Blender-TexTools/op_island_mirror.py

import bpy
import os
import bmesh
import math
import operator
from mathutils import Vector
from collections import defaultdict
from itertools import chain # 'flattens' collection of iterables

from . import utilities_uv



class op(bpy.types.Operator):
    bl_idname = "uv.textools_island_mirror"
    bl_label = "Symmetry"
    bl_description = "Mirrors selected faces to other half or averages based on selected edge center"
    bl_options = {'REGISTER', 'UNDO'}
    
    is_stack : bpy.props.BoolProperty(description="Stack the halves on top of each other?", default=False)

    @classmethod
    def poll(cls, context):


        if not bpy.context.active_object:
            return False

        #Only in Edit mode
        if bpy.context.active_object.mode != 'EDIT':
            return False

        #Only in UV editor mode
        if bpy.context.area.type != 'IMAGE_EDITOR':
            return False

        #Requires UV map
        if not bpy.context.object.data.uv_layers:
            return False


        if bpy.context.scene.tool_settings.use_uv_select_sync:
            return False


        if bpy.context.scene.tool_settings.uv_select_mode != 'EDGE' and bpy.context.scene.tool_settings.uv_select_mode != 'FACE':
             return False

        # if bpy.context.scene.tool_settings.use_uv_select_sync:
        #     return False

        return True

    def execute(self, context):
        main(context)
        return {'FINISHED'}



def main(context):
    print("--------------------------- Executing operator_mirror")

    #Store selection
    utilities_uv.selection_store()

    bm = bmesh.from_edit_mesh(bpy.context.active_object.data)
    uv_layers = bm.loops.layers.uv.verify()

    if bpy.context.scene.tool_settings.uv_select_mode == 'EDGE':


        # 1.) Collect left and right side verts
        verts_middle = [];

        for face in bm.faces:
            if face.select:
                for loop in face.loops:
                    if loop[uv_layers].select and loop.vert not in verts_middle:
                        verts_middle.append(loop.vert)
                    
        # 2.) Align UV shell
        alignToCenterLine()

        # Convert to Vert selection and extend edge loop in 3D space
        bpy.ops.mesh.select_mode(use_extend=False, use_expand=False, type='VERT')
        bpy.ops.mesh.select_all(action='DESELECT')
        for vert in verts_middle:
            vert.select = True

        bpy.ops.mesh.select_mode(use_extend=True, use_expand=False, type='EDGE')
        bpy.ops.mesh.loop_multi_select(ring=False)
        for vert in bm.verts:
            if vert.select and vert not in verts_middle:
                print("Append extra vert to symmetry line from xyz edge loop")
                verts_middle.append(vert)

        # Select UV shell Again
        bpy.ops.mesh.select_linked(delimit={'UV'})
        verts_island = []
        for vert in bm.verts:
            if vert.select:
                verts_island.append(vert)


        # 3.) Restore UV vert selection
        x_middle = 0
        bpy.ops.uv.select_all(action='DESELECT')
        for face in bm.faces:
            if face.select:
                for loop in face.loops:
                    if loop.vert in verts_middle:
                        loop[uv_layers].select = True
                        x_middle = loop[uv_layers].uv.x;


        print("Middle "+str(len(verts_middle))+"x, x pos: "+str(x_middle))

        # Extend selection
        bpy.ops.uv.select_more()
        verts_A = [];
        verts_B = [];
        for face in bm.faces:
            if face.select:
                for loop in face.loops:
                    if loop[uv_layers].select and loop.vert not in verts_middle:
                        if loop[uv_layers].uv.x <= x_middle:
                            # Left
                            if loop.vert not in verts_A:
                                verts_A.append(loop.vert)

                        elif loop[uv_layers].uv.x > x_middle:
                            # Right
                            if loop.vert not in verts_B:
                                verts_B.append(loop.vert)

        

        
        def remove_doubles():
            verts_double = [vert for vert in verts_island if (vert in verts_A and vert in verts_B)]

            # print("Temp  double: "+str(len(verts_double))+"x")
            if len(verts_double) > 0:
                print("TODO: Remove doubles "+str(len(verts_double)))
                for vert in verts_double:
                    verts_A.remove(vert)
                    verts_B.remove(vert)
                    verts_middle.append(vert)

        def extend_half_selection(verts_middle, verts_half, verts_other):
            # Select initial half selection
            bpy.ops.uv.select_all(action='DESELECT')
            for face in bm.faces:
                if face.select:
                    for loop in face.loops:
                        if loop.vert in verts_half:
                            loop[uv_layers].select = True

