Special and Visual Effects : Rendering in reverse

Rendering in reverse

To make a CGI character or object, you need to first create the design, the shape and form, how it's gonna look. Then you add texture, colors, light and shadow and so on.

Is it possible to do it the other way around, using real life actors? Take away all of it, so that only their shape and form remains? The reason why I'm asking is because when filming a scene taking place in a non-existant place, they actors are usually standing in front of a green screen or something. Then the backgrounds are added later.

But the characters are more or less the same. If they are supposed to be standing somewhere in sharp sunlight, you can't film them in front of a green screen in dim light. Or film them in sharp light if they are inside a dark building. Or film them with the light coming from left, when the sun in the background is supposed to be right over their heads. Or if they are walking under a blue sky, the light can't have the same colors as if they were walking under a green spotlight.
The light on stage need to spread in the same way as the light in the background, have the same colors and intensity, and come from the same directions. That's a lot of work to make it all fit together.

So what if you have live action characters and objects in from of the screen that have been "re-rendered", for the lack of a better word, and then rendered together with the backgrounds? Wouldn't that both save some time and money, and make the finished product look even more convincing?

Re: Rendering in reverse

You would need a program that could consistently and effectively make distinctions between objects at the capacity or higher than that of a human. Not to mention that "re-rendering" would result in a cgi looking character with an unnatural look. Current methods are far superior due to the simple fact that post production can be used to alter lighting and environments.

Re: Rendering in reverse

I'm not sure if you understood.

Step 1:

A process similar to that of cel shading, only more advanced. Colors and such are removed.

Step 2:

Everything is rendered again as photorealistic as possible.

They use actors who are dressed much like they to in performance capture, so that clothes and hair can be added later, to make sure the hair and clothes are moving in the virtual wind in the same way as the digital trees in the background.

We could use this if making a science fiction movie taking place somewhere with lower gravity, like Drew Goddard's The Martian, but also in general filmmaking just for the sake of the aesthetics. As we saw in the Tintin movie, they have come a long way these days.