Towards adaptive and directable control of simulated creatures

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 71-77).Interactive animation is used ubiquitously for entertainment and for the communication of ideas. Active creatures, such as humans, robots, and animals, are often at the heart of such animation and are required to interact in compelling and lifelike ways with their virtual environment. Physical simulation handles such interaction correctly, with a principled approach that adapts easily to different circumstances, changing environments, and unexpected disturbances. However, developing robust control strategies that result in natural motion of active creatures within physical simulation has proved to be a difficult problem. To address this issue, a new and versatile algorithm for the low-level control of animated characters has been developed and tested. It simplifies the process of creating control strategies by automatically accounting for many parameters of the simulation, including the physical properties of the creature and the contact forces between the creature and the virtual environment. This thesis describes two versions of the algorithm (one fast and one feature-rich) and the experiments conducted to evaluate its performance.(cont.) The results include interactive animations of active creatures manipulating objects and balancing in response to significant disturbances from their virtual environment. The algorithm is shown to be directable, adaptive, and fast and to hold promise for a new generation of interactive simulations that feature lifelike creatures acting with the same fluidity and grace exhibited by natural beings.by Yeuhi Abe.S.M

A phase-indexed tracking controller for interactive physical simulation of animated characters

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 103-107).In this thesis, I describe a method of animating characters using physical simulation. The main advantage of this approach, verses traditional keyframing methods, is that the animated character can react to physical interactions. These reactions can be synthesized in real-time in interactive applications, such as video games, where traditional approaches can only playback pre-recorded sequences. Physically simulating a character requires a controller, but creating a controller is known to be a challenging task, especially when animation concerns about the style of the motion are taken into consideration. This thesis describes a method of generating a controller automatically and quickly from an input motion. The stylistic aspects of the controller are particularly easy to control, as they are a direct result of the input motion. In order to generate a controller from an input motion, I address two main challenges. First, the input motion must be rectified (minimally modified) to ensure that it is physically plausible. Second, a feedback strategy must be formulated to generate control forces during the simulation. The motion rectification problem is addressed by formulating a fast trajectory optimization that solves for a reference motion. The reference minimally deviates from the input motion to satisfy physical constraints. The second challenge is addressed by employing a novel phase-indexed controller that uses a combination of local and global feedback strategies to keep the character tracking the reference motion. Beyond tracking just a single reference motion, I also demonstrate how variation to a input motion can be automatically synthesized using the same trajectory optimization method used in the rectification process, and how these variations can be sequenced, using optimal control, to accomplish various goals.by Yeuhi Abe.Ph.D

Interactive simulation of stylized human locomotion

Animating natural human motion in dynamic environments is difficult because of complex geometric and physical interactions. Simulation provides an automatic solution to parts of this problem, but it needs control systems to produce lifelike motions. This paper describes the systematic computation of controllers that can reproduce a range of locomotion styles in interactive simulations. Given a reference motion that describes the desired style, a derived control system can reproduce that style in simulation and in new environments. Because it produces high-quality motions that are both geometrically and physically consistent with simulated surroundings, interactive animation systems could begin to use this approach along with more established kinematic methods.Singapore-MIT GAMBIT Game LabNational Science Foundation (U.S.) (Fellowship 2007043041)Pixar (Firm

Interactive Animation of Dynamic Manipulation

Lifelike animation of manipulation must account for the dynamicinteraction between animated characters, objects, and their environment. Failing to do so would ignore the often significant effects objectshave on the motion of the character. For example, lifting a heavy objectwould appear identical to lifting a light one. Physical simulationhandles such interaction correctly, with a principled approach thatadapts easily to different circumstances, changing environments, andunexpected disturbances. Our work shows how to control lifelike animatedcharacters so that they accomplish manipulation tasks within aninteractive physical simulation. Our new multi-task control algorithmsimplifies descriptions of manipulation by supporting prioritized goalsin both the joint space of the character and the task-space of theobject. The end result is a versatile algorithm that incorporatesrealistic force limits and recorded motion postures to portray lifelikemanipulation automatically

M.-P. Cani, J. O’Brien (Editors) Interactive Animation of Dynamic Manipulation

Lifelike animation of object manipulation requires dynamic interaction between animated characters, objects, and their environment. These interactions can be animated automatically with physically based simulations but proper controls are needed to animate characters that move realistically and that accomplish tasks in spite of unexpected disturbances. This paper describes an efficient control algorithm that generates realistic animations by incorporating motion data into task execution. The end result is a versatile system for interactive animation of dynamic manipulation tasks such as lifting, catching, and throwing

Momentum-based Parameterization of Dynamic Character Motion

This paper presents a system for rapid editing of highly dynamic motion capture data. At the heart of this system is an optimization algorithm that can transform the captured motion so that it satisfies high-level user constraints while enforcing that the linear and angular momentum of the motion remain physically plausible. Unlike most previous approaches to motion editing, our algorithm does not require pose specification or model reduction, and the user only need specify high-level changes to the input motion. To preserve the dynamic behavior of the input motion, we introduce a spline-based parameterization that matches the linear and angular momentum patterns of the motion capture data. Because our algorithm enables rapid convergence by presenting a good initial state of the optimization, the user can efficiently generate a large number of realistic motions from a single input motion. The algorith