mesh_looptools.py

                elif loop[i] != points[j][0]:
                    points[j].append(loop[i])
            if circular:
                if knots[j][0] != knots[j][-1]:
                    knots[j].append(knots[j][0])
        if len(points[1]) == 0:
            knots.pop(1)
            points.pop(1)
        for k in knots:
            all_knots.append(k)
        for p in points:
            all_points.append(p)

    return(all_knots, all_points)


# calculate relative positions compared to first knot
def relax_calculate_t(bm_mod, knots, points, regular):
    all_tknots = []
    all_tpoints = []
    for i in range(len(knots)):
        amount = len(knots[i]) + len(points[i])
        mix  = []
        for j in range(amount):
            if j%2 == 0:
                mix.append([True, knots[i][round(j/2)]])
            elif j == amount-1:
                mix.append([True, knots[i][-1]])
            else:
                mix.append([False, points[i][int(j/2)]])
        len_total = 0
        loc_prev = False
        tknots = []
        tpoints = []
        for m in mix:
            loc = mathutils.Vector(bm_mod.verts[m[1]].co[:])
            if not loc_prev:
                loc_prev = loc
            len_total += (loc - loc_prev).length
            if m[0]:
                tknots.append(len_total)
            else:
                tpoints.append(len_total)
            loc_prev = loc
        if regular:
            tpoints = []
            for p in range(len(points[i])):
                tpoints.append((tknots[p] + tknots[p+1]) / 2)
        all_tknots.append(tknots)
        all_tpoints.append(tpoints)

    return(all_tknots, all_tpoints)


# change the location of the points to their place on the spline
def relax_calculate_verts(bm_mod, interpolation, tknots, knots, tpoints,
points, splines):
    change = []
    move = []
    for i in range(len(knots)):
        for p in points[i]:
            m = tpoints[i][points[i].index(p)]
            if m in tknots[i]:
                n = tknots[i].index(m)
            else:
                t = tknots[i][:]
                t.append(m)
                t.sort()
                n = t.index(m)-1
            if n > len(splines[i]) - 1:
                n = len(splines[i]) - 1
            elif n < 0:
                n = 0

            if interpolation == 'cubic':
                ax, bx, cx, dx, tx = splines[i][n][0]
                x = ax + bx*(m-tx) + cx*(m-tx)**2 + dx*(m-tx)**3
                ay, by, cy, dy, ty = splines[i][n][1]
                y = ay + by*(m-ty) + cy*(m-ty)**2 + dy*(m-ty)**3
                az, bz, cz, dz, tz = splines[i][n][2]
                z = az + bz*(m-tz) + cz*(m-tz)**2 + dz*(m-tz)**3
                change.append([p, mathutils.Vector([x,y,z])])
            else: # interpolation == 'linear'
                a, d, t, u = splines[i][n]
                if u == 0:
                    u = 1e-8
                change.append([p, ((m-t)/u)*d + a])
    for c in change:
        move.append([c[0], (bm_mod.verts[c[0]].co + c[1]) / 2])

    return(move)


##########################################
####### Space functions ##################
##########################################

# calculate relative positions compared to first knot
def space_calculate_t(bm_mod, knots):
    tknots = []
    loc_prev = False
    len_total = 0
    for k in knots:
        loc = mathutils.Vector(bm_mod.verts[k].co[:])
        if not loc_prev:
            loc_prev = loc
        len_total += (loc - loc_prev).length
        tknots.append(len_total)
        loc_prev = loc
    amount = len(knots)
    t_per_segment = len_total / (amount - 1)
    tpoints = [i * t_per_segment for i in range(amount)]

    return(tknots, tpoints)


# change the location of the points to their place on the spline
def space_calculate_verts(bm_mod, interpolation, tknots, tpoints, points,
splines):
    move = []
    for p in points:
        m = tpoints[points.index(p)]
        if m in tknots:
            n = tknots.index(m)
        else:
            t = tknots[:]
            t.append(m)
            t.sort()
            n = t.index(m) - 1
        if n > len(splines) - 1:
            n = len(splines) - 1
        elif n < 0:
            n = 0

        if interpolation == 'cubic':
            ax, bx, cx, dx, tx = splines[n][0]
            x = ax + bx*(m-tx) + cx*(m-tx)**2 + dx*(m-tx)**3
            ay, by, cy, dy, ty = splines[n][1]
            y = ay + by*(m-ty) + cy*(m-ty)**2 + dy*(m-ty)**3
            az, bz, cz, dz, tz = splines[n][2]
            z = az + bz*(m-tz) + cz*(m-tz)**2 + dz*(m-tz)**3
            move.append([p, mathutils.Vector([x,y,z])])
        else: # interpolation == 'linear'
            a, d, t, u = splines[n]
            move.append([p, ((m-t)/u)*d + a])

    return(move)


