Python: Low level apply rotation to an object

Question

How to apply rotation directly to an object in Python (not BGE, not bpy.ops...)?

import bpy
import mathutils
from mathutils import*

obj = bpy.context.active_object
obj.rotation_euler = Vector([0, 0, 45])

#obj.apply_rotation
#Apply rotation like CTRL+A -> Rotation

Thanks!

I need a method for an object that's been already rotated like in my example code.

Answer 1

To apply transformation really low-level, you should probably set the object's matrix directly and avoid bpy.ops.object.transform_apply() entirely:

import bpy
from math import radians
from mathutils import Euler, Matrix

euler = Euler(map(radians, (0, 0, 45)), 'XYZ')

ob = bpy.context.object

loc, rot, scale = ob.matrix_world.decompose()

smat = Matrix()
for i in range(3):
    smat[i][i] = scale[i]

mat = Matrix.Translation(loc) * euler.to_matrix().to_4x4() * smat

ob.matrix_world = mat

Change the last line to ob.matrix_local = ob.matrix_parent_inverse * mat if you want to set a rotation of 0°, 0°, 45° (as seen in Object tab) even if the object is parented.

The code might need further adjustments if drivers or modifiers are involved, non-uniform scaling in combination with parenting does not seems to work fine however.

Answer 2

Ctrl+A executes this operator:

bpy.ops.object.transform_apply( rotation = True )

Answer 3

I would do this in bmesh with each vertex and then reset the object transformation:

rObj = bpy.context.object
vScale = mathutils.Vector(rObj.scale)
vLocation = mathutils.Vector(rObj.location)
rObj.scale = (1.0,1.0,1.0)
rObj.location = (0,0,0)
bm = bmesh.new()
bm.from_mesh(rObj.data)
for v in bm.verts:
  v.co = rObj.matrix_world * v.co
bm.to_mesh(rObj.data)
bm.free()
rObj.rotation_euler = (0,0,0)
rObj.scale = vScale
rObj.location = vLocation