#### Resources

## Motion Synthesis and Motion Library

##### Papers

Motion Synthesis By Example.
Computer Animation and Simulation.
1996.

The paper (first?) introduces an idea of motion synthesis by example,
i.e. producing a specified motion by combining a set of adjusted sample
motions stored in a database. Very inspiring ideas and questions are
discussed concerning motion database creation and usage. The approach
is illustrated on a very simple model of "Luxo", hopping across a
variable terrain.

Interpolation and extrapolation of motion capture data.
Proceedings of PRICAI.
2002.

BibTeX entry

The same dance motions captured with different styles (e.g. bright,
gloomy) are interpolated or extrapolated to achieve style exaggeration.
The joint angles are transformed by Fourier transform and interpolation
(extrapolation) is performed in Fourier spectrum. The final motion is
then produced by inverse FT on interpolated signal.

Interactive motion generation from examples.
Computer Graphics (SIGGRAPH).
2002.

Synthesis of a free human motion from a database of various motion
clips. The motion specified by constraints to satisfy is generated by
cutting and pasting portions of the clips from the database. The
portions are selected to have very similar last and first frame and the
small discontinuities around the joint are smoothed. To find appropriate
portions of the clips is a graph search problem. A pyramidal hierarchy
of simplified graphs and successive mutations of searched path are used
to speed up the search to interactive rates.

Only the motions available in the original dataset are possible to synthesize. However, also a similar motions synthesis would be very useful. Anyway, the key issue is the database choice, to be compact and allow the widest range of human motion.

Only the motions available in the original dataset are possible to synthesize. However, also a similar motions synthesis would be very useful. Anyway, the key issue is the database choice, to be compact and allow the widest range of human motion.

Motion Synthesis from Annotations.
Computer Graphics (SIGGRAPH).
2003.

BibTeX entry

Fourier Principles for Emotion-based Human
Figure Animation.
Computer Graphics (SIGGRAPH).
1995.

The Fourier image is used to represent a periodic motion and to
generate its variations. Motion transitions and exaggeration are
obtained by interpolation and extrapolation; kinematic
characteristics (e.g. speed, step length) are altered by
adjustment of Fourier coefficients and the most interesting
– difference of (Fourier images of) a "normal" motion and
the same kind of motion with a mood gives the mood characteristics
itself. Adding this mood characteristics to a different kind of
motion the mood is transfered to a new motion.

Interpolation Synthesis of Articulated Figure
Motion.
IEEE Computer Graphics and Applications.
1996.

The method is a more realistic substitution of inverse kinematics
based on interpolation of several stored poses surrounding a goal
pose. The stored poses are recorded by MC and regularly resampled.
One of the earliest works about motion synthesis from examples.

Spacetime Constraints.
Computer Graphics (SIGGRAPH).
1988.

Motion control by specifying constraints and a goal function
followed by solving a big optimization problem over the whole
time interval of the motion. Initial, final and "style"
constraints as well as the goal function to be minimized (e.g.
muscle energy) are specified by an animator, further constraints
follow from physical laws of mechanics. The optimization is solved
numerically. Example of jumping Luxo is presented.

Spacetime Constraints Revisited.
Computer Graphics (SIGGRAPH).
1993.

Producing of motion by genetic algorithms. The most successful
behaviours are selected from populations simulated in physical
environment.

Animating Human Athletics.
Computer Graphics (SIGGRAPH).
1995.

Simulation of 3 particular human motions (running, bicycling and
vaulting) by dynamics. Any new motions would require specific
analysis and respective equations formulation.

Real time responsive animation with
personality.
IEEE Transactions on Visualization and Computer
Graphics.
1995.

Human motion is produced by applying sine-wave signals to joint
angles. Moreover a noise signal is added to avoid absolutely
repetitious motion. Motion transitions are performed by interpolation
with variable S-shaped weights.

