Catmull Rom Won't Display Post-Processing

I have a Catmull Rom addon for GMOD and I love it.
The coding is beautiful and I use it allot.
Yesterday, however, I fooled around with the Post Processing (In the gmod menu (Q) their is a post processing tab on the right side… yeah that one) on dm_overwatch and made sun beams, it was darker and their were fewer colors.
It looked legit, and I wanted to make a short film with it.
I make a catmull rom camera track and when I click the keypad button to view it,
the post processing is gone and everything was back to the way it was before.

Can this somehow be changed?
Or is this just how it works.
If it works like that, I’d want to see a Catmull Rom camera addon that supports Post Processing (if possible)

It can’t display post-processing and i don’t know how to make it support it. You could use some video-editing program to make post-processing effects, in-game PP lags the game anyways.

Don’t use the in-game PP, edit it later. That way it will keep its FPS, and still look good without lag.

thanks guys.