 * mo.volumes.size());
+ csg::model_to_csgmesh(mo, Transform3d::Identity(), std::back_inserter(csgmesh),
+ csg::mpartsPositive | csg::mpartsNegative | csg::mpartsDoSplits);
+
+ auto csgrange = range(csgmesh);
+ if (csg::is_all_positive(csgrange)) {
+ mesh = TriangleMesh{csg::csgmesh_merge_positive_parts(csgrange)};
+ } else if (std::get<2>(csg::check_csgmesh_booleans(csgrange)) == csgrange.end()) {
+ try {
+ auto cgalm = csg::perform_csgmesh_booleans(csgrange);
+ mesh = MeshBoolean::cgal::cgal_to_triangle_mesh(*cgalm);
+ } catch (...) {}
+ }
+
+ if (mesh.empty()) {
+ get_notification_manager()->push_plater_error_notification(
+ _u8L("Unable to perform boolean operation on model meshes. "
+ "Only positive parts will be exported."));
+
+ for (const ModelVolume* v : mo.volumes)
+ if (v->is_model_part()) {
+ TriangleMesh vol_mesh(v->mesh());
+ vol_mesh.transform(v->get_matrix(), true);
+ mesh.merge(vol_mesh);
+ }
+ }
  if (instance_id == -1) {
  TriangleMesh vols_mesh(mesh);
  mesh = TriangleMesh();