Matchmoving

Anytime a computer-generated (CG) element needs to be placed into a live-action sequence vice versa, a matchmove is required. But what exactly is matchmoving?Matchmoving is the process of matching CG elements into live-action footage. As a result,crucial part of many visual effects shots.Despite its importance, it is completely invisible in final shot—that is, if it’s done right.

In cinematography, match moving is a special effects technology to allow the insertion of virtual objects into real footage with the correct position, scale, orientation and motion in relation to the photographed objects in the scene. The term is used loosely to refer to several different ways of extracting motion information from a motion picture, particularly camera movement. Match moving is related to rotoscoping and photogrammetry. It is sometimes referred to as motion tracking.

Match moving has two forms.
Compositing programs, such as Shake, Adobe After Effects and Discreet Combustion, have two dimensional motion tracking capabilities. This feature translates images in two-dimensional space and can add effects such as motion blur in an attempt to eliminate relative motion between two features of two moving images. This technique is sufficient to create verisimilitude when the two images do not include major changes in camera perspective. For example a billboard deep in the background of a shot can often be replaced using two-dimensional tracking.
-Voodoo (freeware)
-Icarus (University of Manchester research project, now discontinued but still popular)
-3DS max
-Maya Live (Module of Maya Unlimited)
-The Pixel Farm PFTrack
-PFHoe (Cost effective matchmover based on PFTrack algorithms)
-RealViz MatchMover
-Science.D.Visions 3DEqualizer (which won an academy award for technical achievement)
-Andersson Technologies SynthEyes
-2d3 Boujou

Three dimensional match moving tools make it possible to extrapolate three-dimensional information from two-dimensional photography. Programs capable of 3D match moving include:
These programs allow users to derive camera movement and other relative motion from arbitrary footage. The tracking information can be transferred to computer graphics software such as Blender, Maya or Lightwave and used to animate virtual cameras and CGI objects.

The first, and still some of the best, examples of match moving were used in the film Jurassic Park. The filmmakers placed colored tennis balls in the scene as reference marks. They then used these marks to track the motion of the camera through the scene. This allowed virtual objects, such as CGI dinosaurs, to be added to complicated camera movements and even handheld shots. The tennis balls were later digitally painted out of the final shot.