mesh_bsurfaces.py

                    # check for zero angles, not sure if it is a great fix
                    if vec_A.length != 0 and vec_B.length != 0:
                        angle = vec_A.angle(vec_B) / pi
                        edge_new_length = (Vector(verts_middle_position_co) - sp[1][i]).length
                    else:
                        angle = 0
                        edge_new_length = 0

                    # If after moving the verts to the middle point, the segment doesn't stretch too much
                    if edge_new_length <= loop_segment_dist * 1.5 * \
                       self.join_stretch_factor and angle < 0.25 * self.join_stretch_factor:

                        # Avoid joining when the actual loop must be merged with the original mesh
                        if not (self.selection_U_exists and i == 0) and \
                           not (self.selection_U2_exists and i == len(surface_splines_parsed[0]) - 1):

                            # Change the coords of both verts to the middle position
                            surface_splines_parsed[0][i] = verts_middle_position_co
                            surface_splines_parsed[len(surface_splines_parsed) - 1][i] = verts_middle_position_co

        # Delete object with control points and object from grease pencil conversion
        bpy.ops.object.delete({"selected_objects": [ob_ctrl_pts]})

        bpy.ops.object.delete({"selected_objects": splines_U_objects})

        # Generate surface

        # Get all verts coords
        all_surface_verts_co = []
        for i in range(0, len(surface_splines_parsed)):
            # Get coords of all verts and make a list with them
            for pt_co in surface_splines_parsed[i]:
                all_surface_verts_co.append(pt_co)

        # Define verts for each face
        all_surface_faces = []
        for i in range(0, len(all_surface_verts_co) - len(surface_splines_parsed[0])):
            if ((i + 1) / len(surface_splines_parsed[0]) != int((i + 1) / len(surface_splines_parsed[0]))):
                all_surface_faces.append(
                            [i + 1, i, i + len(surface_splines_parsed[0]),
                            i + len(surface_splines_parsed[0]) + 1]
                            )
        # Build the mesh
        surf_me_name = "SURFSKIO_surface"
        me_surf = bpy.data.meshes.new(surf_me_name)
        me_surf.from_pydata(all_surface_verts_co, [], all_surface_faces)
        ob_surface = object_utils.object_data_add(context, me_surf)
        ob_surface.location = (0.0, 0.0, 0.0)
        ob_surface.rotation_euler = (0.0, 0.0, 0.0)
        ob_surface.scale = (1.0, 1.0, 1.0)

        # Select all the "unselected but participating" verts, from closed selection
        # or double selections with middle-vertex, for later join with remove doubles
        for v_idx in single_unselected_verts:
            self.main_object.data.vertices[v_idx].select = True

        # Join the new mesh to the main object
        ob_surface.select_set(True)
        self.main_object.select_set(True)
        bpy.context.view_layer.objects.active = self.main_object

        bpy.ops.object.join('INVOKE_REGION_WIN')

        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

        bpy.ops.mesh.remove_doubles('INVOKE_REGION_WIN', threshold=0.0001)
        bpy.ops.mesh.normals_make_consistent('INVOKE_REGION_WIN', inside=False)
        bpy.ops.mesh.select_all('INVOKE_REGION_WIN', action='DESELECT')

        self.update()

        return{'FINISHED'}

    def update(self):
        try:
            global global_offset
            shrinkwrap = self.main_object.modifiers["Shrinkwrap"]
            shrinkwrap.offset = global_offset
            bpy.context.scene.bsurfaces.SURFSK_Shrinkwrap_offset = global_offset
        except:
            pass

        try:
            global global_color
            material = makeMaterial("BSurfaceMesh", global_color)
            if self.main_object.data.materials:
                self.main_object.data.materials[0] = material
            else:
                self.main_object.data.materials.append(material)
            bpy.context.scene.bsurfaces.SURFSK_mesh_color = global_color
        except:
            pass

        try:
            global global_in_front
            self.main_object.show_in_front = global_in_front
            bpy.context.scene.bsurfaces.SURFSK_in_front = global_in_front
        except:
            pass

        try:
            global global_show_wire
            self.main_object.show_wire = global_show_wire
            bpy.context.scene.bsurfaces.SURFSK_show_wire = global_show_wire
        except:
            pass

        try:
            global global_shade_smooth
            if global_shade_smooth:
                bpy.ops.object.shade_smooth()
            else:
                bpy.ops.object.shade_flat()
            bpy.context.scene.bsurfaces.SURFSK_shade_smooth = global_shade_smooth
        except:
            pass

        return{'FINISHED'}

    def execute(self, context):

        if bpy.ops.object.mode_set.poll():
            bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='OBJECT')

        try:
            global global_mesh_object
            global_mesh_object = bpy.context.scene.bsurfaces.SURFSK_mesh.name
            bpy.data.objects[global_mesh_object].select_set(True)
            self.main_object = bpy.data.objects[global_mesh_object]
            bpy.context.view_layer.objects.active = self.main_object
            bsurfaces_props = bpy.context.scene.bsurfaces
        except:
            self.report({'WARNING'}, "Specify the name of the object with retopology")
            return{"CANCELLED"}
        bpy.context.view_layer.objects.active = self.main_object

        self.update()

        if not self.is_fill_faces:
            bpy.ops.wm.context_set_value(data_path='tool_settings.mesh_select_mode',
                                         value='True, False, False')