            # Extend selection                
            bpy.ops.uv.select_more()

            # count_added = 0
            for face in bm.faces:
                if face.select:
                    for loop in face.loops:
                        if loop.vert not in verts_half and loop.vert not in verts_middle and loop[uv_layers].select:
                            verts_half.append(loop.vert)


        remove_doubles()

        # Limit iteration loops
        max_loops_extend = 200
        for i in range(0, max_loops_extend):
            print("Now extend selection A / B")
            count_hash = str(len(verts_A))+"_"+str(len(verts_B));
            extend_half_selection(verts_middle, verts_A, verts_B)
            extend_half_selection(verts_middle, verts_B, verts_A)
            remove_doubles()

            count_hash_new = str(len(verts_A))+"_"+str(len(verts_B));
            if count_hash_new == count_hash:
                print("Break loop, same as previous loop")
                break;

        print("Edge, Sides: L:"+str(len(verts_A))+" | R:"+str(len(verts_B)))

        # 4.) Mirror Verts
        mirror_verts(verts_middle, verts_A, verts_B, False)


    if bpy.context.scene.tool_settings.uv_select_mode == 'FACE':

        # 1.) Get selected UV faces to vert faces
        selected_faces = []
        for face in bm.faces:
            if face.select:
                # Are all UV faces selected?
                countSelected = 0
                for loop in face.loops:
                    if loop[uv_layers].select:
                        countSelected+=1
                        # print("Vert selected "+str(face.index))
                if countSelected == len(face.loops):
                    selected_faces.append(face)


        # if bpy.context.scene.tool_settings.use_uv_select_sync == False:

        bpy.ops.uv.select_linked()
        verts_all = []
        for face in bm.faces:
            if face.select:
                for loop in face.loops:
                    if(loop.vert not in verts_all):
                        verts_all.append(loop.vert)

        print("Verts shell: "+str(len(verts_all)))


        bpy.ops.mesh.select_all(action='DESELECT')
        for face in selected_faces:
            face.select = True


        # 2.) Select Vert shell's outer edges
        bpy.ops.mesh.select_linked(delimit=set())
        bpy.ops.mesh.select_mode(use_extend=False, use_expand=False, type='EDGE')
        bpy.ops.mesh.region_to_loop()
        edges_outer_shell = [e for e in bm.edges if e.select]

        # 3.) Select Half's outer edges
        bpy.ops.mesh.select_mode(use_extend=False, use_expand=False, type='FACE')
        bpy.ops.mesh.select_all(action='DESELECT')
        for face in selected_faces:
            face.select = True
        bpy.ops.mesh.select_mode(use_extend=False, use_expand=False, type='EDGE')
        bpy.ops.mesh.region_to_loop()
        edges_outer_selected = [e for e in bm.edges if e.select]

        # 4.) Mask edges exclusive to edges_outer_selected (symmetry line)
        edges_middle = [item for item in edges_outer_selected if item not in edges_outer_shell]

        # 5.) Convert to UV selection
        verts_middle = []
        for edge in edges_middle:
            if edge.verts[0] not in verts_middle:
                verts_middle.append(edge.verts[0])
            if edge.verts[1] not in verts_middle:
                verts_middle.append(edge.verts[1])

        #Select all Vert shell faces
        bpy.ops.mesh.select_linked(delimit=set())
        #Select UV matching vert array
        bpy.ops.uv.select_all(action='DESELECT')
        for face in bm.faces:
            if face.select:
                for loop in face.loops:
                    if loop.vert in verts_middle:
                        loop[uv_layers].select = True

        # 5.) Align UV shell
        alignToCenterLine()

        # 7.) Collect left and right side verts
        verts_A = [];
        verts_B = [];

        bpy.ops.uv.select_all(action='DESELECT')
        for face in selected_faces:
            for loop in face.loops:
                if loop.vert not in verts_middle and loop.vert not in verts_A:
                    verts_A.append(loop.vert)

        for vert in verts_all:
            if vert not in verts_middle and vert not in verts_A and vert not in verts_B:
                verts_B.append(vert)

        # 8.) Mirror Verts
        mirror_verts(verts_middle, verts_A, verts_B, True)

    #Restore selection
    # utilities_uv.selection_restore()





def mirror_verts(verts_middle, verts_A, verts_B, isAToB):

    print("--------------------------------\nMirror: C:"+str(len(verts_middle))+" ; verts: "+str(len(verts_A))+"|"+str(len(verts_B))+"x,     A to B? "+str(isAToB))


    bm = bmesh.from_edit_mesh(bpy.context.active_object.data)
    uv_layers = bm.loops.layers.uv.verify()


