Fixed some issues with front end / back end synchronization.

src/libslic3r/Model.cpp

@@ -254,6 +254,7 @@ void Model::clear_materials()
 
 ModelMaterial* Model::add_material(t_model_material_id material_id)
 {
+    assert(! material_id.empty());
     ModelMaterial* material = this->get_material(material_id);
     if (material == nullptr)
         material = this->materials[material_id] = new ModelMaterial(this);
@@ -262,6 +263,7 @@ ModelMaterial* Model::add_material(t_model_material_id material_id)
 
 ModelMaterial* Model::add_material(t_model_material_id material_id, const ModelMaterial &other)
 {
+    assert(! material_id.empty());
     // delete existing material if any
     ModelMaterial* material = this->get_material(material_id);
     delete material;
@@ -1134,7 +1136,8 @@ void ModelVolume::set_material_id(t_model_material_id material_id)
 {
     m_material_id = material_id;
     // ensure m_material_id references an existing material
-    this->object->get_model()->add_material(material_id);
+    if (! material_id.empty())
+        this->object->get_model()->add_material(material_id);
 }
 
 ModelMaterial* ModelVolume::material() const
@@ -1145,15 +1148,8 @@ ModelMaterial* ModelVolume::material() const
 void ModelVolume::set_material(t_model_material_id material_id, const ModelMaterial &material)
 {
     m_material_id = material_id;
-    this->object->get_model()->add_material(material_id, material);
-}
-
-ModelMaterial* ModelVolume::assign_unique_material()
-{
-    Model* model = this->get_object()->get_model();
-    // as material-id "0" is reserved by the AMF spec we start from 1
-    m_material_id = 1 + model->materials.size();  // watchout for implicit cast
-    return model->add_material(m_material_id);
+    if (! material_id.empty())
+        this->object->get_model()->add_material(material_id, material);
 }
 
 void ModelVolume::calculate_convex_hull()

src/libslic3r/Model.hpp

@@ -22,7 +22,6 @@ class ModelInstance;
 class ModelMaterial;
 class ModelObject;
 class ModelVolume;
-class PresetBundle;
 class Print;
 
 typedef std::string t_model_material_id;
@@ -323,8 +322,6 @@ public:
     void                rotate(double angle, const Vec3d& axis);
     void                mirror(Axis axis);
 
-    ModelMaterial*      assign_unique_material();
-    
     void                calculate_convex_hull();
     const TriangleMesh& get_convex_hull() const;
 
@@ -391,14 +388,15 @@ private:
         mesh(std::move(mesh)), m_convex_hull(std::move(convex_hull)), m_type(MODEL_PART), object(object) {}
 
 #if ENABLE_MODELVOLUME_TRANSFORM
+    // Copying an existing volume, therefore this volume will get a copy of the ID assigned.
     ModelVolume(ModelObject *object, const ModelVolume &other) :
         ModelBase(other), // copy the ID
         name(other.name), mesh(other.mesh), m_convex_hull(other.m_convex_hull), config(other.config), m_type(other.m_type), object(object), m_transformation(other.m_transformation)
     {
         this->set_material_id(other.material_id());
     }
+    // Providing a new mesh, therefore this volume will get a new unique ID assigned.
     ModelVolume(ModelObject *object, const ModelVolume &other, const TriangleMesh &&mesh) :
-        ModelBase(other), // copy the ID
         name(other.name), mesh(std::move(mesh)), config(other.config), m_type(other.m_type), object(object), m_transformation(other.m_transformation)
     {
         this->set_material_id(other.material_id());
@@ -406,12 +404,15 @@ private:
             calculate_convex_hull();
     }
 #else
+    // Copying an existing volume, therefore this volume will get a copy of the ID assigned.
     ModelVolume(ModelObject *object, const ModelVolume &other) :
+        ModelBase(other), // copy the ID
         name(other.name), mesh(other.mesh), m_convex_hull(other.m_convex_hull), config(other.config), m_type(other.m_type), object(object)
     {
 		if (! other.material_id().empty())
 			this->set_material_id(other.material_id());
     }
+    // Providing a new mesh, therefore this volume will get a new unique ID assigned.
     ModelVolume(ModelObject *object, const ModelVolume &other, TriangleMesh &&mesh) :
         name(other.name), mesh(std::move(mesh)), config(other.config), m_type(other.m_type), object(object)
     {

src/libslic3r/PrintObject.cpp

@@ -633,7 +633,7 @@ void PrintObject::detect_surfaces_type()
     // should be visible.
     bool interface_shells = m_config.interface_shells.value;
 
-    for (int idx_region = 0; idx_region < m_print->m_regions.size(); ++ idx_region) {
+    for (int idx_region = 0; idx_region < this->region_volumes.size(); ++ idx_region) {
         BOOST_LOG_TRIVIAL(debug) << "Detecting solid surfaces for region " << idx_region << " in parallel - start";
 #ifdef SLIC3R_DEBUG_SLICE_PROCESSING
         for (Layer *layer : m_layers)

xs/xsp/Model.xsp

@@ -286,8 +286,6 @@ ModelMaterial::attributes()
         %code%{ THIS->set_type(ModelVolume::SUPPORT_BLOCKER); %};
 
     size_t split(unsigned int max_extruders);
-    
-    ModelMaterial* assign_unique_material();
 };