            # Build splines from the "last saved splines".
            last_saved_curve = bpy.data.curves.new('SURFSKIO_last_crv', 'CURVE')
            self.main_splines = bpy.data.objects.new('SURFSKIO_last_crv', last_saved_curve)
            bpy.context.collection.objects.link(self.main_splines)

            last_saved_curve.dimensions = "3D"

            for sp in self.last_strokes_splines_coords:
                spline = self.main_splines.data.splines.new('BEZIER')
                # less one because one point is added when the spline is created
                spline.bezier_points.add(len(sp) - 1)
                for p in range(0, len(sp)):
                    spline.bezier_points[p].co = [sp[p][0], sp[p][1], sp[p][2]]

            bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='OBJECT')

            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            self.main_splines.select_set(True)
            bpy.context.view_layer.objects.active = self.main_splines

            bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='EDIT')

            bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='SELECT')
            # Important to make it vector first and then automatic, otherwise the
            # tips handles get too big and distort the shrinkwrap results later
            bpy.ops.curve.handle_type_set(type='VECTOR')
            bpy.ops.curve.handle_type_set('INVOKE_REGION_WIN', type='AUTOMATIC')
            bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            self.main_splines.name = "SURFSKIO_temp_strokes"

            if self.is_crosshatch:
                strokes_for_crosshatch = True
                strokes_for_rectangular_surface = False
            else:
                strokes_for_rectangular_surface = True
                strokes_for_crosshatch = False

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            if strokes_for_rectangular_surface:
                self.rectangular_surface(context)
            elif strokes_for_crosshatch:
                self.crosshatch_surface_execute(context)

            #Set Shade smooth to new polygons
            bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='OBJECT')
            global global_shade_smooth
            if global_shade_smooth:
                bpy.ops.object.shade_smooth()
            else:
                bpy.ops.object.shade_flat()

            # Delete main splines
            bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='OBJECT')
            if self.keep_strokes:
                self.main_splines.name = "keep_strokes"
                self.main_splines.data.bevel_depth = 0.001
                if "keep_strokes_material" in bpy.data.materials :
                    self.main_splines.data.materials.append(bpy.data.materials["keep_strokes_material"])
                else:
                    mat = bpy.data.materials.new("keep_strokes_material")
                    mat.diffuse_color = (1, 0, 0, 0)
                    mat.specular_color = (1, 0, 0)
                    mat.specular_intensity = 0.0
                    mat.roughness = 0.0
                    self.main_splines.data.materials.append(mat)
            else:
                bpy.ops.object.delete({"selected_objects": [self.main_splines]})

            # Delete grease pencil strokes
            if self.strokes_type == "GP_STROKES" and not self.stopping_errors:
                try:
                    bpy.context.scene.bsurfaces.SURFSK_gpencil.data.layers.active.clear()
                except:
                    pass

            # Delete annotations
            if self.strokes_type == "GP_ANNOTATION" and not self.stopping_errors:
                try:
                    bpy.context.annotation_data.layers.active.clear()
                except:
                    pass

            bsurfaces_props = bpy.context.scene.bsurfaces
            bsurfaces_props.SURFSK_edges_U = self.edges_U
            bsurfaces_props.SURFSK_edges_V = self.edges_V
            bsurfaces_props.SURFSK_cyclic_cross = self.cyclic_cross
            bsurfaces_props.SURFSK_cyclic_follow = self.cyclic_follow
            bsurfaces_props.SURFSK_automatic_join = self.automatic_join
            bsurfaces_props.SURFSK_loops_on_strokes = self.loops_on_strokes
            bsurfaces_props.SURFSK_keep_strokes = self.keep_strokes

            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            self.main_object.select_set(True)
            bpy.context.view_layer.objects.active = self.main_object

