Ari Shapiro

Hybrid control for interactive character animation

We implement a framework for animating interactive characters by combining kinematic animation with physical simulation. The combination of animation techniques allows the characters to exploit the advantages of each technique. For example, characters can perform natural-looking kinematic gaits and react dynamically to unexpected situations. Kinematic techniques such as those based on motion capture data can create very natural-looking animation. However, motion capture based techniques are not suitable for modeling the complex interactions between dynamically interacting characters. Physical simulation, on the other hand, is well suited for such tasks. Our work develops kinematic and dynamic controllers and transition methods between the two control methods for interactive character animation. In addition, we utilize the motion graph technique to develop complex kinematic animation from shorter motion clips as a method of kinematic control.

Chemoprevention of prostate cancer with lycopene in the TRAMP model.

Dietary lycopene combined with other constituents from whole tomatoes was previously found to have greater chemopreventive effects against prostate cancer as compared to pure lycopene provided in a beadlet formulation. We hypothesized that tomato paste would have greater chemopreventive effects in transgenic adenocarcinoma of the mouse prostate (TRAMP) mice relative to equivalent lycopene doses provided from lycopene beadlets.

On the beat!: timing and tension for dynamic characters

Dynamic simulation is a promising complement to kinematic motion synthesis, particularly in cases where simulated characters need to respond to unpredictable interactions. Moving beyond simple rag-doll effects, though, requires dynamic control. The main issue with dynamic control is that there are no standardized techniques that allow an animator to precisely specify the timing of the motion while still providing natural response to external disturbances. The few proposed techniques that address this problem are based on heuristically or manually tuning proportional-derivative (PD) control parameters and do not generalize easily. We propose an approach to dynamic character control that is able to honor timing constraints, to provide natural-looking motion and to allow for realistic response to perturbations. Our approach uses traditional PD control to interpolate between key-frames. The key innovation is that the parameters of the PD controllers are computed for each joint analytically. By continuously updating these parameters over time, the controller is able to respond naturally to both external perturbations and changes in the state of the character.

A dynamic controller toolkit

We introduce a toolkit for creating dynamic controllers for articulated characters under physical simulation. Our toolkit allows users to create dynamic controllers for interactive or offline use through a combination of both visual and scripting tools. Users can design controllers by specifying keyframe poses, using a high-level scripting language, or by manipulating the rules of physics through a group of helper functions that can temporarily modify the environment in order to make the desired animation more feasible under physical simulation. The goal of the toolkit is to integrate dynamic control methods into a usable interactive system for noncomputer scientists and non-roboticists, and provide the means to quickly generate physically based motion.

Interactive and reactive dynamic control

We provide an interface for controlling humanoid characters under physical simulation. This interface permits a user to control the character at a variety of different semantic levels. The character can be instructed at a high level, such as by issuing a walk command, or at a low level, such as by specifying poses with interactive keyframe selection. In addition, the character can perform autonomously in that it possesses a variety of reactive skills that can be performed when needed. Our work brings together interactive control with reactive control under physical simulation as a major step towards a larger system for an intelligent, controllable and interactive character.

Interactive motion decomposition

Figure 1: In the left image the original walk (left actor) has been modified with a ”sneaky” style, yielding a sneaky walk (right actor). In the right image, the sneaking motion (left actor) is modified with a ”walking” style, yielding a walk-like sneak that appears as a tiptoeing motion (right actor). Our visual decomposition works with any sort of motion data, including motion captured and keyframed data.

Complex character animation that combines kinematic and dynamic control

We implement a framework for developing interactive characters by combining kinematic animation with physical simulation. The combination of animation techniques allows the characters to exploit the advantages of each technique. For example, characters can perform natural-looking kinematic gaits and react dynamically to unexpected situations. Kinematic techniques such as those based on motion capture data can create very natural-looking animation. However, motion capture based techniques are not suitable for modeling the complex interactions between dynamically interacting characters. Physical simulation, on the other hand, is well suited for such tasks. Our work develops kinematic and dynamic controllers for interactive character animation, leveraging the advantages of both classes of techniques.