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I have a lot of 3D objects of various sizes, shapes in blender 2.76b and I would like to set the origin to the bottom center of the objects bounds.
I cannot select the bottom edge and snap to cursor etc as each shapes edges are in different X/Y positions.
Is there a script or tool that will allow me to set the origin to the lowest edge z position?
Move the origin to bottom of all selected mesh objects.
EDIT updated for 2.8. See prior revision for prior.
Object mode script. Moves origin to bottom of mesh, leaving object in place. Pass the matrix world to move origin to global z.
Looks at the 8 coords of objects bounding box. The bounding box is in local coordinates. To change space pass a matrix. eg the matrix world of the object will determine lowest z in global space.
o is the bounding box center. Set o.z for new origin from min z of bounding box points.
Transform all vertices by -o
Move the object back globally by o to keep the object in place.
import bpy
from mathutils import Matrix, Vector
def origin_to_bottom(ob, matrix=Matrix()):
me = ob.data
mw = ob.matrix_world
local_verts = [matrix @ Vector(v[:]) for v in ob.bound_box]
o = sum(local_verts, Vector()) / 8
o.z = min(v.z for v in local_verts)
o = matrix.inverted() @ o
me.transform(Matrix.Translation(-o))
mw.translation = mw @ o
for o in bpy.context.scene.objects:
if o.type == 'MESH':
origin_to_bottom(o)
#origin_to_bottom(o, matrix=o.matrix_world) # global
With some numpy
The global version above drops in global z direction from bbox center of geom, which can lead to an origin outside the bounding box.
Instead here is a version that finds all z minima and sets the origin to their mean
from mathutils import Matrix, Vector
import numpy as np
def origin_to_bottom(ob, matrix=Matrix(), use_verts=False):
me = ob.data
mw = ob.matrix_world
if use_verts:
data = (v.co for v in me.vertices)
else:
data = (Vector(v) for v in ob.bound_box)
coords = np.array([matrix @ v for v in data])
z = coords.T[2]
mins = np.take(coords, np.where(z == z.min())[0], axis=0)
o = Vector(np.mean(mins, axis=0))
o = matrix.inverted() @ o
me.transform(Matrix.Translation(-o))
mw.translation = mw @ o
This could be further enhanced by using methods outlined in this excellent Q / A
Replace matrix @ vector list comprehensions with something more efficient
Note: Remember objects can share a mesh. The test code above runs over all mesh objects in the scene without checking for this.
Just wanted to add this here:
bl_info = {
"name": "Origin to...",
"author": "Martynas Žiemys",
"version": (1, 0),
"blender": (3, 4, 1),
"location": "3D Viewport, Alt+Shift+Ctrl+D",
"description": "Moves the origin point to top, botom and sides of objects' bounding boxes in global space.",
"category": "Pie Menus",
}
import bpy
from mathutils import Vector
from bpy.props import (
BoolProperty,
EnumProperty,
)
class OBJECT_OT_origin_to(bpy.types.Operator):
"""Move the origin to top, botom or sides(global space)"""
bl_idname = "object.origin_to"
bl_label = "Origin to..."
