diff --git a/xs/src/libslic3r/Model.cpp b/xs/src/libslic3r/Model.cpp
index d3393250e..9b21c23b1 100644
--- a/xs/src/libslic3r/Model.cpp
+++ b/xs/src/libslic3r/Model.cpp
@@ -211,16 +211,6 @@ Model::center_instances_around_point(const Pointf &point)
     }
 }
 
-void
-Model::align_instances_to_origin()
-{
-    BoundingBoxf3 bb = this->bounding_box();
-    
-    Pointf new_center = (Pointf)bb.size();
-    new_center.translate(-new_center.x/2, -new_center.y/2);
-    this->center_instances_around_point(new_center);
-}
-
 void
 Model::translate(coordf_t x, coordf_t y, coordf_t z)
 {
@@ -634,6 +624,16 @@ ModelObject::instance_bounding_box(size_t instance_idx) const
     }
     return bb;
 }
+	
+void
+Model::align_instances_to_origin()
+{
+    BoundingBoxf3 bb = this->bounding_box();
+    
+    Pointf new_center = (Pointf)bb.size();
+    new_center.translate(-new_center.x/2, -new_center.y/2);
+    this->center_instances_around_point(new_center);
+}
 
 void
 ModelObject::align_to_ground()
diff --git a/xs/src/libslic3r/Model.hpp b/xs/src/libslic3r/Model.hpp
index fed54b601..d20821e73 100644
--- a/xs/src/libslic3r/Model.hpp
+++ b/xs/src/libslic3r/Model.hpp
@@ -28,221 +28,536 @@ typedef std::vector<ModelObject*> ModelObjectPtrs;
 typedef std::vector<ModelVolume*> ModelVolumePtrs;
 typedef std::vector<ModelInstance*> ModelInstancePtrs;
 