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            self.update()

        return{'FINISHED'}

    def invoke(self, context, event):

        if bpy.ops.object.mode_set.poll():
            bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='OBJECT')

        bsurfaces_props = bpy.context.scene.bsurfaces
        self.cyclic_cross = bsurfaces_props.SURFSK_cyclic_cross
        self.cyclic_follow = bsurfaces_props.SURFSK_cyclic_follow
        self.automatic_join = bsurfaces_props.SURFSK_automatic_join
        self.loops_on_strokes = bsurfaces_props.SURFSK_loops_on_strokes
        self.keep_strokes = bsurfaces_props.SURFSK_keep_strokes

        try:
            global global_mesh_object
            global_mesh_object = bpy.context.scene.bsurfaces.SURFSK_mesh.name
            bpy.data.objects[global_mesh_object].select_set(True)
            self.main_object = bpy.data.objects[global_mesh_object]
            bpy.context.view_layer.objects.active = self.main_object
        except:
            self.report({'WARNING'}, "Specify the name of the object with retopology")
            return{"CANCELLED"}

        self.update()

        self.main_object_selected_verts_count = len([v for v in self.main_object.data.vertices if v.select])

        bpy.ops.wm.context_set_value(data_path='tool_settings.mesh_select_mode',
                                     value='True, False, False')

        self.edges_U = bsurfaces_props.SURFSK_edges_U
        self.edges_V = bsurfaces_props.SURFSK_edges_V

        self.is_fill_faces = False
        self.stopping_errors = False
        self.last_strokes_splines_coords = []

        # Determine the type of the strokes
        self.strokes_type = get_strokes_type(context)

        # Check if it will be used grease pencil strokes or curves
        # If there are strokes to be used
        if self.strokes_type == "GP_STROKES" or self.strokes_type == "EXTERNAL_CURVE" or self.strokes_type == "GP_ANNOTATION":
            if self.strokes_type == "GP_STROKES":
                # Convert grease pencil strokes to curve
                global global_gpencil_object
                gp = bpy.data.objects[global_gpencil_object]
                self.original_curve = conver_gpencil_to_curve(self, context, gp, 'GPensil')
                self.using_external_curves = False

            elif self.strokes_type == "GP_ANNOTATION":
                # Convert grease pencil strokes to curve
                gp = bpy.context.annotation_data
                self.original_curve = conver_gpencil_to_curve(self, context, gp, 'Annotation')
                self.using_external_curves = False

            elif self.strokes_type == "EXTERNAL_CURVE":
                global global_curve_object
                self.original_curve = bpy.data.objects[global_curve_object]
                self.using_external_curves = True

            # Make sure there are no objects left from erroneous
            # executions of this operator, with the reserved names used here
            for o in bpy.data.objects:
                if o.name.find("SURFSKIO_") != -1:
                    bpy.ops.object.delete({"selected_objects": [o]})

            bpy.context.view_layer.objects.active = self.original_curve

            bpy.ops.object.duplicate('INVOKE_REGION_WIN')

            self.temporary_curve = bpy.context.view_layer.objects.active

            # Deselect all points of the curve
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
            bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            # Delete splines with only a single isolated point
            for i in range(len(self.temporary_curve.data.splines)):
                sp = self.temporary_curve.data.splines[i]

                if len(sp.bezier_points) == 1:
                    sp.bezier_points[0].select_control_point = True

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
            bpy.ops.curve.delete(type='VERT')
            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            self.temporary_curve.select_set(True)
            bpy.context.view_layer.objects.active = self.temporary_curve

            # Set a minimum number of points for crosshatch
            minimum_points_num = 15

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
            # Check if the number of points of each curve has at least the number of points
            # of minimum_points_num, which is a bit more than the face-loops limit.
            # If not, subdivide to reach at least that number of points
            for i in range(len(self.temporary_curve.data.splines)):
                sp = self.temporary_curve.data.splines[i]

                if len(sp.bezier_points) < minimum_points_num:
                    for bp in sp.bezier_points:
                        bp.select_control_point = True

                    if (len(sp.bezier_points) - 1) != 0:
                        # Formula to get the number of cuts that will make a curve
                        # of N number of points have near to "minimum_points_num"
                        # points, when subdividing with this number of cuts
                        subdivide_cuts = int(
                                    (minimum_points_num - len(sp.bezier_points)) /
                                    (len(sp.bezier_points) - 1)
                                    ) + 1
                    else:
                        subdivide_cuts = 0

                    bpy.ops.curve.subdivide('INVOKE_REGION_WIN', number_cuts=subdivide_cuts)
                    bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='DESELECT')