##########################################
####### Operators ########################
##########################################

# bridge operator
class Bridge(bpy.types.Operator):
    bl_idname = 'mesh.looptools_bridge'
    bl_label = "Bridge / Loft"
    bl_description = "Bridge two, or loft several, loops of vertices"
    bl_options = {'REGISTER', 'UNDO'}

    cubic_strength = bpy.props.FloatProperty(name = "Strength",
        description = "Higher strength results in more fluid curves",
        default = 1.0,
        soft_min = -3.0,
        soft_max = 3.0)
    interpolation = bpy.props.EnumProperty(name = "Interpolation mode",
        items = (('cubic', "Cubic", "Gives curved results"),
            ('linear', "Linear", "Basic, fast, straight interpolation")),
        description = "Interpolation mode: algorithm used when creating "\
            "segments",
        default = 'cubic')
    loft = bpy.props.BoolProperty(name = "Loft",
        description = "Loft multiple loops, instead of considering them as "\
            "a multi-input for bridging",
        default = False)
    loft_loop = bpy.props.BoolProperty(name = "Loop",
        description = "Connect the first and the last loop with each other",
        default = False)
    min_width = bpy.props.IntProperty(name = "Minimum width",
        description = "Segments with an edge smaller than this are merged "\
            "(compared to base edge)",
        default = 0,
        min = 0,
        max = 100,
        subtype = 'PERCENTAGE')
    mode = bpy.props.EnumProperty(name = "Mode",
        items = (('basic', "Basic", "Fast algorithm"), ('shortest',
            "Shortest edge", "Slower algorithm with better vertex matching")),
        description = "Algorithm used for bridging",
        default = 'shortest')
    remove_faces = bpy.props.BoolProperty(name = "Remove faces",
        description = "Remove faces that are internal after bridging",
        default = True)
    reverse = bpy.props.BoolProperty(name = "Reverse",
        description = "Manually override the direction in which the loops "\
                      "are bridged. Only use if the tool gives the wrong " \
                      "result",
        default = False)
    segments = bpy.props.IntProperty(name = "Segments",
        description = "Number of segments used to bridge the gap "\
            "(0 = automatic)",
        default = 1,
        min = 0,
        soft_max = 20)
    twist = bpy.props.IntProperty(name = "Twist",
        description = "Twist what vertices are connected to each other",
        default = 0)

    @classmethod
    def poll(cls, context):
        ob = context.active_object
        return (ob and ob.type == 'MESH' and context.mode == 'EDIT_MESH')

    def draw(self, context):
        layout = self.layout
        #layout.prop(self, "mode") # no cases yet where 'basic' mode is needed

        # top row
        col_top = layout.column(align=True)
        row = col_top.row(align=True)
        col_left = row.column(align=True)
        col_right = row.column(align=True)
        col_right.active = self.segments != 1
        col_left.prop(self, "segments")
        col_right.prop(self, "min_width", text="")
        # bottom row
        bottom_left = col_left.row()
        bottom_left.active = self.segments != 1
        bottom_left.prop(self, "interpolation", text="")
        bottom_right = col_right.row()
        bottom_right.active = self.interpolation == 'cubic'
        bottom_right.prop(self, "cubic_strength")
        # boolean properties
        col_top.prop(self, "remove_faces")
        if self.loft:
            col_top.prop(self, "loft_loop")

        # override properties
        col_top.separator()
        row = layout.row(align = True)
        row.prop(self, "twist")
        row.prop(self, "reverse")

    def invoke(self, context, event):
        # load custom settings
        context.window_manager.looptools.bridge_loft = self.loft
        settings_load(self)
        return self.execute(context)

    def execute(self, context):
        # initialise
        global_undo, object, bm = initialise()
        edge_faces, edgekey_to_edge, old_selected_faces, smooth = \
            bridge_initialise(bm, self.interpolation)
        settings_write(self)

        # check cache to see if we can save time
        input_method = bridge_input_method(self.loft, self.loft_loop)
        cached, single_loops, loops, derived, mapping = cache_read("Bridge",
            object, bm, input_method, False)
        if not cached:
            # get loops
            loops = bridge_get_input(bm)
            if loops:
                # reorder loops if there are more than 2
                if len(loops) > 2:
                    if self.loft:
                        loops = bridge_sort_loops(bm, loops, self.loft_loop)
                    else:
                        loops = bridge_match_loops(bm, loops)

