Matte paintings are generally referred as paintings which are made in traditional manner or created digitally along with photographs which serve as background plates for keyed or rotoscoped elements in visual effects (VFX) shots.
The original mattes were nothing more than pieces of black material, cut to shape and positioned in front of a camera in order to blank out part of a frame for later enhancement. Thus the use of the term matte painting to describe the artwork created to fill in the blank. As for combining the painting with the live-action, a common solution was to double-expose the artwork into the blank space left in the original footage, while masking the already-exposed portion of the frame with a counter-matte to protect it from further exposure.
Paint has now been superseded by digital images created using photo references, 3D models, and drawing tablets. Matte painters combine their digitally matte painted textures within computer-generated 3D environments, allowing for 3D camera movement.
Throughout the 20th century, matte painting continued to thrive, enhancing the look of the films. As they developed their craft, matte painters were constantly trying out new techniques to stop their paintings looking like, well, paintings. They used layered artwork to create a greater illusion of depth. They devised cunning animated gags to simulate movement in the waves of a painted sea, or used backlighting to create convincing flares around a setting sun.
Astonishingly, despite all the changes that have swept through the effects business over the decades, matte painting is still a recognized and thriving discipline. Nowadays, of course, it’s called digital matte painting or DMP and on the face of it bears little resemblance to what was practiced by those early paintbrush-wielding pathfinders.
A modern digital matte painting is created by mapping artwork on to CG geometry. Textures for a DMP might be collages assembled from reference photography, perhaps taken on location or on the set, or artwork created from scratch. The digital matte artist refines these with retouching and hand-painting techniques, using software to create files that can subsequently be wrapped around the necessary geometry.
For the matte-painting lovers, this discipline is going to stay.