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            # Detect if the strokes are a crosshatch and do it if it is
            self.crosshatch_surface_invoke(self.temporary_curve)

            if not self.is_crosshatch:
                bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
                self.temporary_curve.select_set(True)
                bpy.context.view_layer.objects.active = self.temporary_curve

                bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

                # Set a minimum number of points for rectangular surfaces
                minimum_points_num = 60

                # Check if the number of points of each curve has at least the number of points
                # of minimum_points_num, which is a bit more than the face-loops limit.
                # If not, subdivide to reach at least that number of points
                for i in range(len(self.temporary_curve.data.splines)):
                    sp = self.temporary_curve.data.splines[i]

                    if len(sp.bezier_points) < minimum_points_num:
                        for bp in sp.bezier_points:
                            bp.select_control_point = True

                        if (len(sp.bezier_points) - 1) != 0:
                            # Formula to get the number of cuts that will make a curve of
                            # N number of points have near to "minimum_points_num" points,
                            # when subdividing with this number of cuts
                            subdivide_cuts = int(
                                        (minimum_points_num - len(sp.bezier_points)) /
                                        (len(sp.bezier_points) - 1)
                                        ) + 1
                        else:
                            subdivide_cuts = 0

                        bpy.ops.curve.subdivide('INVOKE_REGION_WIN', number_cuts=subdivide_cuts)
                        bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='DESELECT')

                bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            # Save coordinates of the actual strokes (as the "last saved splines")
            for sp_idx in range(len(self.temporary_curve.data.splines)):
                self.last_strokes_splines_coords.append([])
                for bp_idx in range(len(self.temporary_curve.data.splines[sp_idx].bezier_points)):
                    coords = self.temporary_curve.matrix_world @ \
                             self.temporary_curve.data.splines[sp_idx].bezier_points[bp_idx].co
                    self.last_strokes_splines_coords[sp_idx].append([coords[0], coords[1], coords[2]])

            # Check for cyclic splines, put the first and last points in the middle of their actual positions
            for sp_idx in range(len(self.temporary_curve.data.splines)):
                if self.temporary_curve.data.splines[sp_idx].use_cyclic_u is True:
                    first_p_co = self.last_strokes_splines_coords[sp_idx][0]
                    last_p_co = self.last_strokes_splines_coords[sp_idx][
                                                            len(self.last_strokes_splines_coords[sp_idx]) - 1
                                                            ]
                    target_co = [
                            (first_p_co[0] + last_p_co[0]) / 2,
                            (first_p_co[1] + last_p_co[1]) / 2,
                            (first_p_co[2] + last_p_co[2]) / 2
                            ]

                    self.last_strokes_splines_coords[sp_idx][0] = target_co
                    self.last_strokes_splines_coords[sp_idx][
                                                            len(self.last_strokes_splines_coords[sp_idx]) - 1
                                                            ] = target_co
            tuple(self.last_strokes_splines_coords)

            # Estimation of the average length of the segments between
            # each point of the grease pencil strokes.
            # Will be useful to determine whether a curve should be made "Cyclic"
            segments_lengths_sum = 0
            segments_count = 0
            random_spline = self.temporary_curve.data.splines[0].bezier_points
            for i in range(0, len(random_spline)):
                if i != 0 and len(random_spline) - 1 >= i:
                    segments_lengths_sum += (random_spline[i - 1].co - random_spline[i].co).length
                    segments_count += 1

            self.average_gp_segment_length = segments_lengths_sum / segments_count

            # Delete temporary strokes curve object
            bpy.ops.object.delete({"selected_objects": [self.temporary_curve]})

            # Set again since "execute()" will turn it again to its initial value
            self.execute(context)

            if not self.stopping_errors:
                # Delete grease pencil strokes
                if self.strokes_type == "GP_STROKES":
                    try:
                        bpy.context.scene.bsurfaces.SURFSK_gpencil.data.layers.active.clear()
                    except:
                        pass

                # Delete annotation strokes
                elif self.strokes_type == "GP_ANNOTATION":
                    try:
                        bpy.context.annotation_data.layers.active.clear()
                    except:
                        pass

                bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
                bpy.ops.object.delete({"selected_objects": [self.original_curve]})
                bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

                return {"FINISHED"}
            else:
                return{"CANCELLED"}

        elif self.strokes_type == "SELECTION_ALONE":
            self.is_fill_faces = True
            created_faces_count = self.fill_with_faces(self.main_object)

            bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

            if created_faces_count == 0:
                self.report({'WARNING'}, "There aren't any strokes attached to the object")
                return {"CANCELLED"}
            else:
                return {"FINISHED"}

        if self.strokes_type == "EXTERNAL_NO_CURVE":
            self.report({'WARNING'}, "The secondary object is not a Curve.")
            return{"CANCELLED"}

        elif self.strokes_type == "MORE_THAN_ONE_EXTERNAL":
            self.report({'WARNING'}, "There shouldn't be more than one secondary object selected.")
            return{"CANCELLED"}

        elif self.strokes_type == "SINGLE_GP_STROKE_NO_SELECTION" or \
             self.strokes_type == "SINGLE_CURVE_STROKE_NO_SELECTION":