        # saving cache for faster execution next time
        if not cached:
            cache_write("Bridge", object, bm, input_method, False, False,
                loops, False, False)

        if loops:
            # calculate new geometry
            vertices = []
            faces = []
            max_vert_index = len(bm.verts)-1
            for i in range(1, len(loops)):
                if not self.loft and i%2 == 0:
                    continue
                lines = bridge_calculate_lines(bm, loops[i-1:i+1],
                    self.mode, self.twist, self.reverse)
                vertex_normals = bridge_calculate_virtual_vertex_normals(bm,
                    lines, loops[i-1:i+1], edge_faces, edgekey_to_edge)
                segments = bridge_calculate_segments(bm, lines,
                    loops[i-1:i+1], self.segments)
                new_verts, new_faces, max_vert_index = \
                    bridge_calculate_geometry(bm, lines, vertex_normals,
                    segments, self.interpolation, self.cubic_strength,
                    self.min_width, max_vert_index)
                if new_verts:
                    vertices += new_verts
                if new_faces:
                    faces += new_faces
            # make sure faces in loops that aren't used, aren't removed
            if self.remove_faces and old_selected_faces:
                bridge_save_unused_faces(bm, old_selected_faces, loops)
            # create vertices
            if vertices:
                bridge_create_vertices(bm, vertices)
            # create faces
            if faces:
                new_faces = bridge_create_faces(object, bm, faces, self.twist)
                old_selected_faces = [i for i, face in enumerate(bm.faces) \
                    if face.index in old_selected_faces] # updating list
                bridge_select_new_faces(new_faces, smooth)
            # edge-data could have changed, can't use cache next run
            if faces and not vertices:
                cache_delete("Bridge")
            # delete internal faces
            if self.remove_faces and old_selected_faces:
                bridge_remove_internal_faces(bm, old_selected_faces)
            # make sure normals are facing outside
            bmesh.update_edit_mesh(object.data, tessface=False,
                destructive=True)
            bpy.ops.mesh.normals_make_consistent()

        # cleaning up
        terminate(global_undo)

        return{'FINISHED'}


# circle operator
class Circle(bpy.types.Operator):
    bl_idname = "mesh.looptools_circle"
    bl_label = "Circle"
    bl_description = "Move selected vertices into a circle shape"
    bl_options = {'REGISTER', 'UNDO'}

    custom_radius = bpy.props.BoolProperty(name = "Radius",
        description = "Force a custom radius",
        default = False)
    fit = bpy.props.EnumProperty(name = "Method",
        items = (("best", "Best fit", "Non-linear least squares"),
            ("inside", "Fit inside","Only move vertices towards the center")),
        description = "Method used for fitting a circle to the vertices",
        default = 'best')
    flatten = bpy.props.BoolProperty(name = "Flatten",
        description = "Flatten the circle, instead of projecting it on the " \
            "mesh",
        default = True)
    influence = bpy.props.FloatProperty(name = "Influence",
        description = "Force of the tool",
        default = 100.0,
        min = 0.0,
        max = 100.0,
        precision = 1,
        subtype = 'PERCENTAGE')
    lock_x = bpy.props.BoolProperty(name = "Lock X",
        description = "Lock editing of the x-coordinate",
        default = False)
    lock_y = bpy.props.BoolProperty(name = "Lock Y",
        description = "Lock editing of the y-coordinate",
        default = False)
    lock_z = bpy.props.BoolProperty(name = "Lock Z",
        description = "Lock editing of the z-coordinate",
        default = False)
    radius = bpy.props.FloatProperty(name = "Radius",
        description = "Custom radius for circle",
        default = 1.0,
        min = 0.0,
        soft_max = 1000.0)
    regular = bpy.props.BoolProperty(name = "Regular",
        description = "Distribute vertices at constant distances along the " \
            "circle",
        default = True)

