Whenever I meet someone new I tend to shy away from the subject of occupation. Not because I am not interested in what the person does. Often what a person does can tell a lot about them. I am trying to avoid explaining what I do. But because of our societal social norm, eventually the question is asked. "So, what do you do?"
Depending on the situation or my mood, I then decide on how I am going to proceed. Sometimes its very general. "I'm an artist" But this is almost like saying "i'm an athlete" it really does not tell them what I do. I also may say something like "I work in animation" But again, this too is very general and most people do not know what that entails. We are used to an answer we can understand like "plumber" or "doctor" or even "super secret spy" we have an idea of what those people do.
When I am feeling up for the challenge, I say "I am a Matte Painter" . The typical response is "MAP painter"? and although I have painted a map before, I say "no, MATTE painter". Then begins trying to explain what it is.
This is the Wikipedia definition of matte painting:
A matte painting is a painted representation of a landscape, set, or distant location that allows filmmakers to create the illusion of an environment that is not present at the filming location. Historically, matte painters and film technicians have used various techniques to combine a matte-painted image with live-action footage. At its best, depending on the skill levels of the artists and technicians, the effect is "seamless" and creates environments that would otherwise be impossible or expensive to film. In the scenes the painting part is static and movements are integrated on it.
I would also add to this that it is not limited to a distant location and I have done many paintings as close to the camera as painting directly on a the actor's face. And also, it is not always static or stationary.
This Wikipedia definition also does not cover animated films. It works very much the same as in live action films. A matte painting can greatly expand the wolrd of an animated film. In many cases it would be thought too expensive to build a set that extends far into the distance in the same manner it is built for the close up shots. A matte painting can provide the needed vista.
This is possible because of the matte painting process. Back in the day (Raiders of the lost ark and Star Wars a New Hope comes to mind) these paintings were done on glass and masson board and shot with miniatures. Today we have advanced to digital painting techniques and integration methods. Since it is a "painting" and not actual geometry it takes little time for the render computers to render the painting portion on the frame, therefore making it significantly cheaper to create. And it usually takes less time to create because it is done by only one artist. If done by the traditional production pipeline, it needs to go through several departments and people before it is ready to render, saving even more cost.
There is no set method to a matte painters madness. Anything goes. It can be as simple as a 2d photoshop painting to a full 3d modeled environment. If you have ever seen the "making of" on the extra segments on a DVD you have probably seen a matte painting in action. You see the actors or set with a green screen behind them and then the environment that replaces the green is revealed. That is a usually a matte painting.
This example is from the movie RIPD
The background buildings and were done in photoshop. Then placed on 3d geometric boxes to give it dimensionality.