diff --git a/lib/Slic3r/Model.pm b/lib/Slic3r/Model.pm
index efd331f1..d51d183e 100644
--- a/lib/Slic3r/Model.pm
+++ b/lib/Slic3r/Model.pm
@@ -20,18 +20,6 @@ sub read_from_file {
     return $model;
 }
 
-sub merge {
-    my $class = shift;
-    my @models = @_;
-    
-    my $new_model = ref($class)
-        ? $class
-        : $class->new;
-    
-    $new_model->add_object($_) for map @{$_->objects}, @models;
-    return $new_model;
-}
-
 sub add_object {
     my $self = shift;
     
diff --git a/xs/src/Model.cpp b/xs/src/Model.cpp
new file mode 100644
index 00000000..a4f5b9b2
--- /dev/null
+++ b/xs/src/Model.cpp
@@ -0,0 +1,84 @@
+#include "Model.hpp"
+
+namespace Slic3r {
+
+Model::~Model()
+{
+    for (t_model_materials::iterator it = this->materials.begin(); it != this->materials.end(); ++it)
+        delete it->second;
+    for (t_model_objects::iterator it = this->objects.begin(); it != this->objects.end(); ++it)
+        delete *it;
+}
+
+ModelObject*
+Model::add_object()
+{
+    ModelObject* retval = new ModelObject(this);
+    this->objects.push_back(retval);
+    return retval;
+}
+
+ModelObject*
+Model::add_object(const ModelObject &object)
+{
+    ModelObject* retval = new ModelObject(this, object);
+    this->objects.push_back(retval);
+    return retval;
+}
+
+void
+Model::delete_object(size_t obj_idx)
+{
+    this->objects.erase(this->objects.begin() + obj_idx);
+}
+
+void
+Model::delete_all_objects()
+{
+    this->objects.clear();
+}
+
+ModelMaterial*
+Model::set_material(t_model_material_id material_id, const t_model_material_attributes &attributes)
+{
+    ModelMaterial* material;
+    
+    // create material if it does not exist
+    t_model_materials::iterator itm = this->materials.find(material_id);
+    if (itm == this->materials.end()) {
+        material = new ModelMaterial(this);
+        this->materials[material_id] = material;
+    } else {
+        material = *itm;
+    }
+    
+    // apply attributes
+    for (t_model_material_attributes::const_iterator it = attributes.begin(); it != attributes.end(); ++it) {
+        material->attributes[it->first] = it->second;
+    }
+    
+    return material;
+}
+
+void
+Model::duplicate_objects_grid(unsigned int x, unsigned int y, coordf_t distance)
+{
+    if (this->objects.size() > 1) throw "Grid duplication is not supported with multiple objects";
+    
+    ModelObject* object = this->objects.front();
+    object->instances.clear();
+    
+    BoundingBoxf3 bb;
+    object->bounding_box(&bb);
+    Sizef3 size = bb.size();
+    
+    for (unsigned int x_copy = 1; x_copy <= x; ++x_copy) {
+        for (unsigned int y_copy = 1; y_copy <= y; ++y_copy) {
+            ModelInstance* instance = object->add_instance();
+            instance->offset.x = (size.x + distance) * (x_copy-1);
+            instance->offset.y = (size.y + distance) * (y_copy-1);
+        }
+    }
+}
+
+}
diff --git a/xs/src/Model.hpp b/xs/src/Model.hpp
index 6e16e8fa..cfd35adb 100644
--- a/xs/src/Model.hpp
+++ b/xs/src/Model.hpp
@@ -24,22 +24,26 @@ typedef std::map<t_model_material_attribute,std::string> t_model_material_attrib
 
 class Model
 {
-    public:
-    std::map<t_model_material_id,ModelMaterial*> materials;
-    std::vector<ModelObject*> objects;
+    typedef std::map<t_model_material_id,ModelMaterial*> t_model_materials;
+    typedef std::vector<ModelObject*> t_model_objects;
     