            self.report({'WARNING'}, "It's needed at least one stroke and one selection, or two strokes.")
            return{"CANCELLED"}

        elif self.strokes_type == "NO_STROKES":
            self.report({'WARNING'}, "There aren't any strokes attached to the object")
            return{"CANCELLED"}

        elif self.strokes_type == "CURVE_WITH_NON_BEZIER_SPLINES":
            self.report({'WARNING'}, "All splines must be Bezier.")
            return{"CANCELLED"}

        else:
            return{"CANCELLED"}

# ----------------------------
# Init operator
class MESH_OT_SURFSK_init(Operator):
    bl_idname = "mesh.surfsk_init"
    bl_label = "Bsurfaces initialize"
    bl_description = "Add an empty mesh object with useful settings"
    bl_options = {'REGISTER', 'UNDO'}

    def execute(self, context):

        bs = bpy.context.scene.bsurfaces

        if bpy.ops.object.mode_set.poll():
            bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='OBJECT')

        global global_color
        global global_offset
        global global_in_front
        global global_show_wire
        global global_shade_smooth
        global global_mesh_object
        global global_gpencil_object

        if bs.SURFSK_mesh == None:
            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            mesh = bpy.data.meshes.new('BSurfaceMesh')
            mesh_object = object_utils.object_data_add(context, mesh)
            mesh_object.select_set(True)
            bpy.context.view_layer.objects.active = mesh_object

            mesh_object.show_all_edges = True
            global_in_front = bpy.context.scene.bsurfaces.SURFSK_in_front
            mesh_object.show_in_front = global_in_front
            mesh_object.display_type = 'SOLID'
            mesh_object.show_wire = True

            global_shade_smooth = bpy.context.scene.bsurfaces.SURFSK_shade_smooth
            if global_shade_smooth:
                bpy.ops.object.shade_smooth()
            else:
                bpy.ops.object.shade_flat()

            global_show_wire = bpy.context.scene.bsurfaces.SURFSK_show_wire
            mesh_object.show_wire = global_show_wire

            global_color = bpy.context.scene.bsurfaces.SURFSK_mesh_color
            material = makeMaterial("BSurfaceMesh", global_color)
            mesh_object.data.materials.append(material)
            bpy.ops.object.modifier_add(type='SHRINKWRAP')
            modifier = mesh_object.modifiers["Shrinkwrap"]
            if self.active_object is not None:
                modifier.target = self.active_object
                modifier.wrap_method = 'TARGET_PROJECT'
                modifier.wrap_mode = 'OUTSIDE_SURFACE'
                modifier.show_on_cage = True
                global_offset = bpy.context.scene.bsurfaces.SURFSK_Shrinkwrap_offset
                modifier.offset = global_offset

            global_mesh_object = mesh_object.name
            bpy.context.scene.bsurfaces.SURFSK_mesh = bpy.data.objects[global_mesh_object]

            bpy.context.scene.tool_settings.snap_elements = {'FACE'}
            bpy.context.scene.tool_settings.use_snap = True
            bpy.context.scene.tool_settings.use_snap_self = False
            bpy.context.scene.tool_settings.use_snap_align_rotation = True
            bpy.context.scene.tool_settings.use_snap_project = True
            bpy.context.scene.tool_settings.use_snap_rotate = True
            bpy.context.scene.tool_settings.use_snap_scale = True

            bpy.context.scene.tool_settings.use_mesh_automerge = True
            bpy.context.scene.tool_settings.double_threshold = 0.01

        if context.scene.bsurfaces.SURFSK_guide == 'GPencil' and bs.SURFSK_gpencil == None:
            bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
            bpy.ops.object.gpencil_add(radius=1.0, align='WORLD', location=(0.0, 0.0, 0.0), rotation=(0.0, 0.0, 0.0), type='EMPTY')
            bpy.context.scene.tool_settings.gpencil_stroke_placement_view3d = 'SURFACE'
            gpencil_object = bpy.context.scene.objects[bpy.context.scene.objects[-1].name]
            gpencil_object.select_set(True)
            bpy.context.view_layer.objects.active = gpencil_object
            bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='PAINT_GPENCIL')
            global_gpencil_object = gpencil_object.name
            bpy.context.scene.bsurfaces.SURFSK_gpencil = bpy.data.objects[global_gpencil_object]
            gpencil_object.data.stroke_depth_order = '3D'
            bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='PAINT_GPENCIL')
            bpy.ops.wm.tool_set_by_id(name="builtin_brush.Draw")