-// The print bed content.
-// Description of a triangular model with multiple materials, multiple instances with various affine transformations
-// and with multiple modifier meshes.
-// A model groups multiple objects, each object having possibly multiple instances,
-// all objects may share mutliple materials.
+
+/// Model Class representing the print bed content
+/// Description of a triangular model with multiple materials, multiple instances with various affine transformations
+/// and with multiple modifier meshes.
+/// A model groups multiple objects, each object having possibly multiple instances,
+/// all objects may share multiple materials.
 class Model
 {
     public:
-    // Materials are owned by a model and referenced by objects through t_model_material_id.
-    // Single material may be shared by multiple models.
     ModelMaterialMap materials;
-    // Objects are owned by a model. Each model may have multiple instances, each instance having its own transformation (shift, scale, rotation).
+    ///< Materials are owned by a model and referenced by objects through t_model_material_id.
+    ///< Single material may be shared by multiple models.
+
     ModelObjectPtrs objects;
-    
+    ///< Objects are owned by a model. Each object may have multiple instances
+    ///< , each instance having its own transformation (shift, scale, rotation).
+
+    /// Model constructor.
     Model();
+
+    /// Model constructor.
+    /// \param other Model the model to be copied
     Model(const Model &other);
+
+    /// = Operator overloading.
+    /// \param other Model the model to be copied
+    /// \return Model& the current Model to enable operator cascading
     Model& operator= (Model other);
+
+    /// Swap objects and materials with another model.
+    /// \param other Model the model to be swapped with
     void swap(Model &other);
+
+    /// Model destructor
     ~Model();
+
+    /// Read a model from file.
+    /// This function supports the following formats (STL, OBJ, AMF), It auto-detects the file format from the file name suffix.
+    /// \param  input_file std::string the file path expressed in UTF-8
+    /// \return Model the read Model
     static Model read_from_file(std::string input_file);
+
+    /// Create a new object and add it to the current Model.
+    /// \return ModelObject* a pointer to the new Model
     ModelObject* add_object();
+
+    /// Create a new object and add it to the current Model.
+    /// This function copies another model object
+    /// \param other ModelObject the ModelObject to be copied
+    /// \param copy_volumes if you also want to copy volumes of the other object. By default = true
+    /// \return ModelObject* a pointer to the new ModelObject
     ModelObject* add_object(const ModelObject &other, bool copy_volumes = true);
+
+    /// Delete a ModelObject from the current Model.
+    /// \param idx size_t the index of the desired ModelObject
     void delete_object(size_t idx);
+
+    /// Delete all ModelObjects found in the current Model.
     void clear_objects();
-    
+
+    /// Add a new ModelMaterial to the model.
+    /// \param material_id t_model_material_id the id of the new ModelMaterial to be added
+    /// \return ModelMaterial* a pointer to the new ModelMaterial
     ModelMaterial* add_material(t_model_material_id material_id);
+
+    /// Add a new ModelMaterial to the current Model.
+    /// This function copies another ModelMaterial, It also delete the current ModelMaterial carrying the same
+    /// material id in the map.
+    /// \param material_id t_model_material_id the id of the new ModelMaterial to be added
+    /// \param other ModelMaterial the model material to be copied
+    /// \return ModelMaterial* a pointer to the new ModelMaterial
     ModelMaterial* add_material(t_model_material_id material_id, const ModelMaterial &other);
+
+    /// Get the ModelMaterial object instance having a certain material id.
+    /// Returns null if the ModelMaterial object instance is not found.
+    /// \param material_id t_model_material_id the id of the needed ModelMaterial object instance
+    /// \return ModelMaterial* a pointer to the ModelMaterial object instance or null if not found
     ModelMaterial* get_material(t_model_material_id material_id);
+
+    /// Delete a ModelMaterial carrying a certain material id if found.
+    /// \param material_id t_model_material_id the id of the ModelMaterial to be deleted
     void delete_material(t_model_material_id material_id);
+
+    /// Delete all the ModelMaterial objects found in the current Model.
     void clear_materials();
+
+    /// Check if any ModelObject has no ModelInstances.
+    /// \return bool true means there exists at least one ModelObject with no ModelInstance objects
     bool has_objects_with_no_instances() const;
+
+    /// Add a new ModelInstance to each ModelObject having no ModelInstance objects
+    /// \return bool
     bool add_default_instances();
+
+    /// Get the bounding box of the transformed instances.
+    /// \return BoundingBoxf3 a bounding box object.
     BoundingBoxf3 bounding_box() const;
+
+    /// Repair the ModelObjects of the current Model.
+    /// This function calls repair function on each TriangleMesh of each model object volume
     void repair();
+
+    /// Center the total bounding box of the instances around a point.
+    /// This transformation works in the XY plane only and no transformation in Z is performed.
+    /// \param point pointf object to center the model instances of model objects around
     void center_instances_around_point(const Pointf &point);
-    void align_instances_to_origin();
+
+    /// Translate each ModelObject with x, y, z units.
+    /// \param x coordf_t units in the x direction
+    /// \param y coordf_t units in the y direction
+    /// \param z coordf_t units in the z direction
     void translate(coordf_t x, coordf_t y, coordf_t z);
+
+    /// Flatten all ModelInstances to a single mesh
+    /// after performing instance transformations (if the object was rotated or translated).
+    /// \return TriangleMesh a single TriangleMesh object
     TriangleMesh mesh() const;
+
+    /// Flatten all ModelVolumes to a single mesh without any extra processing (i.e. without applying any instance duplication and/or transformation).
+    /// \return TriangleMesh a single TriangleMesh object
     TriangleMesh raw_mesh() const;
+
+    /// Arrange ModelInstances. ModelInstances of the same ModelObject do not preserve their relative positions.
+    /// It uses the given BoundingBoxf as a hint, but falls back to free arrangement if it's not possible to fit all the parts in it.
+    /// \param sizes Pointfs& number of parts
+    /// \param dist coordf_t distance between cells
+    /// \param bb BoundingBoxf* (optional) pointer to the bounding box of the area to fill
+    /// \param out Pointfs& vector of the output positions
+    /// \return bool whether the function finished arranging objects or it is impossible to arrange
     bool _arrange(const Pointfs &sizes, coordf_t dist, const BoundingBoxf* bb, Pointfs &out) const;
+
+    /// Arrange ModelObjects preserving their ModelInstance count but altering their ModelInstance positions.
+    /// \param dist coordf_t distance between cells
+    /// \param bb BoundingBoxf* (optional) pointer to the bounding box of the area to fill
+    /// \return bool whether the function finished arranging objects or it is impossible to arrange
     bool arrange_objects(coordf_t dist, const BoundingBoxf* bb = NULL);
-    // Croaks if the duplicated objects do not fit the print bed.
+
+    /// Duplicate the ModelInstances of each ModelObject as a whole preserving their relative positions.
+    /// This function croaks if the duplicated objects do not fit the print bed.
+    /// \param copies_num size_t number of copies
+    /// \param dist coordf_t distance between cells
+    /// \param bb BoundingBoxf* (optional) pointer to the bounding box of the area to fill
     void duplicate(size_t copies_num, coordf_t dist, const BoundingBoxf* bb = NULL);
+
+    /// Duplicate each entire ModelInstances of the each ModelObject as a whole.
+    /// This function will append more instances to each object
+    /// and then calls arrange_objects() function to automatically rearrange everything.
+    /// \param copies_num size_t number of copies
+    /// \param dist coordf_t distance between cells
+    /// \param bb BoundingBoxf* (optional) pointer to the bounding box of the area to fill
     void duplicate_objects(size_t copies_num, coordf_t dist, const BoundingBoxf* bb = NULL);
+
+
+    /// Duplicate a single ModelObject and arranges them on a grid.
+    /// Grid duplication is not supported with multiple objects. It throws an exception if there is more than one ModelObject.
+    /// It also throws an exception if there are no ModelObjects in the current Model.
+    /// \param x size_t number of duplicates in x direction
+    /// \param y size_t offset  number of duplicates in y direction
+    /// \param dist coordf_t distance supposed to be between the duplicated ModelObjects
     void duplicate_objects_grid(size_t x, size_t y, coordf_t dist);
+
+    /// This function calls the print_info() function of each ModelObject.
     void print_info() const;
+
+    /// Check to see if the current Model has characteristics of having multiple parts (usually multiple volumes, etc).
+    /// \return bool
     bool looks_like_multipart_object() const;
+
+
+    /// Take all of the ModelObjects in the current Model and combines them into a single ModelObject
     void convert_multipart_object();
 };
 
