thanks Ferdinand this cleared things up for me

hi there,
I managed to get a script working that can select and hide polygons that are outside of the camera frustrum as well as polygons that are behind other polys along a camera path. I’m using the ray collider to detect what poly face has been hit from the camera's position and then selecting this with the polygon selection tag.
I am now trying to use threading in python to split the ray hits calculations between my computer’s threads so that I can speed up the script’s running time. Having some issues at the moment with getting the script to show the selected polys. It works when threading is False, but not sure what I am doing wrong in my setup for when threading is true, any help would be much appreciated

attached is a test file and the python script which runs in the script manager220608_occlusion_frustrum_threaded02.py
A220608_model with path 2.c4d