bl_options = {'REGISTER', 'UNDO'}
center: BoolProperty(
name="Center in other axis",
description="Center in other axis",
default=True,
)
move: BoolProperty(
name="Move to 3D Cursor",
description="Move to 3D Cursor",
default=False,
)
sides = (
('X', "X", "X"),
('-X', "-X", "-X"),
('Y', "Y", "Y"),
('-Y', "-Y", "-Y"),
('Z', "Z", "Z"),
('-Z', "-Z", "-Z"),
)
side: EnumProperty(
name="Side",
items=sides,
default='-Z',
)
@classmethod
def poll(cls, context):
return context.object is not None
def execute(self, context):
switch_mode = False
if context.mode != 'OBJECT':
switch_mode = True
bpy.ops.object.mode_set(mode='OBJECT', toggle=True)
for o in context.selected_objects:
if o.type == "MESH":
override = bpy.context.copy()
override["object"] = o
with bpy.context.temp_override(**override):
bpy.ops.object.transform_apply(
location=False,
rotation=False,
scale=True,
properties=False
)
d = o.data
m = o.matrix_world
if self.center:
bounds_center = (sum((m @ Vector(b) for b in o.bound_box), Vector()))/8
difference = m.translation - bounds_center
local_difference = difference @ m
for v in d.vertices:
v.co += local_difference
m.translation -= difference
difference = Vector((0,0,0))
if self.side == 'X':
bound = max((m @ v.co).x for v in d.vertices)
difference.x = m.translation.x - bound
elif self.side == '-X':
bound = min((m @ v.co).x for v in d.vertices)
difference.x = m.translation.x - bound
elif self.side == 'Y':
bound = max((m @ v.co).y for v in d.vertices)
difference.y = m.translation.y - bound
elif self.side == '-Y':
bound = min((m @ v.co).y for v in d.vertices)
difference.y = m.translation.y - bound
elif self.side == 'Z':
bound = max((m @ v.co).z for v in d.vertices)
difference.z = m.translation.z - bound
elif self.side == '-Z':
bound = min((m @ v.co).z for v in d.vertices)
difference.z = m.translation.z - bound
local_difference = difference @ m
for v in d.vertices:
v.co += local_difference
m.translation -= difference
if self.move:
o.location = context.scene.cursor.location
if switch_mode:
bpy.ops.object.mode_set(mode='OBJECT', toggle=True)
return {'FINISHED'}
class VIEW3D_MT_PIE_origin_to_pie(bpy.types.Menu):
bl_idname = "VIEW3D_MT_origin_to_pie"
bl_label = "Origin to..."
def draw(self, context):
layout = self.layout
pie = layout.menu_pie()
op = pie.operator("object.origin_to", text = "Origin to Left(-X)")
op.side = '-X'
op.move = False
op = pie.operator("object.origin_to", text = "Origin to Right(X)")
op.side = 'X'
op.move = False
op = pie.operator("object.origin_to", text = "Origin to Bottom(-Z)")
op.side = '-Z'
op.move = False
op = pie.operator("object.origin_to", text = "Origin to Top(Z)")
op.side = 'Z'
op.move = False
op = pie.operator("object.origin_to", text = "Origin to Back(Y)")
op.side = 'Y'
op.move = False
op = pie.operator("object.origin_to", text = "Origin to Top and cursor")
op.side = 'Z'
op.move = True
op = pie.operator("object.origin_to", text = "Origin to Front(-Y)")
op.side = '-Y'
op.move = False
op = pie.operator("object.origin_to", text = "Origin to Bottom and cursor")
op.side = '-Z'
op.move = True
addon_keymaps = []
def register():
bpy.utils.register_class(OBJECT_OT_origin_to)
bpy.utils.register_class(VIEW3D_MT_PIE_origin_to_pie)
kcfg = bpy.context.window_manager.keyconfigs.addon
if kcfg:
km = kcfg.keymaps.new(name='3D View Generic', space_type='VIEW_3D')
kmi = km.keymap_items.new("wm.call_menu_pie", 'D', 'PRESS', any=False, alt=True, ctrl=True,shift=True)
kmi.properties.name = "VIEW3D_MT_origin_to_pie"
addon_keymaps.append((km, kmi.idname))
def unregister():
for km, kmi_idname in addon_keymaps:
for kmi in km.keymap_items:
if kmi.idname == kmi_idname:
km.keymap_items.remove(kmi)
addon_keymaps.clear()
bpy.utils.unregister_class(VIEW3D_MT_PIE_origin_to_pie)
bpy.utils.unregister_class(OBJECT_OT_origin_to)
if __name__ == "__main__":
register()
# test calls
#bpy.ops.object.origin_to()
#bpy.ops.wm.call_menu_pie(name="VIEW3D_MT_PIE_origin_to")
That's made into a little add-on, that if saved to a file with .py extension from Blender's text editor(utf-8 encoding) can be installed as any add-on and creates a pie menu called with Alt+Ctrl+Shift+D:
I wanted to make it for myself for quite some time to help me with placing objects in my scene like ceiling lights, chairs, books or accessories on shelves and so on. I suppose you do not need to manipulate the origin for that, but I find it convenient so since I wrote it now and it's quite related to the question, I can share it here. It works on all selected objects and if you happen to be in edit mode, it switches back and forth as well.
