Matakuliah
Tahun
: UO666 / DKV Visual FX
: 2009
VFX Production
Pertemuan 05
The Art Of Tracking
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Bina Nusantara
Tracking is the process of automatically locating a point or
series of points from frame to frame in a sequence, allowing the
user to stablise, track to or solve object or camera movement in the
shot. The process started as one point tracking which could stablise a
shot or add matching motion to a composite. Today it involves
complex 3D camera solutions and extends to optical flow - the
technology of tracking every pixel in a shot.
The Art Of Tracking
Bina Nusantara
The Art Of Tracking
Bina Nusantara
The Art Of Tracking
2D Tracking
In looking at what tracks and how it is important
to understand one key point, most modern
trackers with the exception of Digital Fusion (and
to a lesser degree Shake and AE) have all
moved away from colour processing
approaches. Almost all trackers are now biased
to a luminance of black and white version of the
track box. Digital Fusion alone amongst the
leading packages uses colour information
automatically. When a track is performed in
Digital Fusion, the user interface shows the
stength of each of the three colour channels and
then which it has decided to use.
Bina Nusantara
The Art Of Tracking
3D Tracking
The goal of a 3D tracking program is to solve the
camera position by using two camera views. "Think
triangulation," writes Katz. Epipolar geometry is a type
of triangulation. When using photographs to determine
the position of a point on an object using triangulation,
it's necessary to match the image location point in one
image to the image location point in a second image.
Matching these pair of points in two images is called
correspondence. Finding these matches would appear
to require searching the entire image. Epipolar
geometry proposes that the point we are interested is
actually constrained to a single line. This greatly limits
the search for that point." By using the path of the point
to define a line, one can predict where a point is going
and greatly reduce the amount of computation and
hence speed up the tracking process.
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The Art Of Tracking
The issue of which tracker is best is
also effected by what the camera is
doing - large dots zooming away to
small pin points can be a problem,
camera rotation, motion blur and
depth of field can also be big factors
What is the ideal tracking marker to use on set?
Bina Nusantara