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

You can:

1. Sum the vert coordinates
2. Make that the origin
3. Shift the matrix back accordingly

    import bpy
    from mathutils import Matrix, Vector
    
    scene = bpy.context.scene
    
    mesh_obs = [obj for obj in scene.objects if obj.type == 'MESH']
        
    for obj in mesh_obs:
        d = obj.data
        mw = obj.matrix_world
        origin = sum((vert.co for vert in d.vertices), Vector()) / len(d.vertices)
    
        T = Matrix.Translation(-origin)
        d.transform(T)
        mw.translation = mw @ origin

Alternatively, change your mesh creation class, such as not to use global coordinates.

Operators and Context

Operators use the context. 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 how this matters to performance.

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

...create all of the features that I want

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

Blender 3.2+

    import bpy
    
    C = bpy.context
    scene = C.scene
    
    mesh_obs = [obj for obj in scene.objects if obj.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 = [obj for obj in scene.objects if obj.type == 'MESH']

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