        if context.scene.bsurfaces.SURFSK_guide == 'Annotation':
            bpy.ops.wm.tool_set_by_id(name="builtin.annotate")
            bpy.context.scene.tool_settings.annotation_stroke_placement_view3d = 'SURFACE'

    def invoke(self, context, event):
        if bpy.context.active_object:
            self.active_object = bpy.context.active_object
        else:
            self.active_object = None

        self.execute(context)

        return {"FINISHED"}

# ----------------------------
# Add modifiers operator
class MESH_OT_SURFSK_add_modifiers(Operator):
    bl_idname = "mesh.surfsk_add_modifiers"
    bl_label = "Add Mirror and others modifiers"
    bl_description = "Add modifiers: Mirror, Shrinkwrap, Subdivision, Solidify"
    bl_options = {'REGISTER', 'UNDO'}

    def execute(self, context):

        bs = bpy.context.scene.bsurfaces

        if bpy.ops.object.mode_set.poll():
            bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='OBJECT')

        if bs.SURFSK_mesh == None:
            self.report({'ERROR_INVALID_INPUT'}, "Please select Mesh of BSurface or click Initialize")
        else:
            mesh_object = bs.SURFSK_mesh

            try:
                mesh_object.select_set(True)
            except:
                self.report({'ERROR_INVALID_INPUT'}, "Mesh of BSurface does not exist")
                return {"CANCEL"}

            bpy.context.view_layer.objects.active = mesh_object

            try:
                shrinkwrap = mesh_object.modifiers["Shrinkwrap"]
                if self.active_object is not None and self.active_object != mesh_object:
                    shrinkwrap.target = self.active_object
                    shrinkwrap.wrap_method = 'TARGET_PROJECT'
                    shrinkwrap.wrap_mode = 'OUTSIDE_SURFACE'
                    shrinkwrap.show_on_cage = True
                    shrinkwrap.offset = bpy.context.scene.bsurfaces.SURFSK_Shrinkwrap_offset
            except:
                bpy.ops.object.modifier_add(type='SHRINKWRAP')
                shrinkwrap = mesh_object.modifiers["Shrinkwrap"]
                if self.active_object is not None and self.active_object != mesh_object:
                    shrinkwrap.target = self.active_object
                    shrinkwrap.wrap_method = 'TARGET_PROJECT'
                    shrinkwrap.wrap_mode = 'OUTSIDE_SURFACE'
                    shrinkwrap.show_on_cage = True
                    shrinkwrap.offset = bpy.context.scene.bsurfaces.SURFSK_Shrinkwrap_offset

            try:
                mirror = mesh_object.modifiers["Mirror"]
                mirror.use_clip = True
            except:
                bpy.ops.object.modifier_add(type='MIRROR')
                mirror = mesh_object.modifiers["Mirror"]
                mirror.use_clip = True

            try:
                _subsurf = mesh_object.modifiers["Subdivision"]
            except:
                bpy.ops.object.modifier_add(type='SUBSURF')
                _subsurf = mesh_object.modifiers["Subdivision"]

            try:
                solidify = mesh_object.modifiers["Solidify"]
                solidify.thickness = 0.01
            except:
                bpy.ops.object.modifier_add(type='SOLIDIFY')
                solidify = mesh_object.modifiers["Solidify"]
                solidify.thickness = 0.01

        return {"FINISHED"}

    def invoke(self, context, event):
        if bpy.context.active_object:
            self.active_object = bpy.context.active_object
        else:
            self.active_object = None

        self.execute(context)

        return {"FINISHED"}

# ----------------------------
# Edit surface operator
class MESH_OT_SURFSK_edit_surface(Operator):
    bl_idname = "mesh.surfsk_edit_surface"
    bl_label = "Bsurfaces edit surface"
    bl_description = "Edit surface mesh"
    bl_options = {'REGISTER', 'UNDO'}

    def execute(self, context):
        if bpy.ops.object.mode_set.poll():
            bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='OBJECT')
        bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
        bpy.context.scene.bsurfaces.SURFSK_mesh.select_set(True)
        bpy.context.view_layer.objects.active = bpy.context.scene.bsurfaces.SURFSK_mesh
        bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='EDIT')
        bpy.ops.wm.tool_set_by_id(name="builtin.select")

    def invoke(self, context, event):
        try:
            global_mesh_object = bpy.context.scene.bsurfaces.SURFSK_mesh.name
            bpy.data.objects[global_mesh_object].select_set(True)
            self.main_object = bpy.data.objects[global_mesh_object]
            bpy.context.view_layer.objects.active = self.main_object
        except:
            self.report({'WARNING'}, "Specify the name of the object with retopology")
            return{"CANCELLED"}

        self.execute(context)