here is a script working in object mode or in edit mode but notice if there are some shape keys, we have to go in edit mode
import bpy, bmesh
from bpy import context
from mathutils import Matrix, Vector
cao=bpy.context.active_object
me = cao.data
mw = cao.matrix_world
difference = Vector((0,0,0))
local_verts = [mw @ Vector(v) for v in cao.bound_box]
o = sum(local_verts, Vector()) / 8
o.z = min(v.z for v in local_verts)
difference = mw.translation - o
#difference.z = mw.translation.z - o.z #only z
local_difference = difference @ mw
if context.object.mode == 'OBJECT':
if me.shape_keys:
# select basis
cao.active_shape_key_index = 0
bpy.ops.object.editmode_toggle()
bm = bmesh.from_edit_mesh(me)
for v in bm.verts:
v.co += local_difference
bpy.ops.object.editmode_toggle()
else:
for v in me.vertices:
v.co += local_difference
else:
bm = bmesh.from_edit_mesh(me)
for v in bm.verts:
v.co += local_difference
bmesh.update_edit_mesh(me)
mw.translation -= difference
```
This script will move the origin to the median point of the vertex/vertices with the lowest Z value (not necessarily the bottom center of the object).
Copy this script to Text window and Run Script, this will work in Edit mode and object mode, results:
1- Object mode is activated in the end result.
2- Origin set to the median point of the vertex/vertices with the lowest Z value.
4- 3D cursor is set at the new origin.
import bpy
def select_lower_Z():
o = bpy.context.object # active object
mw = o.matrix_world # Active object's world matrix
glob_vertex_coordinates = [ mw * v.co for v in o.data.vertices ] # Global coordinates of vertices
bpy.ops.object.mode_set(mode = 'EDIT') #Change mode of selected object to Edit mode
bpy.ops.mesh.select_mode(use_extend=False, use_expand=False, type='VERT') #Set the type in Edit mode to Vertices
bpy.ops.mesh.select_all(action = 'DESELECT') #Deselect all
bpy.ops.object.mode_set(mode = 'OBJECT') #Change mode of selected object to Object mode
# Find the lowest Z value amongst the object's verts
minZ = min( [ co.z for co in glob_vertex_coordinates ] )
# Select all the vertices that are on the lowest Z
for v in o.data.vertices:
if (mw * v.co).z == minZ:
v.select = True
bpy.ops.object.mode_set(mode = 'EDIT') #Change mode of selected object to Edit mode
current_area_type = bpy.context.area.type#Save the current area type to a variable
area = bpy.context.area #Change the area to 3D view in order to get rid of wrong context error
old_type = area.type #Change the area to 3D view in order to get rid of wrong context error
area.type = 'VIEW_3D' #Change the area to 3D view in order to get rid of wrong context error
bpy.ops.view3d.snap_cursor_to_selected() #Move the cursor to selected
bpy.ops.object.mode_set(mode= 'OBJECT') #Set the mode back to Object mode
bpy.ops.object.origin_set(type='ORIGIN_CURSOR') #Move the selected object origing's to the 3D cursor's location
bpy.context.area.type = current_area_type #Set the area type back to what it was before changing it to 3D view
select_lower_Z()
