op_select_islands_flipped.py

import bpy
import bmesh
import operator
from mathutils import Vector
from collections import defaultdict
from math import pi

from . import utilities_uv
import imp
imp.reload(utilities_uv)

class op(bpy.types.Operator):
    bl_idname = "uv.textools_select_islands_flipped"
    bl_label = "Select Flipped"
    bl_description = "Select all flipped UV islands"
    bl_options = {'REGISTER', 'UNDO'}

    @classmethod
    def poll(cls, context):
        if not bpy.context.active_object:
            return False

        if bpy.context.active_object.type != 'MESH':
            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

        #Not in Synced mode
        if bpy.context.scene.tool_settings.use_uv_select_sync:
            return False
            
        return True


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



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

    bpy.context.scene.tool_settings.uv_select_mode = 'FACE'
    bpy.ops.uv.select_all(action='SELECT')

    islands = utilities_uv.getSelectionIslands()
    

    bpy.context.scene.tool_settings.uv_select_mode = 'FACE'
    bpy.context.scene.tool_settings.use_uv_select_sync = False
    bpy.ops.uv.select_all(action='DESELECT')


    for island in islands:

        is_flipped = False
        for face in island:
            if is_flipped:
                break

            # Using 'Sum of Edges' to detect counter clockwise https://stackoverflow.com/questions/1165647/how-to-determine-if-a-list-of-polygon-points-are-in-clockwise-order
            sum = 0
            count = len(face.loops)
            for i in range(count):
                uv_A = face.loops[i][uv_layers].uv
                uv_B = face.loops[(i+1)%count][uv_layers].uv
                sum += (uv_B.x - uv_A.x) * (uv_B.y + uv_A.y)

            if sum > 0:
                # Flipped
                is_flipped = True
                break

        # Select Island if flipped
        if is_flipped:
            for face in island:
                for loop in face.loops:
                    loop[uv_layers].select = True




class Island_bounds:
    faces = []
    center = Vector([0,0])
    min = Vector([0,0])
    max = Vector([0,0])

    def __init__(self, faces):
        bm = bmesh.from_edit_mesh(bpy.context.active_object.data);
        uv_layers = bm.loops.layers.uv.verify();
        
        # Collect topology stats
        self.faces = faces

        #Select Island
        bpy.ops.uv.select_all(action='DESELECT')
        utilities_uv.set_selected_faces(faces)

        bounds = utilities_uv.getSelectionBBox()
        self.center = bounds['center']
        self.min = bounds['min']
        self.max = bounds['max']


        
    def isEqual(A, B):

        # Bounding Box AABB intersection?
        min_x = max(A.min.x, B.min.x)
        min_y = max(A.min.y, B.min.y)
        max_x = min(A.max.x, B.max.x)
        max_y = min(A.max.y, B.max.y)
        if not (max_x < min_x or max_y < min_y):
            return True
        

        return False

bpy.utils.register_class(op)