What is the Visual Effects Technique?

Green Screen: Green screening is a technique for compositing (layering) two images together. A color range in the top layer is made transparent, revealing another image behind. Also known as the chroma keying technique, it is commonly used in video production and post-production. 

Motion Tracking: Motion Tracking allows the insertion of computer graphics into live-action footage with correct position, scale, orientation, and motion relative to the photographed objects in the shot. The term is used loosely to refer to several different ways of extracting motion information from a motion picture, particularly camera movement. Motion tracking is related to rotoscoping and photogrammetry. It is sometimes referred to as match moving.  

3d Modeling: A 3d model is a representation of any three-dimensional surface of object (either inanimate or living) via a 3d modeling software such as Maya, Cinema 4d or 3Ds Max. The product is called a 3D model. It can be displayed as a two-dimensional image through a process called 3D rendering or used in a computer simulation of physical phenomena.

Matte Painting: A Matte Painting is made when we combine two or more image elements into a single, final image. Usually, mattes are used to combine a foreground image (such as actors on a set, or a spaceship) with a background image (a scenic vista, a field of stars and planets). In this case, the matte is the background painting. In film and stage, mattes can be physically huge sections of painted canvas, portraying large scenic expanses of landscapes. 

Physical Simulators: Physical simulator software allows simulation of the way bodies of many types are affected by a variety of physical stimuli. They are also used to create Dynamical simulations without having to know anything about physics. Physics engines are used throughout the video game and movie industry. They are often used for high budget films involving natural disasters such as 2012. physical simulator realflow vfx visual effects             

Rotoscoping: Rotoscoping is the process of manually altering film or video footage one frame at a time. The frames can be painted on arbitrarily to create custom animated effects like lightning or lightsabres, or traced to create realistic traditional style animation or to produce hold-out mattes for compositing elements in a scene and, more recently, to produce depth maps for stereo conversion.