1. Layered Acting for Character Animation By Mira Dontcheva Gary Yngve Zoran Popović presented by Danny House SIGGRAPH 2003

2. Editing Motion Keyframing: positions and tangents Physical Simulation: initial conditions Motion Graphs: splicing Texturing

3. Layered Editing Start with Broad Outline Top Down Construction

4. Dimensions for Layering Accuracy Scale Articulation

5. Layers of Articulated Movement Torso Limbs to Fingers Head to Face to Eyes Secondary Motion

6. Interaction via Acting Correspondence of Movement and Time Not Quite Puppetry Motion Capture

7. Imitation Imitating the User Imitating the Animated Character

8. System Overview Hardware Space and Time Interaction Character Interaction Synthesis and Editing With Layers

9. Hardware 8 camera optical motion capture wireless mouse wall display screen various animation widgets

10. Space and Time Interaction Camera View and Studio Correspondence Distance to Object Affects Gain on Controls Ground Calibration Speed and Interval of Playback Anticipation Guides –Predictive Ghost Renderings –Projections of Trajectory Streamers

11. Character Interaction User Features –position and orientation of widgets Character Features Correspondence Between Character and User Features

12. Character Features Must be prespecified in the character model. May include –joints –points on the body –DOFs –IK handles

13. Correspondence Between Character and User Features Explicit selection by User Implicit selection via acting Absolute, trajectory-relative, or additive

14. Synthesis and Editing with Layers Select One or More Character Features Map them to a Widget Act with the Widget while Watching Playback Repeat

15. Definitions for Feature Mapping X 0 : initial position of widget X(t): position of widget at time t C´: rotational component of transform from studio to camara coordinates Y 0 : initial position of character feature Y(t): position of character feature at time t Y ´(t): character feature’s position after edit X R 0, X R (t), etc, are the corresponding rotations

16. Absolute Feature Mapping Used for top level rough sketch of motion Good for contact with ground –the system supports snapping to the ground Useful for body parts that interact with in the scene Could be useful with physical props

17. Equations of Absolute Feature Mapping Y ´(t) = Y 0 + C´(X(t) - X 0 ) Y R ´(t) = C´X R (t)(X R 0 ) -1 Y R 0

18. Trajectory-Relative Mapping Useful for animating a feature relative to an existing parent motion. K(t) is the product of the matrices in the parent hierarchy of the feature being edited. Y ´(t) = Y 0 + K(t)C´(X(t) - X 0 )

19. Additive Mapping Useful for adding detail or personality while preserving the underlying motion Y ´(t) = Y(t) + C´(X(t) - X(t-dt))

20. Equations of Trajectory-Relative Mapping K(t) is the change in the widget’s translation over [0,t] Y ´(t) = Y 0 + K(t)C´(X(t) - X 0 )

21. Implicit Editing The user selects the features to edit by imitating their behavior. The system discovers the relevant features using a statistical technique called “Canonical Correlation Analysis” or CCA. CCA is applied to each user/character feature pair. Heuristics are used to choose the best pairs. They are non-robust but effective in practice.

22. Physically Based Motion Transformation By Popović, Z. and Witkin, A. P. SIGGRAPH 99 Sophisticated retargeting of motion data.

23. Preparation for Editing Character Simplification –manual elimination of many details Spacetime Motion Fitting –manual capture of pose and mechanical constraints, addition of muscles, assumes optimality

24. Editing Tweak the Constraints –change a pose, alter flexibility of a joint, introduce obstacles, alter gravity Motion Reconstruction –automtic

25. Interactive Manipulation of Rigid Body Simulations Popović, J., Seitz, S. M., Erdmann, M., Popović, Z., and Witkin, A. P. SIGGRAPH 2000 Allows goal oriented editing of physical simulations.

26. User specifies waypoints and velocities in simulation. Will alter initial conditions if permitted. Obtains extra DOFs by tweaking surface normals, elasticity. Small changes in these parameters are not noticed by audience.