Re: Holodeck
> They actually shoot the actors on green screen and use a computer to replace the green (color humans don't have) with whatever CG decor they want.
Not anymore, at least in TV. Green screen takes a lot more acting skill and rehearsal time. If you have to look at the dinosaur in the background you either have to have a man with a tennis ball on a fishing rod and you have to do 30 takes so your eyes track the right position - or you have a dinosaur on the background.
It's also a lot quicker and cheaper in post - matting in background is 95% automated but the last hand tweaks when you have close-ups of hair or you need to do color tweaks is time consuming if you are doing a weekly show.
And the lighting is easier, if there is a light in the scene and it's on a high brightness background screen the real light of the right color falls on the actors face in the right way - you don't need to fix it in post.
The really cool bit is that the backgrounds are generated in a games engine and tied to the camera track, so when the camera moves the perspective view of the background moves with it.