    @classmethod
    def poll(cls, context):
        ob = context.active_object
        return(ob and ob.type == 'MESH' and context.mode == 'EDIT_MESH')

    def draw(self, context):
        layout = self.layout
        col = layout.column()

        col.prop(self, "fit")
        col.separator()

        col.prop(self, "flatten")
        row = col.row(align=True)
        row.prop(self, "custom_radius")
        row_right = row.row(align=True)
        row_right.active = self.custom_radius
        row_right.prop(self, "radius", text="")
        col.prop(self, "regular")
        col.separator()

        col_move = col.column(align=True)
        row = col_move.row(align=True)
        if self.lock_x:
            row.prop(self, "lock_x", text = "X", icon='LOCKED')
        else:
            row.prop(self, "lock_x", text = "X", icon='UNLOCKED')
        if self.lock_y:
            row.prop(self, "lock_y", text = "Y", icon='LOCKED')
        else:
            row.prop(self, "lock_y", text = "Y", icon='UNLOCKED')
        if self.lock_z:
            row.prop(self, "lock_z", text = "Z", icon='LOCKED')
        else:
            row.prop(self, "lock_z", text = "Z", icon='UNLOCKED')
        col_move.prop(self, "influence")

    def invoke(self, context, event):
        # load custom settings
        settings_load(self)
        return self.execute(context)

    def execute(self, context):
        # initialise
        global_undo, object, bm = initialise()
        settings_write(self)
        # check cache to see if we can save time
        cached, single_loops, loops, derived, mapping = cache_read("Circle",
            object, bm, False, False)
        if cached:
            derived, bm_mod = get_derived_bmesh(object, bm, context.scene)
        else:
            # find loops
            derived, bm_mod, single_vertices, single_loops, loops = \
                circle_get_input(object, bm, context.scene)
            mapping = get_mapping(derived, bm, bm_mod, single_vertices,
                False, loops)
            single_loops, loops = circle_check_loops(single_loops, loops,
                mapping, bm_mod)

        # saving cache for faster execution next time
        if not cached:
            cache_write("Circle", object, bm, False, False, single_loops,
                loops, derived, mapping)

        move = []
        for i, loop in enumerate(loops):
            # best fitting flat plane
            com, normal = calculate_plane(bm_mod, loop)
            # if circular, shift loop so we get a good starting vertex
            if loop[1]:
                loop = circle_shift_loop(bm_mod, loop, com)
            # flatten vertices on plane
            locs_2d, p, q = circle_3d_to_2d(bm_mod, loop, com, normal)
            # calculate circle
            if self.fit == 'best':
                x0, y0, r = circle_calculate_best_fit(locs_2d)
            else: # self.fit == 'inside'
                x0, y0, r = circle_calculate_min_fit(locs_2d)
            # radius override
            if self.custom_radius:
                r = self.radius / p.length
            # calculate positions on circle
            if self.regular:
                new_locs_2d = circle_project_regular(locs_2d[:], x0, y0, r)
            else:
                new_locs_2d = circle_project_non_regular(locs_2d[:], x0, y0, r)
            # take influence into account
            locs_2d = circle_influence_locs(locs_2d, new_locs_2d,
                self.influence)
            # calculate 3d positions of the created 2d input
            move.append(circle_calculate_verts(self.flatten, bm_mod,
                locs_2d, com, p, q, normal))
            # flatten single input vertices on plane defined by loop
            if self.flatten and single_loops:
                move.append(circle_flatten_singles(bm_mod, com, p, q,
                    normal, single_loops[i]))

        # move vertices to new locations
        if self.lock_x or self.lock_y or self.lock_z:
            lock = [self.lock_x, self.lock_y, self.lock_z]
        else:
            lock = False
        move_verts(object, bm, mapping, move, lock, -1)

        # cleaning up
        if derived:
            bm_mod.free()
        terminate(global_undo)

        return{'FINISHED'}


# curve operator
class Curve(bpy.types.Operator):
    bl_idname = "mesh.looptools_curve"
    bl_label = "Curve"
    bl_description = "Turn a loop into a smooth curve"
    bl_options = {'REGISTER', 'UNDO'}

    boundaries = bpy.props.BoolProperty(name = "Boundaries",
        description = "Limit the tool to work within the boundaries of the "\
            "selected vertices",
        default = False)
    influence = bpy.props.FloatProperty(name = "Influence",
        description = "Force of the tool",
        default = 100.0,
        min = 0.0,
        max = 100.0,
        precision = 1,
        subtype = 'PERCENTAGE')
    interpolation = bpy.props.EnumProperty(name = "Interpolation",
        items = (("cubic", "Cubic", "Natural cubic spline, smooth results"),
            ("linear", "Linear", "Simple and fast linear algorithm")),
        description = "Algorithm used for interpolation",
        default = 'cubic')
    lock_x = bpy.props.BoolProperty(name = "Lock X",
        description = "Lock editing of the x-coordinate",
        default = False)
    lock_y = bpy.props.BoolProperty(name = "Lock Y",
        description = "Lock editing of the y-coordinate",
        default = False)
    lock_z = bpy.props.BoolProperty(name = "Lock Z",
        description = "Lock editing of the z-coordinate",
        default = False)
    regular = bpy.props.BoolProperty(name = "Regular",
        description = "Distribute vertices at constant distances along the" \
            "curve",
        default = True)
    restriction = bpy.props.EnumProperty(name = "Restriction",
        items = (("none", "None", "No restrictions on vertex movement"),
            ("extrude", "Extrude only","Only allow extrusions (no "\
                "indentations)"),
            ("indent", "Indent only", "Only allow indentation (no "\
                "extrusions)")),
        description = "Restrictions on how the vertices can be moved",
        default = 'none')