Efficient Generation of Motion Transitions using
Spacetime Constraints.
Computer Graphics (SIGGRAPH).
1996.

Creation of transitions between last frame of a motion clip and
a different first frame of a successive clip. The transition is
made by spacetime optimization over the entire time interval of
the transition. A term for inverse kinematics constraints (avoids
e.g. support foot sliding during transition) and a term for
metabolic energy (causes the motion to look natural) are both
minimized. That presents an inverse dynamics problem, not very
clear to me. Also transitions with motions defined only on a part
of body are possible.

Verbs and Adverbs: Multidimensional Motion
Interpolation Using Radial Basis Functions.
IEEE Computer Graphics and Applications.
1998.

Motion synthesis by interpolation of example motions. Example
motions of one kind (e.g. walk) but with a different
style (e.g. happy, downhill) are recorded and
parametrized by hand, i.e. a corresponding vector which components
are values of happiness, slope, etc. is specified. To synthesize
a new motion corresponding to a given parameter vector all DOFs
of example motions are interpolated by linear and radial basis
functions (scattered interpolation of irregular data). Parameter
vector can vary over time as well as transitions between different
kinds of motions are possible forming a motion graph. The realistic
interpolated motion if generated in realtime.

Artist-Directed Inverse-Kinematics Using
Radial Basis Function Interpolation.
Computer Graphics Forum (EUROGRAPHICS).
2001.

Inverse kinematics by interpolation of examples. Scattered example
poses are interpolated by radial basis functions. RBF interpolation
is improved comparing to paper Verbs & Adverbs of the same
authors. Weights for linear combination of examples as a whole are
computed using RBF against separate interpolation of DOF's curve
control points in Verb & Adverbs. Further techniques are
proposed to compensate serious inaccuracies of the used kind of
RBF interpolation.

Scattered Data Interpolation in Three or More
Variables.
Mathematical Methods in Computer Aided Geometric
Design.
1989.

A survey on scattered data interpolation in higher dimensions. The
most useful to motion interpolation seemes to be the point schemes
(Shepard's and radial basis) as they do not require a tesselation
of the multidimensional space.

Motion Capture Data Manipulation and Reuse via
B-splines.
Lecture Notes in Computer Science.
1998.

A non-uniform B-spline curve is fitted to each DOF of MC data by
least squares first. Then by curve manipulations simple operations
on the motion are performed yielding naive motion
blending/interpolation.

An Integrated Approach Towards the Representation,
Manipulation and Reuse of Pre-recorded Motion.
CA.
2000.

MC data are filtered and fitted by a non-uniform B-spline for each
DOF. Simple heuristics for a knot vector are proposed. Some usual
operations (path editing, motion warping, interpolation and
exaggerations) are performed on motion sequences in B-spline
functional representation by a simple naive way.

Realistic Synthesis of Novel Human Movements from
a Database of Motion Capture Examples.
Workshop on Human Motion.
2000.

Construction of a motion between given two keyframes using a
motion database. Body poses from example motions are quantized
(by clustering) and a Markov chain is build as well as Hidden
Markov model with motion examples in database as hidden states.
A new motion is synthesized by finding a path through Markov
chain states and using HMM to find corresponding parts of example
motion sequences.

Style Machines.
Computer Graphics (SIGGRAPH).
2000.

A generic model of a motion (as a state machine) and stylistic
degrees of freedom are found from examples of the motion in
different styles. That all is accomplished in a fully automatic
way by methods of learning (hidden Markov models, cross-entropy
minimization, annealing). No manual segmentation, alignment or
annotation is needed. The motion can be then resynthesized for
any value of a style variable

**v**. Results are very strong and applicable, e.g. altering the style of a choreography, enhancing the style of an unskilled performer, exaggeration, motion analogies or creation of a new complex and valid choreography.
Combined Partial Motion Clips.
Proceedings of WSCG.
2002.