    # Get verts_island
    verts_island = []
    for vert in verts_middle:
        verts_island.append(vert)
    for vert in verts_A:
        verts_island.append(vert)
    for vert in verts_B:
        verts_island.append(vert)

    # Select Island as Faces
    bpy.ops.mesh.select_mode(use_extend=False, use_expand=False, type='VERT')
    bpy.ops.mesh.select_all(action='DESELECT')
    for vert in verts_island:
        vert.select = True
    bpy.ops.mesh.select_mode(use_extend=False, use_expand=True, type='FACE')

    # Collect Librarys of verts / UV
    vert_to_uv = utilities_uv.get_vert_to_uv(bm, uv_layers)
    uv_to_vert = utilities_uv.get_uv_to_vert(bm, uv_layers)
    uv_to_face = {}
    # UV clusters / groups (within 0.000001 distance)
    clusters = []
    uv_to_clusters = {}
    vert_to_clusters = {}

    for face in bm.faces:
        if face.select:
            for loop in face.loops:
                vert = loop.vert
                uv = loop[uv_layers]

                if uv not in uv_to_face:
                    uv_to_face[ uv ] = face;

                # clusters
                isMerged = False
                for cluster in clusters:
                    d = (uv.uv - cluster.uvs[0].uv).length
                    if d <= 0.0000001:
                        #Merge
                        cluster.append(uv)
                        uv_to_clusters[uv] = cluster
                        if vert not in vert_to_clusters:
                            vert_to_clusters[vert] = cluster
                        isMerged = True;
                        break;
                if not isMerged:
                    #New Group
                    clusters.append( UVCluster(vert, [uv]) )
                    uv_to_clusters[uv] = clusters[-1]
                    if vert not in vert_to_clusters:
                            vert_to_clusters[vert] = clusters[-1]

    # Get Center X
    x_middle = vert_to_uv[ verts_middle[0] ][0].uv.x;
    

    # 3.) Grow layer by layer
    bpy.ops.mesh.select_mode(use_extend=False, use_expand=False, type='VERT')
    bpy.context.scene.tool_settings.uv_select_mode = 'VERTEX'


    clusters_processed = []

    def select_extend_filter(clusters_border, clusters_mask):
        # print("Extend A/B")
        connected_clusters = []
        for cluster in clusters_border:

            # Select and Extend selection
            bpy.ops.uv.select_all(action='DESELECT')
            for uv in cluster.uvs:
                uv.select = True
            bpy.ops.uv.select_more()

            # Collect extended
            uv_extended = [uv for clusterMask in clusters_mask for uv in clusterMask.uvs if (uv.select and clusterMask not in clusters_processed)]
            clusters_extended = []
            for uv in uv_extended:
                if uv_to_clusters[uv] not in clusters_extended:
                    clusters_extended.append( uv_to_clusters[uv] )

            # Sort by distance
            groups_distance = {}
            for i in range(0, len(clusters_extended)):
                sub_group = clusters_extended[i]
                groups_distance[i] = (cluster.uvs[0].uv - sub_group.uvs[0].uv).length
            
            # Append to connected clusters
            array = []
            for item in sorted(groups_distance.items(), key=operator.itemgetter(1)):
                key = item[0]
                clust = clusters_extended[key]
                array.append( clust )
                if clust not in clusters_processed:
                    clusters_processed.append(clust)

            connected_clusters.append( array )
            
            if cluster not in clusters_processed:
                clusters_processed.append( cluster )


            bpy.ops.uv.select_all(action='DESELECT')
            for uv in uv_extended:
                uv.select = True


        return connected_clusters





    
    mask_A = [vert_to_clusters[vert] for vert in verts_A]
    mask_B = [vert_to_clusters[vert] for vert in verts_B]

    border_A = list([vert_to_clusters[vert] for vert in verts_middle])
    border_B = list([vert_to_clusters[vert] for vert in verts_middle])
    
    for step in range(0, 8):

        if len(border_A) == 0:
            print("{}.: Finished scanning with no growth iterations".format(step))
            break;
        if len(border_A) != len(border_B) or len(border_A) == 0:
            print("Abort: non compatible border A/B: {}x {}x ".format(len(border_A), len(border_B)))
            break;

        print("{}.: border {}x|{}x, processed: {}x".format(step, len(border_A), len(border_B), len(clusters_processed)))
        