        return {"FINISHED"}

# ----------------------------
# Add strokes operator
class GPENCIL_OT_SURFSK_add_strokes(Operator):
    bl_idname = "gpencil.surfsk_add_strokes"
    bl_label = "Bsurfaces add strokes"
    bl_description = "Add the grease pencil strokes"
    bl_options = {'REGISTER', 'UNDO'}

    def execute(self, context):
        if bpy.ops.object.mode_set.poll():
            bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='OBJECT')
        bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')

        bpy.context.scene.bsurfaces.SURFSK_gpencil.select_set(True)
        bpy.context.view_layer.objects.active = bpy.context.scene.bsurfaces.SURFSK_gpencil
        bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='PAINT_GPENCIL')
        bpy.ops.wm.tool_set_by_id(name="builtin_brush.Draw")

        return{"FINISHED"}

    def invoke(self, context, event):
        try:
            bpy.context.scene.bsurfaces.SURFSK_gpencil.select_set(True)
        except:
            self.report({'WARNING'}, "Specify the name of the object with strokes")
            return{"CANCELLED"}

        self.execute(context)

        return {"FINISHED"}

# ----------------------------
# Edit strokes operator
class GPENCIL_OT_SURFSK_edit_strokes(Operator):
    bl_idname = "gpencil.surfsk_edit_strokes"
    bl_label = "Bsurfaces edit strokes"
    bl_description = "Edit the grease pencil strokes"
    bl_options = {'REGISTER', 'UNDO'}

    def execute(self, context):
        if bpy.ops.object.mode_set.poll():
            bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='OBJECT')
        bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')

        gpencil_object = bpy.context.scene.bsurfaces.SURFSK_gpencil

        gpencil_object.select_set(True)
        bpy.context.view_layer.objects.active = gpencil_object

        bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='EDIT_GPENCIL')
        try:
            bpy.ops.gpencil.select_all(action='SELECT')
        except:
            pass

    def invoke(self, context, event):
        try:
           bpy.context.scene.bsurfaces.SURFSK_gpencil.select_set(True)
        except:
            self.report({'WARNING'}, "Specify the name of the object with strokes")
            return{"CANCELLED"}

        self.execute(context)

        return {"FINISHED"}

# ----------------------------
# Convert annotation to curves operator
class GPENCIL_OT_SURFSK_annotation_to_curves(Operator):
    bl_idname = "gpencil.surfsk_annotations_to_curves"
    bl_label = "Convert annotation to curves"
    bl_description = "Convert annotation to curves for editing"
    bl_options = {'REGISTER', 'UNDO'}

    def execute(self, context):

        if bpy.ops.object.mode_set.poll():
            bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='OBJECT')

        # Convert annotation to curve
        curve = conver_gpencil_to_curve(self, context, None, 'Annotation')

        if curve != None:
            # Delete annotation strokes
            try:
                bpy.context.annotation_data.layers.active.clear()
            except:
                pass

            # Clean up curves
            curve.select_set(True)
            bpy.context.view_layer.objects.active = curve

            bpy.ops.wm.tool_set_by_id(name="builtin.select_box")

        return {"FINISHED"}

    def invoke(self, context, event):
        try:
            strokes = bpy.context.annotation_data.layers.active.active_frame.strokes

            _strokes_num = len(strokes)
        except:
            self.report({'WARNING'}, "Not active annotation")
            return{"CANCELLED"}

        self.execute(context)

        return {"FINISHED"}

# ----------------------------
# Convert strokes to curves operator
class GPENCIL_OT_SURFSK_strokes_to_curves(Operator):
    bl_idname = "gpencil.surfsk_strokes_to_curves"
    bl_label = "Convert strokes to curves"
    bl_description = "Convert grease pencil strokes to curves for editing"
    bl_options = {'REGISTER', 'UNDO'}

    def execute(self, context):

        if bpy.ops.object.mode_set.poll():
            bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='OBJECT')

        # Convert grease pencil strokes to curve
        gp = bpy.context.scene.bsurfaces.SURFSK_gpencil
        curve = conver_gpencil_to_curve(self, context, gp, 'GPensil')

        if curve != None:
            # Delete grease pencil strokes
            try:
                bpy.context.scene.bsurfaces.SURFSK_gpencil.data.layers.active.clear()
            except:
                pass

