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Given a mesh with no faces, like so, is there way to return three lists of vertices, where each list contains a sequence of vertices for each separate island of edges in the order they are connected (like a polyline)? For the circle, where there is no start or end, any vertex may be arbitrarily used as the start/end vertex in the list.
With brute force, I can check all edges and see which share a vertex, but is there a smarter way?
Given you are not using face data I would just convert the mesh to curve:
Each spline becomes its own island and has its own start/end points in sequence.
import bpy
obj = bpy.context.object
bpy.ops.object.convert(target='CURVE')
print(f"curve: {obj.name}")
for i, s in enumerate(obj.data.splines):
start_vert = s.points[0].co
end_vert = s.points[-1].co
print(f"spline: {i}")
print(f"start index: 0")
print(f"starts location: {start_vert}")
print(f"end index: {len(s.points)-1}")
print(f"end location: {end_vert}")
providing output:
curve: Circle
spline: 0
start index: 0
starts location: <Vector (3.0000, 0.0000, 0.0000, 0.0000)>
end index: 1
end location: <Vector (3.3874, 0.5697, 0.0000, 0.0000)>
spline: 1
start index: 0
starts location: <Vector (2.0000, 0.0000, 0.0000, 0.0000)>
end index: 4
end location: <Vector (1.9818, 1.0072, 0.0000, 0.0000)>
spline: 2
start index: 0
starts location: <Vector (0.0000, 1.0000, 0.0000, 0.0000)>
end index: 31
end location: <Vector (-0.1951, 0.9808, 0.0000, 0.0000)>
Not sure is there has a convenient function in blender api to do this. But my idea is separate by Loose Parts to single object and for every object duplicated, find the correct order of the vertices. finally delete them and restore the select data.
Suppose the object is:
bpy.ops.mesh.separate(type='LOOSE')
to achieve.
here is the function, it will return the objects are separated.
# Suppose in Object mode, and the object selected
import bpy, bmesh
def separate_obj():
context_obj_old = bpy.context.object
data_objects_old = [obj for obj in bpy.data.objects]
old_selected = bpy.context.selected_objects
for obj in old_selected:
obj.select_set(False)
bpy.context.object.select_set(True)
bpy.ops.object.duplicate()
object_duplicated = bpy.context.object
bpy.ops.object.mode_set(mode = 'EDIT')
obj = bpy.context.object
me = obj.data
bm = bmesh.from_edit_mesh(me)
verts = bm.verts
edges = bm.edges
verts.ensure_lookup_table()
bm.select_mode |= {'VERT'}
bm.select_flush_mode()
# deslect all
for v in verts:
v.select_set(False)
while verts:
# select first vert
verts[0].select_set(True)
bpy.ops.mesh.select_linked(delimit=set())
bmesh.update_edit_mesh(me)
bpy.ops.mesh.separate(type='SELECTED')
verts.ensure_lookup_table()
bpy.ops.object.mode_set(mode = 'OBJECT')
islands = [obj for obj in bpy.data.objects if obj not in data_objects_old and obj != object_duplicated]
for i in islands:
i.select_set(False)
object_duplicated.select_set(True)
bpy.ops.object.delete(use_global=True, confirm=False)
for obj in old_selected:
obj.select_set(True)
bpy.context.view_layer.objects.active = context_obj_old
return islands
islands = separate_obj()
print(islands)
print("")
next step is find the correct order of vertices for every objects
# Suppose in Object mode, and the object selected
import bpy, bmesh
def separate_obj():
context_obj_old = bpy.context.object
data_objects_old = [obj for obj in bpy.data.objects]
old_selected = bpy.context.selected_objects
for obj in old_selected:
obj.select_set(False)
bpy.context.object.select_set(True)
bpy.ops.object.duplicate()
object_duplicated = bpy.context.object
bpy.ops.object.mode_set(mode = 'EDIT')
obj = bpy.context.object