    @classmethod
    def poll(cls, context):
        ob = context.active_object
        return(ob and ob.type == 'MESH' and context.mode == 'EDIT_MESH')

    def draw(self, context):
        layout = self.layout
        col = layout.column()

        col.prop(self, "interpolation")
        col.prop(self, "restriction")
        col.prop(self, "boundaries")
        col.prop(self, "regular")
        col.separator()

        col_move = col.column(align=True)
        row = col_move.row(align=True)
        if self.lock_x:
            row.prop(self, "lock_x", text = "X", icon='LOCKED')
        else:
            row.prop(self, "lock_x", text = "X", icon='UNLOCKED')
        if self.lock_y:
            row.prop(self, "lock_y", text = "Y", icon='LOCKED')
        else:
            row.prop(self, "lock_y", text = "Y", icon='UNLOCKED')
        if self.lock_z:
            row.prop(self, "lock_z", text = "Z", icon='LOCKED')
        else:
            row.prop(self, "lock_z", text = "Z", icon='UNLOCKED')
        col_move.prop(self, "influence")

    def invoke(self, context, event):
        # load custom settings
        settings_load(self)
        return self.execute(context)

    def execute(self, context):
        # initialise
        global_undo, object, bm = initialise()
        settings_write(self)
        # check cache to see if we can save time
        cached, single_loops, loops, derived, mapping = cache_read("Curve",
            object, bm, False, self.boundaries)
        if cached:
            derived, bm_mod = get_derived_bmesh(object, bm, context.scene)
        else:
            # find loops
            derived, bm_mod, loops = curve_get_input(object, bm,
                self.boundaries, context.scene)
            mapping = get_mapping(derived, bm, bm_mod, False, True, loops)
            loops = check_loops(loops, mapping, bm_mod)
        verts_selected = [v.index for v in bm_mod.verts if v.select \
            and not v.hide]

        # saving cache for faster execution next time
        if not cached:
            cache_write("Curve", object, bm, False, self.boundaries, False,
                loops, derived, mapping)

        move = []
        for loop in loops:
            knots, points = curve_calculate_knots(loop, verts_selected)
            pknots = curve_project_knots(bm_mod, verts_selected, knots,
                points, loop[1])
            tknots, tpoints = curve_calculate_t(bm_mod, knots, points,
                pknots, self.regular, loop[1])
            splines = calculate_splines(self.interpolation, bm_mod,
                tknots, knots)
            move.append(curve_calculate_vertices(bm_mod, knots, tknots,
                points, tpoints, splines, self.interpolation,
                self.restriction))

        # move vertices to new locations
        if self.lock_x or self.lock_y or self.lock_z:
            lock = [self.lock_x, self.lock_y, self.lock_z]
        else:
            lock = False
        move_verts(object, bm, mapping, move, lock, self.influence)

        # cleaning up
        if derived:
            bm_mod.free()
        terminate(global_undo)

        return{'FINISHED'}


# flatten operator
class Flatten(bpy.types.Operator):
    bl_idname = "mesh.looptools_flatten"
    bl_label = "Flatten"
    bl_description = "Flatten vertices on a best-fitting plane"
    bl_options = {'REGISTER', 'UNDO'}

    influence = bpy.props.FloatProperty(name = "Influence",
        description = "Force of the tool",
        default = 100.0,
        min = 0.0,
        max = 100.0,
        precision = 1,
        subtype = 'PERCENTAGE')
    lock_x = bpy.props.BoolProperty(name = "Lock X",
        description = "Lock editing of the x-coordinate",
        default = False)
    lock_y = bpy.props.BoolProperty(name = "Lock Y",
        description = "Lock editing of the y-coordinate",
        default = False)
    lock_z = bpy.props.BoolProperty(name = "Lock Z",
        description = "Lock editing of the z-coordinate",
        default = False)
    plane = bpy.props.EnumProperty(name = "Plane",
        items = (("best_fit", "Best fit", "Calculate a best fitting plane"),
            ("normal", "Normal", "Derive plane from averaging vertex "\
            "normals"),
            ("view", "View", "Flatten on a plane perpendicular to the "\
            "viewing angle")),
        description = "Plane on which vertices are flattened",
        default = 'best_fit')
    restriction = bpy.props.EnumProperty(name = "Restriction",
        items = (("none", "None", "No restrictions on vertex movement"),
            ("bounding_box", "Bounding box", "Vertices are restricted to "\
            "movement inside the bounding box of the selection")),
        description = "Restrictions on how the vertices can be moved",
        default = 'none')