        # Collect connected pairs for each side
        connected_A = select_extend_filter(border_A, mask_A)
        connected_B = select_extend_filter(border_B, mask_B)

        print("  Connected: {}x|{}x".format(len(connected_A), len(connected_B)))

        border_A.clear()
        border_B.clear()

        # Traverse through pairs
        for i in range(0, min(len(connected_A), len(connected_B)) ):
            if len(connected_A[i]) == 0:
                continue
            if len(connected_A[i]) != len(connected_B[i]):
                print(".    Error: Inconsistent grow mappings from {}  {}x | {}x".format(i, len(connected_A[i]), len(connected_B[i]) ))
                continue

            indexA = [cluster.vertex.index for cluster in connected_A[i] ]
            indexB = [cluster.vertex.index for cluster in connected_B[i] ]
            indexA = str(indexA).replace("[","").replace("]","").replace(" ","")
            indexB = str(indexB).replace("[","").replace("]","").replace(" ","")
            print(".    Map {}|{} = {}x|{}x".format(indexA, indexB, len(connected_A[i]), len(connected_B[i]) ) )



            if True:#isAToB:
                # Copy A side to B
                for cluster in connected_B[i]:
                    for uv in cluster.uvs:
                        pos = connected_A[i][0].uvs[0].uv.copy()
                        pos.x = x_middle - (pos.x-x_middle)# Flip cooreindate
                        # uv.uv = pos
            
            # border_A[i] = uv_to_clusters[ connected_A[i][0] ] 
            # border_B[i] = uv_to_clusters[ connected_B[i][0] ] 
            for j in range(len(connected_A[i])):
                border_A.append( connected_A[i][j] )
                border_B.append( connected_B[i][j] )



            # for uv in clusters_B[idxB]:
        #                     pos = clusters_A[idxA][0].uv.copy()
        #                     # Flip cooreindate
        #                     pos.x = x_middle - (pos.x-x_middle)
        #                     uv.uv = pos

            # for j in range(0, len(connected_A[i])):
            #     # Group A and B
            #     groupA = connected_A[i][j];
            #     groupB = connected_B[i][j];
            #     # vertexA = [vert_to_clusters[key] for key in vert_to_clusters if vert_to_clusters[key] == groupA]
            #     print("...map {} -> {}".format(groupA, groupB))



        # for j in range(0, count):
        #     if len(connected_A[j]) != len(connected_B[j]):
        #         # print("Error: Inconsistent grow mappings from {}:{}x | {}:{}x".format(border_A[j].index,len(connected_A[j]), border_B[j].index, len(connected_B[j]) ))
        #         print("Error: Inconsistent grow mappings from {}  {}x | {}x".format(j, len(connected_A[j]), len(connected_B[j]) ))
        #         continue

        #     for k in range(0, len(connected_A[j])):
        #         # Vertex A and B
        #         vA = connected_A[j][k];
        #         vB = connected_B[j][k];

        #         uvsA = vert_to_uv[vA];
        #         uvsB = vert_to_uv[vB];

        #         clusters_A = collect_clusters(uvsA)
        #         clusters_B = collect_clusters(uvsB)

        #         if len(clusters_A) != len(clusters_B):
        #             print("Error: Inconsistent vertex UV group pairs at vertex {} : {}".format(vA.index, vB.index))
        #             continue


        #         message= "...Map {0} -> {1}  = UVs {2}|{3}x | UV-Groups {4}x|{5}x".format( vA.index, vB.index, len(uvsA), len(uvsB), len(clusters_A), len(clusters_B) )
        #         if len(clusters_A) > 1:
        #             message = ">> "+message
        #         print(message)



        #         if len(clusters_A) > 0:
        #             # For each group

        #             sortA = {}
        #             sortB = {}
        #             for g in range(0, len(clusters_A)):
        #                 uv_A = clusters_A[g][0].uv.copy()
        #                 uv_B = clusters_B[g][0].uv.copy()

        #                 # localize X values (from symmetry line)
        #                 uv_A.x = (uv_A.x - x_middle)
        #                 uv_B.x = (uv_B.x - x_middle)

        #                 sortA[g] = abs(uv_A.x) + uv_A.y*2.0
        #                 sortB[g] = abs(uv_B.x) + uv_B.y*2.0
        #                 # print("    .   [{}] : {:.2f}, {:.2f} | {:.2f}, {:.2f}".format(g, uv_A.x, uv_A.y, uv_B.x, uv_B.y))
        #                 print("    .   [{}] : {:.2f} | {:.2f}".format(g, sortA[g], sortB[g]))