me = obj.data
bm = bmesh.from_edit_mesh(me)
verts = bm.verts
edges = bm.edges
verts.ensure_lookup_table()
bm.select_mode |= {'VERT'}
bm.select_flush_mode()
# deslect all
for v in verts:
v.select_set(False)
while verts:
# select first vert
verts[0].select_set(True)
bpy.ops.mesh.select_linked(delimit=set())
bmesh.update_edit_mesh(me)
bpy.ops.mesh.separate(type='SELECTED')
verts.ensure_lookup_table()
bpy.ops.object.mode_set(mode = 'OBJECT')
islands = [obj for obj in bpy.data.objects if obj not in data_objects_old and obj != object_duplicated]
for i in islands:
i.select_set(False)
object_duplicated.select_set(True)
bpy.ops.object.delete(use_global=True, confirm=False)
for obj in old_selected:
obj.select_set(True)
bpy.context.view_layer.objects.active = context_obj_old
return islands
islands = separate_obj()
print(islands)
print("")
# -- store selected data
context_obj_old = bpy.context.object
old_selected = bpy.context.selected_objects
for obj in old_selected:
obj.select_set(False)
# -- store selected data END
list_coords = []
for obj in islands:
bpy.context.view_layer.objects.active = obj
bpy.ops.object.mode_set(mode = 'EDIT')
me = obj.data
bm = bmesh.from_edit_mesh(me)
verts = bm.verts
edges = bm.edges
verts.ensure_lookup_table()
edges.ensure_lookup_table()
bm.select_mode |= {'VERT'}
bm.select_flush_mode()
# deslect all
for v in verts:
v.select_set(False)
bm.select_mode |= {'EDGE'}
bm.select_flush_mode()
coords = []
first_edge = None
if edges:
for e in edges:
l0 = len(e.verts[0].link_edges)
l1 = len(e.verts[1].link_edges)
if l0 > 2 or l1 > 2:
first_edge = False
break
if l0 == 1 or l1 == 1:
first_edge = e
break
if first_edge is None: # means closed path
first_edge = edges[0]
elif first_edge is False: # complex path
list_coords.append(coords)
bpy.ops.object.mode_set(mode = 'OBJECT')
continue
p1 = first_edge.verts[0]
p2 = first_edge.verts[1]
if len(p1.link_edges) != 1:
p1, p2 = p2, p1
link_edges = p2.link_edges
len_link = len(link_edges)
if len_link > 2: # complex path
list_coords.append(coords)
bpy.ops.object.mode_set(mode = 'OBJECT')
continue
elif len_link == 1:
list_coords.append([*p1.co], [*p2.co])
bpy.ops.object.mode_set(mode = 'OBJECT')
continue
if link_edges[1] == first_edge:
next_edge = link_edges[0]
else:
next_edge = link_edges[1]
coords.append([*p1.co])
coords.append([*p2.co])
# print(p1.co)
# print(p2.co)
all_edges = [e for e in edges]
all_edges.remove(first_edge)
while all_edges:
p1 = p2
first_edge = next_edge
# print(p1.co, first_edge.verts[0].co, first_edge.verts[1].co)
if p1 == first_edge.verts[0]:
p2 = first_edge.verts[1]
else:
p2 = first_edge.verts[0]
# print(p2.co)
link_edges = p2.link_edges
len_link = len(link_edges)
if len_link > 2: # complex path
coords.clear()
break
elif len_link == 1:
coords.append([*p2.co])
break
if link_edges[1] == first_edge:
next_edge = link_edges[0]
else:
next_edge = link_edges[1]
coords.append([*p2.co])
all_edges.remove(first_edge)
else:
# one vert only
verts.ensure_lookup_table()
coords.append(verts[0].co.copy())
list_coords.append(coords)
bpy.ops.object.mode_set(mode = 'OBJECT')
for obj in islands:
obj.select_set(True)
bpy.ops.object.delete(use_global=True, confirm=False)
# -- restore selected data
for obj in old_selected:
obj.select_set(True)
bpy.context.view_layer.objects.active = context_obj_old
# -- restore selected data END
print("### This is local space ###")
for coords in list_coords:
print("[")
for v in coords:
print(" ",v)
print("]")
print("")
if list_coords[0][0] == list_coords[0][-1]:
print("list in index 0 is closed path, else it has two vertices on the same position")
else:
print("list in index 0 is not closed path")
print("-- END --")