-// Material, which may be shared across multiple ModelObjects of a single Model.
+/// Model Material class
+/// Material, which may be shared across multiple ModelObjects of a single Model.
 class ModelMaterial
 {
     friend class Model;
     public:
-    // Attributes are defined by the AMF file format, but they don't seem to be used by Slic3r for any purpose.
     t_model_material_attributes attributes;
-    // Dynamic configuration storage for the object specific configuration values, overriding the global configuration.
-    DynamicPrintConfig config;
+    ///< Attributes are defined by the AMF file format, but they don't seem to be used by Slic3r for any purpose.
 
+    DynamicPrintConfig config;
+    ///< Dynamic configuration storage for the object specific configuration values, overriding the global configuration.
+
+    /// Get the parent model owing this material
+    /// \return Model* the onwer Model
     Model* get_model() const { return this->model; };
+
+    /// Apply attributes defined by the AMF file format
+    /// \param attributes t_model_material_attributes the attributes map
     void apply(const t_model_material_attributes &attributes);
-    
+
     private:
-    // Parent, owning this material.
-    Model* model;
-    
+    Model* model; ///<Parent, owning this material.
+
+    /// Constructor
+    /// \param model the parent model owning this material.
     ModelMaterial(Model *model);
+
+    /// Constructor
+    /// \param model Model* the parent model owning this material.
+    /// \param other ModelMaterial& the other model material to be copied
     ModelMaterial(Model *model, const ModelMaterial &other);
 };
 
