Rendering in blender dont take rotation updates of camera and light directions

Question

I'm trying to render a cube (default blender scene) with a camera facing it. I have added a spotlight at the same location as the camera. Spotlight direction also faces towards the cube. When I render, location changes take effect for both camera and spotlight but, rotations don't. scene context update is deprecated now. I have seen other update answers, but they don't seem to help. I have done some workarounds and they seem to work, but this is not the correct way.

If I render the same set of commands twice (in a loop), I get the correct render.
If I run the script from the blender's python console (only once), I get the correct render. But If the same code is run as a script inside the blender, render is again wrong.

import pdb
import numpy as np
import bpy

def look_at(obj_camera, point):
    loc_camera = obj_camera.matrix_world.to_translation()
    direction = point - loc_camera
    rot_quat = direction.to_track_quat('-Z', 'Y')
    obj_camera.rotation_euler = rot_quat.to_euler()

data_path='some folder'
locs=np.array([ 0.00000000e+00, -1.00000000e+01,  3.00000011e-06])  #Assume, (I have big array where camera and spotlight needs to be placed, and then made to look towards cube)
obj_camera = bpy.data.objects["Camera"]
obj_other = bpy.data.objects["Cube"]
bpy.data.lights['Light'].type='SPOT'
obj_light=bpy.data.objects['Light']

loc=locs
i=0
##### if I run following lines two times, correct render is obtained.

obj_camera.location = loc
obj_light.location= obj_camera.location
look_at(obj_light, obj_other.matrix_world.to_translation())
look_at(obj_camera, obj_other.matrix_world.to_translation())
bpy.context.scene.render.filepath = data_path+'image_{}.png'.format(i)
bpy.ops.render.render(write_still = True)

funakikazuyoshi · Answer 1 · 2022-03-18T16:12:22.240

You might need to call bpy.context.view_layer.update() (bpy.context.scene.update() with older versions than blender 2.8) after changing the camera orientation by obj_camera.rotation_euler = rot_quat.to_euler() and make sure that the layers that are going to be rendered are active when calling update() (see here https://blender.stackexchange.com/questions/104958/object-locations-not-updating-before-render-python).

(A bit late ;-) but this was one of the rare questions I found for a related issue.)

Rendering in blender dont take rotation updates of camera and light directions

1 Answers1