    @classmethod
    def poll(cls, context):
        ob = context.active_object
        return(ob and ob.type == 'MESH' and context.mode == 'EDIT_MESH')

    def draw(self, context):
        layout = self.layout
        col = layout.column()

        col.prop(self, "plane")
        #col.prop(self, "restriction")
        col.separator()

        col_move = col.column(align=True)
        row = col_move.row(align=True)
        if self.lock_x:
            row.prop(self, "lock_x", text = "X", icon='LOCKED')
        else:
            row.prop(self, "lock_x", text = "X", icon='UNLOCKED')
        if self.lock_y:
            row.prop(self, "lock_y", text = "Y", icon='LOCKED')
        else:
            row.prop(self, "lock_y", text = "Y", icon='UNLOCKED')
        if self.lock_z:
            row.prop(self, "lock_z", text = "Z", icon='LOCKED')
        else:
            row.prop(self, "lock_z", text = "Z", icon='UNLOCKED')
        col_move.prop(self, "influence")

    def invoke(self, context, event):
        # load custom settings
        settings_load(self)
        return self.execute(context)

    def execute(self, context):
        # initialise
        global_undo, object, bm = initialise()
        settings_write(self)
        # check cache to see if we can save time
        cached, single_loops, loops, derived, mapping = cache_read("Flatten",
            object, bm, False, False)
        if not cached:
            # order input into virtual loops
            loops = flatten_get_input(bm)
            loops = check_loops(loops, mapping, bm)

        # saving cache for faster execution next time
        if not cached:
            cache_write("Flatten", object, bm, False, False, False, loops,
                False, False)

        move = []
        for loop in loops:
            # calculate plane and position of vertices on them
            com, normal = calculate_plane(bm, loop, method=self.plane,
                object=object)
            to_move = flatten_project(bm, loop, com, normal)
            if self.restriction == 'none':
                move.append(to_move)
            else:
                move.append(to_move)

        # move vertices to new locations
        if self.lock_x or self.lock_y or self.lock_z:
            lock = [self.lock_x, self.lock_y, self.lock_z]
        else:
            lock = False
        move_verts(object, bm, False, move, lock, self.influence)

        # cleaning up
        terminate(global_undo)

        return{'FINISHED'}


# gstretch operator
class GStretch(bpy.types.Operator):
    bl_idname = "mesh.looptools_gstretch"
    bl_label = "Gstretch"
    bl_description = "Stretch selected vertices to Grease Pencil stroke"
    bl_options = {'REGISTER', 'UNDO'}

