2. Motion capture.
Motion capture is the process of
recording a live motion event and
translating it into actionable data
that allows for a 3d recreation of
the performance. In other words,
transforming a live performance
into a digital performance.
In motion capture sessions, movements of
one or more actors are sampled many
times per second. Whereas early
techniques used images from multiple
cameras to calculate 3D positions, often
the purpose of motion capture is to record
only the movements of the actor, not his or
her visual appearance. This animation data
is mapped to a 3D model so that the model
performs the same actions as the actor.
3. Motion capture history… Rotoscoping.
• For either broadcast video or Internet
streaming video, rotoscoping is the rotated
projection of a sequence of usually
photographed action image frames so that
the artist can trace from the frame or create
an image to superimpose on it. It can be
thought of as "painting on movies"
efficiently. Prior to computers, an animation
stand called a Rotoscope was used to
project a sequence of action frames against
a surface so that a set of animation frames
could be traced or created. The same work
can now be done with digital images and
special computer software. Tools that
provide efficient ways to rotoscope include
Digital Magic and Elastic Reality.
Rotoscoping is frequently used as a
technique for combining (compositing)
cartoon figures with realistic settings in
television commercials and is also used for
special effects in feature-length films.
4. Motion capture pipeline.
• The motion capture pipeline consists of planning,
shooting, data processing, skeleton creation, and
mapping to characters. The most important point
about using motion capture is to avoid problems
by planning well ahead.
• After the shoot, data processing consists of
reconstructing the data from the different camera
views to produce 3D positional data and labeling
the markers. Once this has been done any noise
in the data needs to be filtered and gaps in the
data due to occlusion of markers needs to be
filled.
5. Feature Films
• Motion capture has been used extensively in feature films in
the last ten years. Some examples of its use include for digital
extras in the Titanic, digital stunts in Batman and Robin, facial
capture in the Real Adventures of Johnny Quest, lead
actor/fight scenes in The Mummy and The Mummy Returns
and finally for multiple lead characters in Final Fantasy. Large
fight scenes in LOTR as well as the Gollum character from the
Twin Towers.
6. Motion Retargeting
• An important subject in animation that has developed over
the last 10 years is that of motion retargeting
• The idea is to take an animation clip designed for one
particular character and adapt it to play on a different
character
• Characters may differ:
– Proportionally (same skeleton layout but with different
offsets)
– Topologically (different skeleton topology and different
offsets)
• This is a difficult subject because there isn’t always a
‘correct’ solution, and so heuristics must be used.
7. Sequencing & Scripting
• State machines and scripting languages are popular
methods for controlling the behaviors of characters
over longer periods of time
• Some modern state machine approaches can take a
bunch of uncorrelated motion captured clips and
automatically construct an appropriate state machine
• For example, one can motion capture a bunch of
generic moves: walk, run, turn, walk & turn, climb
steps, walk backward, hop up, hop down…
• The system then determines which moves could
connect up based on various metrics
• The actual motion can then be refined with
sophisticated warping & blending schemes
8. Artificial Intelligence
• AI is used more and more for complex
animation control
• It is often used to control large numbers of
background characters
• Obviously, there are numerous AI techniques,
and it is an entire subject itself
