by GrahamKennedy » Mon Sep 06, 2010 11:11 pm
Having seen a lot of the extras on TNG DVDs....
Take a flyby by the Ent-D compared to the Ent-nil.
For the E nil, a guy pushes the camera past the model and films it. Then they replace the blue background with a shot of space using colour substitution.
In the Ent D, they might have the ship making a nice lovely curve through space as it orbits some planet or whatever. To do that, they keep the model still and pan the camera past on rails.
But that's only part of it. You do that for the model. But now you need all those little window lights. You black out the scene and do the same pan past, this time with the model's inside lit up so the window lights show up.
Now you do it again, with nothing but the nacelles lit up.
Now you do it again, with nothing but the deflector dish lit up.
Now you composit all those images on top of one another, and put it on top of a background image, and that's how you get what you see on screen.
And to do this, the camera has to move and pan past the model in EXACTLY the same way every time. That means that rather than have some guy simply shove it past, you have to have a computer attached to the motors on the rail and on the tilt and pan of the camera, so that it can run that camera down those rails tilting and panning it precisely the same, every time.
If there's another ship in this image and it's moving independently of the E-D - a shuttle, say - then you have to repeat the entire process all over again for that ship. And indeed for every and any moving object in the image. In fact it was only with the invention of computer controled movement that it became possible to have things like spaceships moving independently of one another in FX shots. 2001 is a truly beautiful rendition of Things In Space but not once do you see any two ships move relative to one another, because it wasn't until a couple of years later that Lucas invented the technique so he could have space dogfighting in Star Wars.
As you can imagine, this is an insanely time consuming and expensive effort. One single 10 second shot of the E-D flying past probably takes a whole crew several days and tens of thousands of dollars to film.
Of course, nowdays you do it all in a computer and the expense is in hiring many animators and buying computer rendering time or machines. But that has it's own costs. I remember an episode of Stargate where O'Neill walked through the gate. On a whim, the actor turned and tapped the event horizon with his finger before walking on and doing the rest of the scene. The following week he got an irate call from the FX department; "We had to re-render the iris footage to add ripples around your finger. It took two days and fifteen thousand dollars of rendering time! Please don't ever do that again!"
Give a man a fire, and you keep him warm for a day. SET a man on fire, and you will keep him warm for the rest of his life...