    conversion = bpy.props.EnumProperty(name = "Conversion",
        items = (("distance", "Distance", "Set the distance between vertices "\
            "of the converted grease pencil stroke"),
            ("limit_vertices", "Limit vertices", "Set the minimum and maximum "\
            "number of vertices that converted GP strokes will have"),
            ("vertices", "Exact vertices", "Set the exact number of vertices "\
            "that converted grease pencil strokes will have. Short strokes "\
            "with few points may contain less vertices than this number."),
            ("none", "No simplification", "Convert each grease pencil point "\
            "to a vertex")),
        description = "If grease pencil strokes are converted to geometry, "\
            "use this simplification method",
        default = 'limit_vertices')
    conversion_distance = bpy.props.FloatProperty(name = "Distance",
        description = "Absolute distance between vertices along the converted "\
            "grease pencil stroke",
        default = 0.1,
        min = 0.000001,
        soft_min = 0.01,
        soft_max = 100)
    conversion_max = bpy.props.IntProperty(name = "Max Vertices",
        description = "Maximum number of vertices grease pencil strokes will "\
            "have, when they are converted to geomtery",
        default = 32,
        min = 3,
        soft_max = 500,
        update = gstretch_update_min)
    conversion_min = bpy.props.IntProperty(name = "Min Vertices",
        description = "Minimum number of vertices grease pencil strokes will "\
            "have, when they are converted to geomtery",
        default = 8,
        min = 3,
        soft_max = 500,
        update = gstretch_update_max)
    conversion_vertices = bpy.props.IntProperty(name = "Vertices",
        description = "Number of vertices grease pencil strokes will "\
            "have, when they are converted to geometry. If strokes have less "\
            "points than required, the 'Spread evenly' method is used",
        default = 32,
        min = 3,
        soft_max = 500)
    delete_strokes = bpy.props.BoolProperty(name="Delete strokes",
        description = "Remove Grease Pencil strokes if they have been used "\
            "for Gstretch. WARNING: DOES NOT SUPPORT UNDO",
        default = False)
    influence = bpy.props.FloatProperty(name = "Influence",
        description = "Force of the tool",
        default = 100.0,
        min = 0.0,
        max = 100.0,
        precision = 1,
        subtype = 'PERCENTAGE')
    lock_x = bpy.props.BoolProperty(name = "Lock X",
        description = "Lock editing of the x-coordinate",
        default = False)
    lock_y = bpy.props.BoolProperty(name = "Lock Y",
        description = "Lock editing of the y-coordinate",
        default = False)
    lock_z = bpy.props.BoolProperty(name = "Lock Z",
        description = "Lock editing of the z-coordinate",
        default = False)
    method = bpy.props.EnumProperty(name = "Method",
        items = (("project", "Project", "Project vertices onto the stroke, "\
            "using vertex normals and connected edges"),
            ("irregular", "Spread", "Distribute vertices along the full "\
            "stroke, retaining relative distances between the vertices"),
            ("regular", "Spread evenly", "Distribute vertices at regular "\
            "distances along the full stroke")),
        description = "Method of distributing the vertices over the Grease "\
            "Pencil stroke",
        default = 'regular')

    @classmethod
    def poll(cls, context):
        ob = context.active_object
        return(ob and ob.type == 'MESH' and context.mode == 'EDIT_MESH')

    def draw(self, context):
        layout = self.layout
        col = layout.column()

        col.prop(self, "method")
        col.prop(self, "delete_strokes")
        col.separator()

        col_conv = col.column(align=True)
        col_conv.prop(self, "conversion", text="")
        if self.conversion == 'distance':
            col_conv.prop(self, "conversion_distance")
        elif self.conversion == 'limit_vertices':
            row = col_conv.row(align=True)
            row.prop(self, "conversion_min", text="Min")
            row.prop(self, "conversion_max", text="Max")
        elif self.conversion == 'vertices':
            col_conv.prop(self, "conversion_vertices")
        col.separator()

        col_move = col.column(align=True)
        row = col_move.row(align=True)
        if self.lock_x:
            row.prop(self, "lock_x", text = "X", icon='LOCKED')
        else:
            row.prop(self, "lock_x", text = "X", icon='UNLOCKED')
        if self.lock_y:
            row.prop(self, "lock_y", text = "Y", icon='LOCKED')
        else:
            row.prop(self, "lock_y", text = "Y", icon='UNLOCKED')
        if self.lock_z:
            row.prop(self, "lock_z", text = "Z", icon='LOCKED')
        else:
            row.prop(self, "lock_z", text = "Z", icon='UNLOCKED')
        col_move.prop(self, "influence")

    def invoke(self, context, event):
        # flush cached strokes
        if 'Gstretch' in looptools_cache:
            looptools_cache['Gstretch']['single_loops'] = []
        # load custom settings
        settings_load(self)
        return self.execute(context)

    def execute(self, context):
        # initialise
        global_undo, object, bm = initialise()
        settings_write(self)