-// A printable object, possibly having multiple print volumes (each with its own set of parameters and materials),
-// and possibly having multiple modifier volumes, each modifier volume with its set of parameters and materials.
-// Each ModelObject may be instantiated mutliple times, each instance having different placement on the print bed,
-// different rotation and different uniform scaling.
+/// Model Object class
+/// A printable object, possibly having multiple print volumes (each with its own set of parameters and materials),
+/// and possibly having multiple modifier volumes, each modifier volume with its set of parameters and materials.
+/// Each ModelObject may be instantiated multiple times, each instance having different placement on the print bed,
+/// different rotation and different uniform scaling.
 class ModelObject
 {
     friend class Model;
     public:
     std::string name;
-    std::string input_file;
-    // Instances of this ModelObject. Each instance defines a shift on the print bed, rotation around the Z axis and a uniform scaling.
-    // Instances are owned by this ModelObject.
-    ModelInstancePtrs instances;
-    // Printable and modifier volumes, each with its material ID and a set of override parameters.
-    // ModelVolumes are owned by this ModelObject.
-    ModelVolumePtrs volumes;
-    // Configuration parameters specific to a single ModelObject, overriding the global Slic3r settings.
-    DynamicPrintConfig config;
-    // Variation of a layer thickness for spans of Z coordinates.
-    t_layer_height_ranges layer_height_ranges;
+    ///< This ModelObject name.
+
+    std::string input_file;
+    ///< Input file path.
+
+    ModelInstancePtrs instances;
+    ///< Instances of this ModelObject. Each instance defines a shift on the print bed, rotation around the Z axis and a uniform scaling.
+    ///< Instances are owned by this ModelObject.
+
+    ModelVolumePtrs volumes;
+    ///< Printable and modifier volumes, each with its material ID and a set of override parameters.
+    ///< ModelVolumes are owned by this ModelObject.
+
+    DynamicPrintConfig config; ///< Configuration parameters specific to a single ModelObject, overriding the global Slic3r settings.
+
+
+    t_layer_height_ranges layer_height_ranges; ///< Variation of a layer thickness for spans of Z coordinates.
 
-    /* This vector accumulates the total translation applied to the object by the
-        center_around_origin() method. Callers might want to apply the same translation
-        to new volumes before adding them to this object in order to preserve alignment
-        when user expects that. */
     Pointf3 origin_translation;
-    
+    ///< This vector accumulates the total translation applied to the object by the
+    ///< center_around_origin() method. Callers might want to apply the same translation
+    ///< to new volumes before adding them to this object in order to preserve alignment
+    ///< when user expects that.
+
     // these should be private but we need to expose them via XS until all methods are ported
     BoundingBoxf3 _bounding_box;
     bool _bounding_box_valid;
-    
+
+    ///  Get the owning parent Model.
+    /// \return parent Model* pointer to the owner Model
     Model* get_model() const { return this->model; };
-    
+
+    /// Add a new ModelVolume to the current ModelObject. The mesh is copied into the newly created ModelVolume.
+    /// \param mesh TriangularMesh
+    /// \return ModelVolume* pointer to the new volume
     ModelVolume* add_volume(const TriangleMesh &mesh);
+
+    /// Add a new ModelVolume to the current ModelObject.
+    /// \param volume the ModelVolume object to be copied
+    /// \return ModelVolume* pointer to the new volume
     ModelVolume* add_volume(const ModelVolume &volume);
+
+    /// Delete a ModelVolume object.
+    /// \param idx size_t the index of the ModelVolume to be deleted
     void delete_volume(size_t idx);
+
+    /// Delete all ModelVolumes in the
     void clear_volumes();
 
+    /// Add a new ModelInstance to the current ModelObject.
+    /// \return ModelInstance* a pointer to the new instance
     ModelInstance* add_instance();
+
+    /// Add a new ModelInstance to the current ModelObject.
+    /// \param instance the ModelInstance to be copied
+    /// \return ModelInstance* a pointer to the new instance
     ModelInstance* add_instance(const ModelInstance &instance);
+
+    /// Delete a ModelInstance.
+    /// \param idx size_t the index of the ModelInstance to be deleted
     void delete_instance(size_t idx);
+
+    /// Delete the last created ModelInstance object.
     void delete_last_instance();
+
+    /// Delete all ModelInstance objects found in the current ModelObject.
     void clear_instances();
 
+    /// Get the bounding box of the *transformed* instances.
     BoundingBoxf3 bounding_box();
+
+    /// Invalidate the bounding box in the current ModelObject.
     void invalidate_bounding_box();
 