        #             # Sort sortA by value
        #             sortedA = sorted(sortA.items(), key=operator.itemgetter(1))
        #             sortedB = sorted(sortB.items(), key=operator.itemgetter(1))
                    
        #             for g in range(0, len(clusters_A)):
        #                 # sortedA[g]
        #                 idxA = sortedA[g][0]
        #                 idxB = sortedB[g][0]

        #                 print("Map clusters_A {} -> ".format(idxA, idxB))
        #                 for uv in clusters_B[idxB]:
        #                     pos = clusters_A[idxA][0].uv.copy()
        #                     # Flip cooreindate
        #                     pos.x = x_middle - (pos.x-x_middle)
        #                     uv.uv = pos

        #         border_A.append(vA)
        #         border_B.append(vB)



    print("--------------------------------")
    '''

    def select_extend_filter(verts_border, verts_mask):
        # print("Extend A/B")
        connected_verts = []
        for i in range(0, len(verts_border)):
             # Collect connected edge verts
            verts_connected_edges = []
            for edge in verts_border[i].link_edges:
                if(edge.verts[0] not in verts_connected_edges):
                    verts_connected_edges.append(edge.verts[0])
                if(edge.verts[1] not in verts_connected_edges):
                    verts_connected_edges.append(edge.verts[1])

            # Select vert on border
            bpy.ops.mesh.select_all(action='DESELECT')
            verts_border[i].select = True
            

            # Extend selection
            bpy.ops.mesh.select_more()

            # Filter selected verts against mask, connected edges, processed and border
            verts_extended = [vert for vert in bm.verts if (vert.select and vert in verts_connected_edges and vert in verts_mask and vert and vert not in verts_border and vert not in verts_processed)]
            

            # print("    "+str(i)+". scan: "+str(verts_border[i].index)+"; ext: "+str(len(verts_extended))+"x")

            connected_verts.append( [] )

            # Sort by distance
            verts_distance = {}
            for vert in verts_extended:
                verts_distance[vert] = (verts_border[i].co - vert.co).length

            for item in sorted(verts_distance.items(), key=operator.itemgetter(1)):
                connected_verts[i].append( item[0] )

            if verts_border[i] not in verts_processed:
                verts_processed.append(verts_border[i])

        return connected_verts

    # find UV vert blobs , see which ones are same spot
    def collect_clusters(uvs):
        groups = []
        for uv in uvs:
            if len(groups) == 0:
                groups.append([uv])
            else:
                isMerged = False
                for group in groups:
                    d = (uv.uv - group[0].uv).length
                    if d <= 0.0000001:
                        #Merge
                        group.append(uv)
                        isMerged = True;
                        break;
                if not isMerged:
                    #New Group
                    groups.append([uv])
        return groups

    
    border_A = [vert for vert in verts_middle]
    border_B = [vert for vert in verts_middle]
    

    for i in range(0, 200):

        if len(border_A) == 0:
            print("Finished scanning at {} growth iterations".format(i))
            break;
        if len(border_A) != len(border_B) or len(border_A) == 0:
            print("Abort: non compatible border A/B: {}x {}x ".format(len(border_A), len(border_B)))
            break;

        connected_A = select_extend_filter(border_A, verts_A)
        connected_B = select_extend_filter(border_B, verts_B)

        print("Map pairs: {}|{}".format(len(connected_A), len(connected_B)))

        border_A.clear()
        border_B.clear()

        count = min(len(connected_A), len(connected_B))
        for j in range(0, count):
            if len(connected_A[j]) != len(connected_B[j]):
                # print("Error: Inconsistent grow mappings from {}:{}x | {}:{}x".format(border_A[j].index,len(connected_A[j]), border_B[j].index, len(connected_B[j]) ))
                print("Error: Inconsistent grow mappings from {}  {}x | {}x".format(j, len(connected_A[j]), len(connected_B[j]) ))
                continue

            for k in range(0, len(connected_A[j])):
                # Vertex A and B
                vA = connected_A[j][k];
                vB = connected_B[j][k];

                uvsA = vert_to_uv[vA];
                uvsB = vert_to_uv[vB];

                clusters_A = collect_clusters(uvsA)
                clusters_B = collect_clusters(uvsB)

                if len(clusters_A) != len(clusters_B):
                    print("Error: Inconsistent vertex UV group pairs at vertex {} : {}".format(vA.index, vB.index))
                    continue


                message= "...Map {0} -> {1}  = UVs {2}|{3}x | UV-Groups {4}x|{5}x".format( vA.index, vB.index, len(uvsA), len(uvsB), len(clusters_A), len(clusters_B) )
                if len(clusters_A) > 1:
                    message = ">> "+message
                print(message)



                if len(clusters_A) > 0:
                    # For each group


                    
                    sortA = {}
                    sortB = {}
                    for g in range(0, len(clusters_A)):
                        uv_A = clusters_A[g][0].uv.copy()
                        uv_B = clusters_B[g][0].uv.copy()