        # check cache to see if we can save time
        cached, safe_strokes, loops, derived, mapping = cache_read("Gstretch",
            object, bm, False, False)
        if cached:
            straightening = False
            if safe_strokes:
                strokes = gstretch_safe_to_true_strokes(safe_strokes)
            # cached strokes were flushed (see operator's invoke function)
            elif get_grease_pencil(object, context):
                strokes = gstretch_get_strokes(object, context)
            else:
                # straightening function (no GP) -> loops ignore modifiers
                straightening = True
                derived = False
                bm_mod = bm.copy()
                bm_mod.verts.ensure_lookup_table() ### 2.73
                bm_mod.edges.ensure_lookup_table() ### 2.73
                bm_mod.faces.ensure_lookup_table() ### 2.73
                strokes = gstretch_get_fake_strokes(object, bm_mod, loops)
            if not straightening:
                derived, bm_mod = get_derived_bmesh(object, bm, context.scene)
        else:
            # get loops and strokes
            if get_grease_pencil(object, context):
                 # find loops
                derived, bm_mod, loops = get_connected_input(object, bm,
                context.scene, input='selected')
                mapping = get_mapping(derived, bm, bm_mod, False, False, loops)
                loops = check_loops(loops, mapping, bm_mod)
                # get strokes
                strokes = gstretch_get_strokes(object, context)
            else:
                # straightening function (no GP) -> loops ignore modifiers
                derived = False
                mapping = False
                bm_mod = bm.copy()
                bm_mod.verts.ensure_lookup_table() ### 2.73
                bm_mod.edges.ensure_lookup_table() ### 2.73
                bm_mod.faces.ensure_lookup_table() ### 2.73
                edge_keys = [edgekey(edge) for edge in bm_mod.edges if \
                    edge.select and not edge.hide]
                loops = get_connected_selections(edge_keys)
                loops = check_loops(loops, mapping, bm_mod)
                # create fake strokes
                strokes = gstretch_get_fake_strokes(object, bm_mod, loops)

        # saving cache for faster execution next time
        if not cached:
            if strokes:
                safe_strokes = gstretch_true_to_safe_strokes(strokes)
            else:
                safe_strokes = []
            cache_write("Gstretch", object, bm, False, False,
                safe_strokes, loops, derived, mapping)

        # pair loops and strokes
        ls_pairs = gstretch_match_loops_strokes(loops, strokes, object, bm_mod)
        ls_pairs = gstretch_align_pairs(ls_pairs, object, bm_mod, self.method)

        move = []
        if not loops:
            # no selected geometry, convert GP to verts
            if strokes:
                move.append(gstretch_create_verts(object, bm, strokes,
                    self.method, self.conversion, self.conversion_distance,
                    self.conversion_max, self.conversion_min,
                    self.conversion_vertices))
                for stroke in strokes:
                    gstretch_erase_stroke(stroke, context)
        elif ls_pairs:
            for (loop, stroke) in ls_pairs:
                move.append(gstretch_calculate_verts(loop, stroke, object,
                    bm_mod, self.method))
                if self.delete_strokes:
                    if type(stroke) != bpy.types.GPencilStroke:
                        # in case of cached fake stroke, get the real one
                        if get_grease_pencil(object, context):
                            strokes = gstretch_get_strokes(object, context)
                            if loops and strokes:
                                ls_pairs = gstretch_match_loops_strokes(loops,
                                    strokes, object, bm_mod)
                                ls_pairs = gstretch_align_pairs(ls_pairs,
                                    object, bm_mod, self.method)
                                for (l, s) in ls_pairs:
                                    if l == loop:
                                        stroke = s
                                        break
                    gstretch_erase_stroke(stroke, context)

        # move vertices to new locations
        if self.lock_x or self.lock_y or self.lock_z:
            lock = [self.lock_x, self.lock_y, self.lock_z]
        else:
            lock = False
        bmesh.update_edit_mesh(object.data, tessface=True, destructive=True)
        move_verts(object, bm, mapping, move, lock, self.influence)

        # cleaning up
        if derived:
            bm_mod.free()
        terminate(global_undo)

        return{'FINISHED'}


# relax operator
class Relax(bpy.types.Operator):
    bl_idname = "mesh.looptools_relax"
    bl_label = "Relax"
    bl_description = "Relax the loop, so it is smoother"
    bl_options = {'REGISTER', 'UNDO'}

    input = bpy.props.EnumProperty(name = "Input",
        items = (("all", "Parallel (all)", "Also use non-selected "\
                "parallel loops as input"),
            ("selected", "Selection","Only use selected vertices as input")),
        description = "Loops that are relaxed",
        default = 'selected')
    interpolation = bpy.props.EnumProperty(name = "Interpolation",
        items = (("cubic", "Cubic", "Natural cubic spline, smooth results"),
            ("linear", "Linear", "Simple and fast linear algorithm")),
        description = "Algorithm used for interpolation",
        default = 'cubic')
    iterations = bpy.props.EnumProperty(name = "Iterations",
        items = (("1", "1", "One"),
            ("3", "3", "Three"),
            ("5", "5", "Five"),
            ("10", "10", "Ten"),
            ("25", "25", "Twenty-five")),
        description = "Number of times the loop is relaxed",
        default = "1")
    regular = bpy.props.BoolProperty(name = "Regular",
        description = "Distribute vertices at constant distances along the" \
            "loop",
        default = True)

    @classmethod