Motion of a body part is added to a full body motion. The
partial motion doesn't just overlay a subset of body DOFs'
trajectories but affects possibly the entire motion. The
partial motion is extracted as a difference of a base motion
with and without a desired action. The extracted motions
across various bases are collected and non-zero DOFs are
identified. Each DOF with a small variance across the
partial motions is averaged, the other ones are stored for
each base motion. In motion synthesis the partial motion is
added to a base motion.

A drawback: The implementation of the proposed method is strongly dependent on a human assistance and decisions made by observations. A more automatic and general variation of the method is needed.

A drawback: The implementation of the proposed method is strongly dependent on a human assistance and decisions made by observations. A more automatic and general variation of the method is needed.

Generating Consistent Motion Transition via
Decoupled Framesapce Interpolation.
Computer Graphics Forum (EUROGRAPHICS).
2000.

Interpolation of cyclic motions. A sequence of significant events
(e.g. foot strikes or arm swing extremities) and their respective
normalized keytimes is (semiautomatically?) built for each source
clip. Then a linear (for 2 source clips) or bilinear (for 4
source clips) interpolation is performed using the time warped
by keytimes of events. The keytimes are interpolated first and
a relative time in an interval between successive events is
computed. The source motions are evaluated using the relative
time in interpolation. Moreover the upper and lower body halves
are decoupled – interpolated separately and their
coordination is smoothly corrected... Not so clearly explained.

Constrained Framespace Interpolation.
Computer Animation, Seoul.
2001.

Improved previous paper.
Interpolation of 2 or 4 motion sequences weighted by a user
specified B-spline curve. Keytimes – times of important events
in the motion sequence (e.g. end-effector interactions with
environment or joint angle extremities) are (semi?)automatically
identified and matched among example motions. The time is warped
then to interpolate the keytimes consistently. Interpolated pairs
or quadruples of motions sharing at least one cyclic motion may be
chained. Time warping is used as a common technique to synchronize
between upper and lower body timing or adjustments at joints
between successive example motions. Slight feet sliding is corrected
by IK. Application of the method for motion cyclifiaction is proposed.

FootSee: an Interactive Animation System.
Symposium on Computer Animation.
2003.

Synthesis of motion controlled by stepping on a pressure sensor
pad and using a motion library. Realtime, but with 1 second lag.
Simple analytic IK.

Footskate Cleanup for Motion Capture Editing.
Symposium on Computer Animation.
2002.

Fixing of skating feet in a walking motion. Analytic IK and smooth
blending of corrections to the original motion is used.

Interactive Control of Avatars Animated with
Human Motion Data.
.Computer Graphics (SIGGRAPH)
2002.

Human motion synthesis using a database of motion captured, unlabeled
motions. The database is preprocessed – all possible transitions
with a respective probability are assigned to each frame thus forming
a statistical (Markov) model. Another higher level model is constructed
by clustering for efficient search in the graph.

Only the original captured motions from the database can be applied to an avatar, the motions are not modified in any way.

Nice, structured bibliography of related papers.

Only the original captured motions from the database can be applied to an avatar, the motions are not modified in any way.

Nice, structured bibliography of related papers.

From Footprints to Animation.
Computer Graphics Forum (EUROGRAPHICS).
1997.

Motion synthesis from a given footprints sequence and their
respective timing information. The motion is generated in a
physics-based manner with a comfort term. Trajectory of a centre
of mass is found by global optimization. The leg poses are determined
then by IK. The method provides valuable anticipation and recovery
in the produced motion and runs in interactive rates.

Shape by Example.
Symposium on Interactive 3D Graphics.
2001.

Multidimensional interpolation of shapes using radial basis functions.
Also reparametrization of the abstract parameter space by inserting of
pseudoexamples is treated to prevent fatal deformation and cracks in
the shape.

Motion capture assisted animation: Texturing and
synthesis.
Proceedings of ACM SIGGRAPH '02.
2002.

**Update:**20. 10. 2004