                        # localize X values (from symmetry line)
                        uv_A.x = (uv_A.x - x_middle)
                        uv_B.x = (uv_B.x - x_middle)

                        sortA[g] = abs(uv_A.x) + uv_A.y*2.0
                        sortB[g] = abs(uv_B.x) + uv_B.y*2.0
                        # print("    .   [{}] : {:.2f}, {:.2f} | {:.2f}, {:.2f}".format(g, uv_A.x, uv_A.y, uv_B.x, uv_B.y))
                        print("    .   [{}] : {:.2f} | {:.2f}".format(g, sortA[g], sortB[g]))

                    # Sort sortA by value
                    sortedA = sorted(sortA.items(), key=operator.itemgetter(1))
                    sortedB = sorted(sortB.items(), key=operator.itemgetter(1))
                    
                    for g in range(0, len(clusters_A)):
                        # sortedA[g]
                        idxA = sortedA[g][0]
                        idxB = sortedB[g][0]

                        print("Map clusters_A {} -> ".format(idxA, idxB))
                        for uv in clusters_B[idxB]:
                            pos = clusters_A[idxA][0].uv.copy()
                            # Flip cooreindate
                            pos.x = x_middle - (pos.x-x_middle)
                            uv.uv = pos
                        
                
                    # print("Sorted: '"+str(sortedA)+"'")
                    # print("Sorted: '"+str(sortedB)+"'")

                    # for item in sorted(verts_distance.items(), key=operator.itemgetter(1)):
                    #     connected_verts[i].append( item[0] )

                    # TODO: Now map groups to each other
                    # uv_avg_A = Vector([0,0])
                    # uv_avg_B = Vector([0,0])
                    # for m in range(0, len(clusters_A)):
                    #     print("        . ")
                    #     uv_avg_A+= clusters_A[m][0].uv;
                    #     uv_avg_B+= clusters_B[m][0].uv;

                    # uv_avg_A/=len(clusters_A)
                    # uv_avg_B/=len(clusters_B)

                    # print("        avg: {} : {}".format(uv_avg_A, uv_avg_B))
            
                # Done processing, add to border arrays
                border_A.append(vA)
                border_B.append(vB)

    '''

def alignToCenterLine():
    print("align to center line")

    bm = bmesh.from_edit_mesh(bpy.context.active_object.data)
    uv_layers = bm.loops.layers.uv.verify()
    bpy.ops.mesh.select_mode(use_extend=False, use_expand=False, type='EDGE')

    # 1.) Get average edges rotation + center
    average_angle = 0
    average_center = Vector((0,0))
    average_count = 0
    for face in bm.faces:
        if face.select:
            verts = []
            for loop in face.loops:
                if loop[uv_layers].select:
                    verts.append(loop[uv_layers].uv)

            if len(verts) == 2:
                diff = verts[1] - verts[0]
                angle = math.atan2(diff.y, diff.x)%(math.pi)
                average_center += verts[0] + diff/2
                average_angle += angle
                average_count+=1

    if average_count >0:
        average_angle/=average_count
        average_center/=average_count

    average_angle-= math.pi/2 #Rotate -90 degrees so aligned horizontally

    # 2.) Rotate UV Shell around edge
    bpy.context.tool_settings.transform_pivot_point = 'CURSOR'
    bpy.ops.uv.cursor_set(location=average_center)

    bpy.ops.uv.select_linked()
    bpy.ops.transform.rotate(value=average_angle, orient_axis='Z', constraint_axis=(False, False, False), orient_type='GLOBAL', mirror=False, use_proportional_edit=False)



class UVCluster:
    uvs = []
    vertex = None
    
    def __init__(self, vertex, uvs):
        self.vertex = vertex
        self.uvs = uvs
    
    def append(self, uv):
        self.uvs.append(uv)

bpy.utils.register_class(op)