-    Model();
+    public:
+    t_model_materials materials;
+    t_model_objects objects;
+    
+    Model() {};
     ~Model();
+    ModelObject* add_object();
     ModelObject* add_object(const ModelObject &object);
     void delete_object(size_t obj_idx);
     void delete_all_objects();
-    void set_material(t_model_material_id material_id, const t_model_material_attributes &attributes);
-    void duplicate_objects_grid(coordf_t x, coordf_t y, coordf_t distance);
-    void duplicate_objects(size_t copies_num, coordf_t distance, const BoundingBox &bb);
-    void arrange_objects(coordf_t distance, const BoundingBox &bb);
-    void duplicate(size_t copies_num, coordf_t distance, const BoundingBox &bb);
+    ModelMaterial* set_material(t_model_material_id material_id, const t_model_material_attributes &attributes);
+    void duplicate_objects_grid(unsigned int x, unsigned int y, coordf_t distance);
+    void duplicate_objects(size_t copies_num, coordf_t distance, const BoundingBoxf &bb);
+    void arrange_objects(coordf_t distance, const BoundingBoxf &bb);
+    void duplicate(size_t copies_num, coordf_t distance, const BoundingBoxf &bb);
     bool has_objects_with_no_instances() const;
-    void bounding_box(BoundingBox* bb) const;
+    void bounding_box(BoundingBoxf3* bb) const;
     void align_to_origin();
     void center_instances_around_point(const Pointf &point);
     void translate(coordf_t x, coordf_t y, coordf_t z);
@@ -48,35 +52,44 @@ class Model
     std::string get_material_name(t_model_material_id material_id);
     
     private:
-    void _arrange(const std::vector<Size> &sizes, coordf_t distance, const BoundingBox &bb) const;
+    void _arrange(const std::vector<Size> &sizes, coordf_t distance, const BoundingBoxf &bb, Pointfs* positions) const;
 };
 
 class ModelMaterial
 {
     public:
-    Model* model;
+    ModelMaterial(Model* _model) : model(_model) {};
     t_model_material_attributes attributes;
     DynamicConfig config;
+    Model* getModel() const;
+    
+    private:
+    Model* model;
 };
 
 class ModelObject
 {
     public:
-    Model* model;
     std::string input_file;
     std::vector<ModelInstance*> instances;
     std::vector<ModelVolume*> volumes;
     DynamicConfig config;
     t_layer_height_ranges layer_height_ranges;
+    Vector origin_translation;  // translation vector applied by center_around_origin() 
     
-    ModelObject();
+    ModelObject(Model* _model) : model(_model) {};
+    ModelObject(Model* _model, const ModelObject &object);
     ~ModelObject();
+    ModelInstance* add_instance();
     ModelInstance* add_instance(const ModelInstance &instance);
+    ModelVolume* add_volume();
     ModelVolume* add_volume(const ModelVolume &volume);
+    void delete_volume(size_t volume_idx);
     void delete_last_instance();
     void raw_mesh(TriangleMesh* mesh) const;
     void mesh(TriangleMesh* mesh) const;
-    void instance_bounding_box(size_t instance_idx, BoundingBox* bb) const;
+    void bounding_box(BoundingBoxf3* bb);
+    void instance_bounding_box(size_t instance_idx, BoundingBoxf3* bb) const;
     void center_around_origin();
     void translate(coordf_t x, coordf_t y, coordf_t z);
     size_t materials_count() const;
@@ -85,28 +98,38 @@ class ModelObject
     bool needed_repair() const;
     
     private:
-    BoundingBox bb;
+    Model* model;
+    BoundingBoxf bb;
     void update_bounding_box();
 };
 
 class ModelVolume
 {
     public:
-    ModelObject* object;
+    ModelVolume(ModelObject* _object) : object(_object), modifier(false) {};
     t_model_material_id material_id;
     TriangleMesh mesh;
+    bool modifier;
+    
+    ModelMaterial* assign_unique_material();
+    
+    private:
+    ModelObject* object;
 };
 
 class ModelInstance
 {
     public:
-    ModelObject* object;
     double rotation;
     double scaling_factor;
     Pointf offset;
     
+    ModelInstance(ModelObject* _object) : object(_object), rotation(0), scaling_factor(1) {};
     void transform_mesh(TriangleMesh* mesh, bool dont_translate) const;
     void transform_polygon(Polygon* polygon) const;
+    
+    private:
+    ModelObject* object;
 };
 
 }