+    /// Repair all TriangleMesh objects found in each ModelVolume.
     void repair();
+
+    /// Flatten all volumes and instances into a single mesh and applying all the ModelInstances transformations.
     TriangleMesh mesh() const;
+
+    /// Flatten all volumes into a single mesh.
     TriangleMesh raw_mesh() const;
+
+    /// Get the raw bounding box.
+    /// This function croaks when there are no ModelInstances for this ModelObject
+    /// \return BoundingBoxf3
     BoundingBoxf3 raw_bounding_box() const;
+
+    /// Get the bounding box of the *transformed* given instance.
+    /// \param instance_idx size_t the index of the ModelInstance in the ModelInstance vector
+    /// \return BoundingBoxf3 the bounding box at the given index
     BoundingBoxf3 instance_bounding_box(size_t instance_idx) const;
+
+    /// Align the current ModelObject to ground by translating the ModelVolumes in the z axis the needed units.
     void align_to_ground();
+
+    /// Center the current ModelObject to origin by translating the ModelVolumes
     void center_around_origin();
+    void align_instances_to_origin();
+
+    /// Translate the current ModelObject by translating ModelVolumes with (x,y,z) units.
+    /// This function calls translate(coordf_t x, coordf_t y, coordf_t z) to translate every TriangleMesh in each ModelVolume.
+    /// \param vector Vectorf3 the translation vector
     void translate(const Vectorf3 &vector);
+
+    /// Translate the current ModelObject by translating ModelVolumes with (x,y,z) units.
+    /// \param x coordf_t the x units
+    /// \param y coordf_t the y units
+    /// \param z coordf_t the z units
     void translate(coordf_t x, coordf_t y, coordf_t z);
+
+    /// Scale the current ModelObject by scaling its ModelVolumes.
+    /// This function calls scale(const Pointf3 &versor) to scale every TriangleMesh in each ModelVolume.
+    /// \param factor float the scaling factor
     void scale(float factor);
+
+    /// Scale the current ModelObject by scaling its ModelVolumes.
+    /// \param versor Pointf3 the scaling factor in a 3d vector.
     void scale(const Pointf3 &versor);
+
+    /// Scale the current ModelObject to fit by altering the scaling factor of ModelInstances.
+    /// It operates on the total size by duplicating the object according to all the instances.
+    /// \param size Sizef3 the size vector
     void scale_to_fit(const Sizef3 &size);
+
+    /// Rotate the current ModelObject by rotating ModelVolumes.
+    /// \param angle float the angle in radians
+    /// \param axis Axis the axis to be rotated around
     void rotate(float angle, const Axis &axis);
+
+    /// Mirror the current Model around a certain axis.
+    /// \param axis Axis enum member
     void mirror(const Axis &axis);
+
+    /// Transform the current ModelObject by a certain ModelInstance attributes.
+    /// Inverse transformation is applied to all the ModelInstances, so that the final size/position/rotation of the transformed objects doesn't change.
+    /// \param instance ModelInstance the instance used to transform the current ModelObject
+    /// \param dont_translate bool whether to translate the current ModelObject or not
     void transform_by_instance(ModelInstance instance, bool dont_translate = false);
+
+    /// Get the number of the unique ModelMaterial objects in this ModelObject.
+    /// \return size_t the materials count
     size_t materials_count() const;
+
+    /// Get the number of the facets found in all ModelVolume objects in this ModelObject which are not modifier volumes.
+    /// \return size_t the facets count
     size_t facets_count() const;
+
+    /// Know whether there exists a TriangleMesh object that needed repair or not.
+    /// \return bool
     bool needed_repair() const;
+
+    /// Cut (Slice) the current ModelObject along a certain axis at a certain coordinate.
+    /// \param axis Axis the axis to slice at (X = 0 or Y or Z)
+    /// \param z coordf_t the point at the certain axis to cut(slice) the Model at
+    /// \param model Model* pointer to the Model which will get the resulting objects added
     void cut(Axis axis, coordf_t z, Model* model) const;
+
+    /// Split the meshes of the ModelVolume in this ModelObject if there exists only one ModelVolume in this ModelObject.
+    /// \param new_objects ModelObjectPtrs the generated ModelObjects after the single ModelVolume split
     void split(ModelObjectPtrs* new_objects);
+
+    /// Update the bounding box in this ModelObject
     void update_bounding_box();   // this is a private method but we expose it until we need to expose it via XS
+
+    /// Print the current info of this ModelObject
     void print_info() const;
-    
+
     private:
-    // Parent object, owning this ModelObject.
-    Model* model;
-    
+    Model* model; ///< Parent object, owning this ModelObject.
+
+    /// Constructor
+    /// \param model Model the owner Model.
     ModelObject(Model *model);
+
+    /// Constructor
+    /// \param model Model the owner Model.
+    /// \param other ModelObject the other ModelObject to be copied
+    /// \param copy_volumes bool whether to also copy its volumes or not, by default = true
     ModelObject(Model *model, const ModelObject &other, bool copy_volumes = true);
+
+    /// = Operator overloading
+    /// \param other ModelObject the other ModelObject to be copied
+    /// \return ModelObject& the current ModelObject to enable operator cascading
     ModelObject& operator= (ModelObject other);
+
+    /// Swap the attributes between another ModelObject
+    /// \param other ModelObject the other ModelObject to be swapped with.
     void swap(ModelObject &other);
+
+    /// Destructor
     ~ModelObject();
 };
 
