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#########################################################################################
#
# This code takes two input objects which, as they are located, generate a mesh containing
# non-manifold elements when Boolean Union is applied. One of the two objects is randomly
# shifted in space within a user-defined threshold for a number of iterations until the
# Boolean Operator returns a valid mesh (without non-manifold elements).
#
#########################################################################################

import bpy
import bmesh
import random
from random import *

# Boolean_check = 0 Non-Manifold Found / boolean_check = 1 Non-Manifold NOT Found

boolean_check = 1

#How many times it tries to adjust the objects' location 
n_attempts = 50

#This parameter depends on the dimension of the 3D objects

scaler = 0.0000008

#The two objects used for Boolean UNION

object_1 = "Name of first object"

object_2 = "Name of second object"

#Move the objects along the 3 directions
boolean_adjustment_x=[]
boolean_adjustment_y=[]
boolean_adjustment_z=[]

#Prepare random shifts along three axis
for index in range (n_attempts):
    
    boolean_adjustment_x.append(scaler*random())
    boolean_adjustment_y.append(scaler*random())
    boolean_adjustment_z.append(scaler*random())

#Space shift adjustment Loop
for bool_index in range (n_attempts):
    
    print('Iteration number ' +str(bool_index))
    
    print ('Shift in x is ' +str(boolean_adjustment_x[bool_index]))
    print ('Shift in y is ' +str(boolean_adjustment_y[bool_index]))
    print ('Shift in z is ' +str(boolean_adjustment_z[bool_index]))
    
    bpy.context.scene.objects.active = bpy.data.objects[bpy.data.objects.find(object_1)]
    
    bpy.data.objects[bpy.data.objects.find(object_1)].select = True
    
    #Temporary copy of first object
    bpy.ops.object.duplicate_move(OBJECT_OT_duplicate={"linked":False, "mode":'TRANSLATION'}, TRANSFORM_OT_translate={"value":(boolean_adjustment_x[bool_index], boolean_adjustment_y[bool_index], boolean_adjustment_z[bool_index]), "constraint_axis":(True, True, True), "constraint_orientation":'GLOBAL', "mirror":False, "proportional":'DISABLED', "proportional_edit_falloff":'SMOOTH', "proportional_size":1, "snap":False, "snap_target":'CLOSEST', "snap_point":(0, 0, 0), "snap_align":False, "snap_normal":(0, 0, 0), "texture_space":False, "release_confirm":False})
    
    #Attempt Boolean UNION between two objects
    bpy.ops.object.modifier_add(type='BOOLEAN')
    
    bpy.data.objects[bpy.data.objects.find(object_1 +'.001')].modifiers[0].operation='UNION'
    
    bpy.data.objects[bpy.data.objects.find(object_1 +'.001')].modifiers[0].object=bpy.data.objects[bpy.data.objects.find(object_2)]
    
    bpy.ops.object.modifier_apply(modifier='Boolean') 
    
    #-----------------------Non-manifold Check-------------------------------------------
    
    bpy.ops.object.mode_set(mode = 'EDIT')
    
    bpy.ops.mesh.select_all( action='DESELECT' )
    
    bpy.ops.mesh.select_non_manifold(extend=True)
    
    obj=bpy.context.object
    
    bm=bmesh.from_edit_mesh(obj.data)
    
    non_manifolds_counter = 0
    
    #Loop through all vertices and check if they have been selected as non-manifold, if so break the loop (unsuccessful Boolean)
    for v in bm.verts:
        if v.select:
            print('Found a manifold!')
            boolean_check = 0
            non_manifolds_counter = non_manifolds_counter + 1
            break
            
    bpy.ops.object.mode_set(mode = 'OBJECT')
    
    #-------------------------Non-manifolds Check END------------------------------------------
    
    #----------------------------------Check the BOOLEAN flag----------------------------------
    
    #End program if there are NOT non-manifold elements, otherwise keep going with a new shift in x y z...
    
    if (boolean_check == 1 ): 
  
        bool_index = n_attempts
        print("Boolean Union successful!")
        break
    
    else:
        
        #Delete the Unioned mesh with non-manifold elements and re-start with new shift in x y z...
        bpy.ops.object.delete(use_global=True)
        
        bpy.ops.object.select_all(action = 'DESELECT')
        
        boolean_check = 1