Elements moving in mattepaintings for films

[cserbuj]

Hi everyone!

I often see mattepaintings, with elements that are moving, they have action on it. By example, waterfalls. When i see them in films, the waterfall is moving...but when i see the matte in many forums, they include a waterfall, but is an static image.
My question is: the waterfall in the painting really is not used in film? it combines a real waterfall filmed, using masks?

I would like to know how is the process most of times. Sometimes, theese elements are very integrated in the matte, and maybe it is very difficult to separate with masks.
Thanks in advance.

[Eisner]

This is mainly achieved in 3d as particles. A camera move and the projection geometry will be used as a reference, then the particles are added in the composite stage.

[Da_Elf]

strange. thats almost the exact same thing i was asking two posts down

[Dream Artisan]

And not infrequently, these elements (like explosions) are also made by shooting them live on a soundstage against a black background. If you paint these moving elements into your "matte", it ceases to be a true matte painting and becomes more of an illustration.

[cserbuj]

I see....thanks for your replies.

[dstipes]

When appropriate, I still like to encourage the use of live action elements. For example shooting salt or sugar pouring over black to burn into the painting to simulate the water fall.

The organic randomness of "real world" elements can sometimes be better than CGI particle animation.

(If not better, then still fun to shoot.) :wink:

David

[rrische]

I agree totally with David. We both come from the days
of traditional effects, and as much as CG can be exciting,
when I'm working on a shot I always look to using real
things first. Why? They're REAL. Having a library of real
motion elements is a very good thing.
But just using real elements won't guarantee a good result.
They have to be composited well also.

[cserbuj]

OK, thanks Rick and David.
Really, there are many solutions, i know. I suppose that is like the process of mixing layers in photoshop, creating masks. But with live shooting. Put that part of that filmed action here, and this one here, with good composition.
But when camera is moving,....i imagine that you need to use rotoscopy. frame to frame? or is there a way to "mask" a moving part of a film without doing it frame to frame?

[rrische]

Just as Photoshop has automated masking tools (magic wand,
color range selection tool et. al.), compositing programs like
After Effects also have automated ways of isolating elements
in running footage. Shooting your elements against blue/ green
screen will enable you to pull a matte fairly easily, also.
Rotoscoping is probably the last choice as it's the most labor-
intensive. But it allows the most precise control and let's you
create a matte you couldn't get any other way (like pulling
one person out of a crowded street scene, say).

For some shots in "The Mummy Returns", I went out with a
standard def digital video camera and shot some full frame
blowing tree elements. It was overcast that day, and it wasn't
particuliarly hard to pull mattes off them in After Effects just
using standard keying tools. Once I had the trees extracted,
I could place them anywhere I wanted in the paintings.

[cserbuj]

Great, Rick, your explanations very clear, as always.
I see, there are ways to isolate in running footage. But, rotoscopy always is frame to frame? Is to do masks manually, frame to frame, guiding the element i want to isolate?

[rrische]

Correct. Rotoscoping = tracing something by hand, frame by frame.

[Da_Elf]

been there done that hated it hehee. next time we needed to do it i hired two lackeys to do all the work

[rrische]

been there done that hated it hehee. next time we needed to do it i hired two lackeys to do all the work

Lackeys= :(
Always respect your help :D

[Da_Elf]

oh naturally i respected them. they hated every minute of the work. but i did take them out for a nice dinner and drinks when it was all done. plus they were paid nicely