-// An object STL, or a modifier volume, over which a different set of parameters shall be applied.
-// ModelVolume instances are owned by a ModelObject.
+/// An object STL, or a modifier volume, over which a different set of parameters shall be applied.
+/// ModelVolume instances are owned by a ModelObject.
 class ModelVolume
 {
     friend class ModelObject;
     public:
-    std::string name;
-    // The triangular model.
-    TriangleMesh mesh;
-    // Configuration parameters specific to an object model geometry or a modifier volume, 
-    // overriding the global Slic3r settings and the ModelObject settings.
+
+    std::string name;   ///< Name of this ModelVolume object
+    TriangleMesh mesh;  ///< The triangular model.
     DynamicPrintConfig config;
-    // Is it an object to be printed, or a modifier volume?
-    bool modifier;
-    
-    // A parent object owning this modifier volume.
+    ///< Configuration parameters specific to an object model geometry or a modifier volume,
+    ///< overriding the global Slic3r settings and the ModelObject settings.
+
+    bool modifier;  ///< Is it an object to be printed, or a modifier volume?
+
+    /// Get the parent object owning this modifier volume.
+    /// \return ModelObject* pointer to the owner ModelObject
     ModelObject* get_object() const { return this->object; };
+
+    /// Get the material id of this ModelVolume object
+    /// \return t_model_material_id the material id string
     t_model_material_id material_id() const;
+
+    /// Set the material id to this ModelVolume object
+    /// \param material_id t_model_material_id the id of the material
     void material_id(t_model_material_id material_id);
+
+    /// Get the current ModelMaterial in this ModelVolume object
+    /// \return ModelMaterial* a pointer to the ModelMaterial
     ModelMaterial* material() const;
+
+    /// Add a new ModelMaterial to this ModelVolume
+    /// \param material_id t_model_material_id the id of the material to be added
+    /// \param material ModelMaterial the material to be coppied
     void set_material(t_model_material_id material_id, const ModelMaterial &material);
-    
+
+    /// Add a unique ModelMaterial to the current ModelVolume
+    /// \return ModelMaterial* pointer to the new ModelMaterial
     ModelMaterial* assign_unique_material();
-    
+
     private:
-    // Parent object owning this ModelVolume.
+    ///< Parent object owning this ModelVolume.
     ModelObject* object;
+    ///< The id of the this ModelVolume
     t_model_material_id _material_id;
-    
+
+    /// Constructor
+    /// \param object ModelObject* pointer to the owner ModelObject
+    /// \param mesh TriangleMesh the mesh of the new ModelVolume object
     ModelVolume(ModelObject *object, const TriangleMesh &mesh);
+
+    /// Constructor
+    /// \param object ModelObject* pointer to the owner ModelObject
+    /// \param other ModelVolume the ModelVolume object to be copied
     ModelVolume(ModelObject *object, const ModelVolume &other);
+
+    /// = Operator overloading
+    /// \param other ModelVolume a volume to be copied in the current ModelVolume object
+    /// \return ModelVolume& the current ModelVolume to enable operator cascading
     ModelVolume& operator= (ModelVolume other);
+
+    /// Swap attributes between another ModelVolume object
+    /// \param other ModelVolume the other volume object
     void swap(ModelVolume &other);
 };
 