            # Clean up curves

            curve.select_set(True)
            bpy.context.view_layer.objects.active = curve

            bpy.ops.wm.tool_set_by_id(name="builtin.select_box")

        return {"FINISHED"}

    def invoke(self, context, event):
        try:
           bpy.context.scene.bsurfaces.SURFSK_gpencil.select_set(True)
        except:
            self.report({'WARNING'}, "Specify the name of the object with strokes")
            return{"CANCELLED"}

        self.execute(context)

        return {"FINISHED"}

# ----------------------------
# Add annotation
class GPENCIL_OT_SURFSK_add_annotation(Operator):
    bl_idname = "gpencil.surfsk_add_annotation"
    bl_label = "Bsurfaces add annotation"
    bl_description = "Add annotation"
    bl_options = {'REGISTER', 'UNDO'}

    def execute(self, context):
        bpy.ops.wm.tool_set_by_id(name="builtin.annotate")
        bpy.context.scene.tool_settings.annotation_stroke_placement_view3d = 'SURFACE'

        return{"FINISHED"}

    def invoke(self, context, event):

        self.execute(context)

        return {"FINISHED"}


# ----------------------------
# Edit curve operator
class CURVE_OT_SURFSK_edit_curve(Operator):
    bl_idname = "curve.surfsk_edit_curve"
    bl_label = "Bsurfaces edit curve"
    bl_description = "Edit curve"
    bl_options = {'REGISTER', 'UNDO'}

    def execute(self, context):
        if bpy.ops.object.mode_set.poll():
            bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='OBJECT')
        bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
        bpy.context.scene.bsurfaces.SURFSK_curve.select_set(True)
        bpy.context.view_layer.objects.active = bpy.context.scene.bsurfaces.SURFSK_curve
        bpy.ops.object.mode_set('INVOKE_REGION_WIN', mode='EDIT')

    def invoke(self, context, event):
        try:
            bpy.context.scene.bsurfaces.SURFSK_curve.select_set(True)
        except:
            self.report({'WARNING'}, "Specify the name of the object with curve")
            return{"CANCELLED"}

        self.execute(context)

        return {"FINISHED"}

# ----------------------------
# Reorder splines
class CURVE_OT_SURFSK_reorder_splines(Operator):
    bl_idname = "curve.surfsk_reorder_splines"
    bl_label = "Bsurfaces reorder splines"
    bl_description = "Defines the order of the splines by using grease pencil strokes"
    bl_options = {'REGISTER', 'UNDO'}

    def execute(self, context):
        objects_to_delete = []
        # Convert grease pencil strokes to curve.
        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
        bpy.ops.gpencil.convert('INVOKE_REGION_WIN', type='CURVE', use_link_strokes=False)
        for ob in bpy.context.selected_objects:
            if ob != bpy.context.view_layer.objects.active and ob.name.startswith("GP_Layer"):
                GP_strokes_curve = ob

        # GP_strokes_curve = bpy.context.object
        objects_to_delete.append(GP_strokes_curve)

        bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
        GP_strokes_curve.select_set(True)
        bpy.context.view_layer.objects.active = GP_strokes_curve

        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
        bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='SELECT')
        bpy.ops.curve.subdivide('INVOKE_REGION_WIN', number_cuts=100)
        bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')

        bpy.ops.object.duplicate('INVOKE_REGION_WIN')
        GP_strokes_mesh = bpy.context.object
        objects_to_delete.append(GP_strokes_mesh)

        GP_strokes_mesh.data.resolution_u = 1
        bpy.ops.object.convert(target='MESH', keep_original=False)

        bpy.ops.object.select_all('INVOKE_REGION_WIN', action='DESELECT')
        self.main_curve.select_set(True)
        bpy.context.view_layer.objects.active = self.main_curve

        bpy.ops.object.duplicate('INVOKE_REGION_WIN')
        curves_duplicate_1 = bpy.context.object
        objects_to_delete.append(curves_duplicate_1)

        minimum_points_num = 500

        # Some iterations since the subdivision operator
        # has a limit of 100 subdivisions per iteration
        for x in range(round(minimum_points_num / 100)):
            # Check if the number of points of each curve has at least the number of points
            # of minimum_points_num. If not, subdivide to reach at least that number of points
            for i in range(len(curves_duplicate_1.data.splines)):
                sp = curves_duplicate_1.data.splines[i]

                if len(sp.bezier_points) < minimum_points_num:
                    for bp in sp.bezier_points:
                        bp.select_control_point = True

                    if (len(sp.bezier_points) - 1) != 0:
                        # Formula to get the number of cuts that will make a curve of N
                        # number of points have near to "minimum_points_num" points,
                        # when subdividing with this number of cuts
                        subdivide_cuts = int(
                                (minimum_points_num - len(sp.bezier_points)) /
                                (len(sp.bezier_points) - 1)
                                ) + 1
                    else:
                        subdivide_cuts = 0

                    bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')
                    bpy.ops.curve.subdivide('INVOKE_REGION_WIN', number_cuts=subdivide_cuts)
                    bpy.ops.curve.select_all('INVOKE_REGION_WIN', action='DESELECT')
                    bpy.ops.object.editmode_toggle('INVOKE_REGION_WIN')