Setting the origin for each object to geometry

Question

Blender 2.83

In python I can create all of the features that I want in my world, but when I go to the world, each thing has the same location data. I can click on each and click set origin to geometry, and that fixes it. The info pane says:

bpy.ops.object.origin_set(
    type='ORIGIN_GEOMETRY',
    center='MEDIAN'
)

So I would think I can run, at the end of my script, something like:

for object in bpy.context.scene.objects:
    bpy.ops.object.origin_set(
        type='ORIGIN_GEOMETRY', 
        center='MEDIAN'
    )

but this doesn't seem to do anything. How do I set everything to have origin_geometry, so that they have reasonable position data?

Answer 1

Low level Origin to geometry

Will have to investigate the difference between calling the set origin operator via code and via the UI

Instead can sum the vert coordinates make that the origin, and shift the matrix back accordingly

import bpy
from mathutils import Matrix, Vector

scene = bpy.context.scene

mesh_obs = [o for o in scene.objects if o.type == 'MESH']


for o in mesh_obs:
    me = o.data
    mw = o.matrix_world
    origin = sum((v.co for v in me.vertices), Vector()) / len(me.vertices)

    T = Matrix.Translation(-origin)
    me.transform(T)
    mw.translation = mw @ origin

Alternatively could change your mesh creation class to not use global coordinates.

Operators run on context

Operators use the context. The origin set will set the origin of all selected mesh objects and can be run once on the selection rather than per object. See Python performance with Blender operators as to why this matters.

Another part of context is the code in question? It is quite possible that changing the origin could be dealt with somewhere else if you are to quote:

In python I can create all of the features that I want

However without any idea of what prior code is, here is a Test script, set origin of all mesh objects in the scene by passing them as overridden context to the operator.

Blender 3.2+

import bpy

C = bpy.context
scene = C.scene

mesh_obs = [o for o in scene.objects if o.type == 'MESH']
c = {"object" : mesh_obs[0],
    "selected_objects" : mesh_obs,
    "selected_editable_objects" : mesh_obs}
    
if mesh_obs:
    with C.temp_override(**c):
        bpy.ops.object.origin_set()

Blender 2.8+

import bpy

scene = bpy.context.scene

mesh_obs = [o for o in scene.objects if o.type == 'MESH']

if mesh_obs:
    bpy.ops.object.origin_set(
            {"object" : mesh_obs[0],
            "selected_objects" : mesh_obs,
            "selected_editable_objects" : mesh_obs,
            }
        )