The
process of 'visual effects' is through use motion-tracking software
to apply points to a piece of video footage that track the movement
of the objects in the video and attempts to guess the movement of the
camera in a 3D environment. This creates a theoretical path for the
camera and this path can be applied to a camera in a 3D animation
program. This is used when a company wishes to create CG characters
and put them into a live-action scene that has a moving camera,
because the movement of the live-action camera and the 3D camera are
the same the CG character or object will be filmed in exactly the
same way the live-action scene was and so will appear as though it is
a part of the scene instead of a 3D object with a live-action video
as a background.
There
are various programs with which this can be accomplished such as:
Blender, Voodoo, Icarus, Autodesk Matchmover, REAL VIZ Matchmover and
many others. One of the programs most used in industry I assume would
be Autodesk Matchmover as it comes as part of the Autodesk suite
which includes Autodesk Maya, a 3D modeling and animating software.
After
the footage and animation have been combined inside the chosen 3D
animation software it is very helpful to be moved into a compositing
program such as Autodesk Composite, which is also available as part
of the Autodesk suite, in these programs the user can alter the
elements of the 3D animation such as the strength of the lighting,
strength of colours, size and strength of shadows, even the
transparency of the 3D characters and objects. This is useful as
these elements can be altered and previewed in this program instead
of rendering out the animation multiple times to see how it looks if
the elements are altered and makes creating the final output a lot
less time consuming and a little easier.
When
filming for a movie that requires CG objects or characters added a
lot of things need to be concidered. The main two that come to mind
are the types of shots intended to be filmed with the camera, and the
lighting of the scene. These are possibly the most crucial as the
camera movement and lighting need to be re-created in the 3D
animation later. The lighting is not as much of a worry as long as it
is re-creatable as it can be mimicked in the 3D modelling/animation
software, but the camera movement could cause large problems for the
motion tracking software if the camera moves to quickly or have
unusual movements or angles, if the camera shot is to fast and the
motion tracking software does not correctly calculate the cameras
movement or position then the motion path will be wrong and the 3D
animated character or object will not fit into the scene.
Still/static shots are not an issue because if the camera does not
move in the scene then the 3D camera does not need to move, however
if the camera shot is an over-head angle looking down and moves to a
low angle shot looking at the same scene but from the side, that
could confuse the motion tracking software especially if the footage
from the camera movement has too much blur in it.
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