-// A single instance of a ModelObject.
-// Knows the affine transformation of an object.
+/// A single instance of a ModelObject.
+/// Knows the affine transformation of an object.
 class ModelInstance
 {
     friend class ModelObject;
     public:
-    double rotation;            // Rotation around the Z axis, in radians around mesh center point
-    double scaling_factor;
-    Pointf offset;              // in unscaled coordinates
-    
+    double rotation;            ///< Rotation around the Z axis, in radians around mesh center point
+    double scaling_factor;      ///< scaling factor
+    Pointf offset;              ///< offset in unscaled coordinates
+
+    /// Get the owning ModelObject
+    /// \return ModelObject* pointer to the owner ModelObject
     ModelObject* get_object() const { return this->object; };
 
-    // To be called on an external mesh
+    /// Transform an external TriangleMesh object
+    /// \param mesh TriangleMesh* pointer to the the mesh
+    /// \param dont_translate bool whether to translate the mesh or not
     void transform_mesh(TriangleMesh* mesh, bool dont_translate = false) const;
-    // Calculate a bounding box of a transformed mesh. To be called on an external mesh.
+
+    /// Calculate a bounding box of a transformed mesh. To be called on an external mesh.
+    /// \param mesh TriangleMesh* pointer to the the mesh
+    /// \param dont_translate bool whether to translate the bounding box or not
+    /// \return BoundingBoxf3 the bounding box after transformation
     BoundingBoxf3 transform_mesh_bounding_box(const TriangleMesh* mesh, bool dont_translate = false) const;
-    // Transform an external bounding box.
+
+    /// Transform an external bounding box.
+    /// \param bbox BoundingBoxf3 the bounding box to be transformed
+    /// \param dont_translate bool whether to translate the bounding box or not
+    /// \return BoundingBoxf3 the bounding box after transformation
     BoundingBoxf3 transform_bounding_box(const BoundingBoxf3 &bbox, bool dont_translate = false) const;
-    // To be called on an external polygon. It does not translate the polygon, only rotates and scales.
+
+    /// Rotate or scale an external polygon. It does not translate the polygon.
+    /// \param polygon Polygon* a pointer to the Polygon
     void transform_polygon(Polygon* polygon) const;
-    
+
     private:
-    // Parent object, owning this instance.
-    ModelObject* object;
-    
+    ModelObject* object; ///< Parent object, owning this instance.
+
+    /// Constructor
+    /// \param object ModelObject* pointer to the owner ModelObject
     ModelInstance(ModelObject *object);
+
+    /// Constructor
+    /// \param object ModelObject* pointer to the owner ModelObject
+    /// \param other ModelInstance an instance to be copied in the new ModelInstance object
     ModelInstance(ModelObject *object, const ModelInstance &other);
+
+    /// = Operator overloading
+    /// \param other ModelInstance an instance to be copied in the current ModelInstance object
+    /// \return ModelInstance& the current ModelInstance to enable operator cascading
     ModelInstance& operator= (ModelInstance other);
+
+    /// Swap attributes between another ModelInstance object
+    /// \param other ModelInstance& the other instance object
     void swap(ModelInstance &other);
 };
 
diff --git a/xs/xsp/Model.xsp b/xs/xsp/Model.xsp
index a53065236..6331fa7f8 100644
--- a/xs/xsp/Model.xsp
+++ b/xs/xsp/Model.xsp
@@ -82,7 +82,6 @@
     Clone<BoundingBoxf3> bounding_box();
     void center_instances_around_point(Pointf* point)
         %code%{ THIS->center_instances_around_point(*point); %};
-    void align_instances_to_origin();
     void translate(double x, double y, double z);
     Clone<TriangleMesh> mesh();
     Clone<TriangleMesh> raw_mesh();
@@ -209,6 +208,7 @@ ModelMaterial::attributes()
     bool needed_repair() const;
     int materials_count() const;
     int facets_count();
+    void align_instances_to_origin();
     void align_to_ground();
     void center_around_origin();
     void translate(double x, double y, double z);