11th Pacific Conference onComputer Graphics and Applications, 2003. Proceedings.
Many popular motion editing methods do not take physical principles into account potentially prod... more Many popular motion editing methods do not take physical principles into account potentially producing implausible motions. This paper introduces an efficient method for touching up edited motions to improve physical plausibility. We start by estimating a mass distribution consistent with reference motions known to be physically correct. The edited motion is then divided into ground and flight stages and adjusted to enforce appropriate physical laws for, respectively, zero moment point (ZMP) constraints and correct ballistic trajectory. Unlike previous methods, we do not solve a nonlinear optimization to calculate the adjustment. Instead, closed-form methods are used to construct a hierarchical displacement map which sequentially refines userspecified degrees of freedom at different scales. This is combined with standard methods for kinematic constraint enforcement, yielding an efficient and scalable editing method that allows users to model real human behaviors. The potential of our approach is demonstrated in a number of examples.
According to the principles of traditional 2D animation techniques, anticipation makes an animati... more According to the principles of traditional 2D animation techniques, anticipation makes an animation convincing and expressive. In this paper, we present a method to generate anticipation effects for an existing animation. The proposed method is based on the visual characteristics of anticipation, that is, "Before we go one way, first we go the other way [1]." We first analyze the rotation of each joint and the movement of the center of mass during a given action, where the anticipation effects are added. Reversing the directions of rotation and translation, we can obtain an initially guessed anticipatory pose. By means of a nonlinear optimization technique, we can obtain a consequent anticipatory pose to place the center of mass at a proper location. Finally, we can generate the anticipation effects by compositing the anticipatory pose with a given action, while considering the continuity at junction and preserving the high frequency components of the given action. Experimental results show that the proposed method can produce the anticipatory pose successfully and quickly, and generate convincing and expressive anticipation effects.
Proceedings of the 2002 ACM SIGGRAPH/Eurographics symposium on Computer animation, 2002
Locomotion such as walking, jogging, and running is one of the most basic forms of daily human mo... more Locomotion such as walking, jogging, and running is one of the most basic forms of daily human motions. However, the previous methods can hardly generate the convincing locomotion of a character following a curved path with a desired speed and style. Based on scattered data interpolation, we propose a novel approach for on-the-fly generation of convincing locomotion, given parameters such as speed, turning angle, and style, on top of others given in the previous approaches. We first present an incremental scheme for timewarping to align the example motion clips of various speeds. Then, we provide a novel scheme for joint angle blending which guarantees similar poses to have similar representations. Finally, we show how to adapt the blended motion to the target character and the environment in an on-line, real-time manner. The resulting motions are not only convincing but also effectively controlled to reflect animator's intention. Our approach is efficient enough for on-line applications such as real-time animation systems and video games.
Wire curve [15] is a simple, intuitive interface to local deformation of complex geometric object... more Wire curve [15] is a simple, intuitive interface to local deformation of complex geometric objects such as human face models. In this paper, we provide a formulation to extract wire curves and deformation parameters from a facial model based on the displacements of its vertices from those of the corresponding reference model. This extraction process is an inverse process of the wire deformation. With a mild assumption and interactive guide for setting the reference curves and their attributes, we show that the inverse process can be nicely formulated as an over-constrained system of linear equations that can be solved with a least squares minimization technique. We apply the extraction process to multiple face models with different types of expressions to obtain their corresponding wire curves. For facial animation, we blend those extracted wire curves and deformation parameters to finally deform the reference face model. Our proposed scheme facilitates both local deformation and non-uniform blending by making use of the power of wire deformation.
This paper proposes a methodology that allows users to control character's motion interactive... more This paper proposes a methodology that allows users to control character's motion interactively but continuously. Inspired by the work of Gleicher et al. (GSKJ03), we propose a semi-automatic method to build fat graphs where a node corresponds to a pose and its incoming and outgoing edges represent the motion segments starting from and ending at similar poses. A group of
... Advances in graphics hardware and rendering software have made it possible to build visually ... more ... Advances in graphics hardware and rendering software have made it possible to build visually rich virtual worlds, creating possibili-ties for entertainment ... A corpus of motion capture data is processed into a set of short clips that can be snapped together (concatenated) into ...
Computer puppetry maps the movements of a performer to an animated character in real-time. In thi... more Computer puppetry maps the movements of a performer to an animated character in real-time. In this article, we provide a comprehensive solution to the problem of transferring the observations of the motion capture sensors to an animated character whose size and proportion may be different from the performer's. Our goal is to map as many of the important aspects of the motion to the target character as possible, while meeting the online, real-time demands of computer puppetry. We adopt a Kalman filter scheme that addresses motion capture noise issues in this setting. We provide the notion of dynamic importance of an end-effector that allows us to determine what aspects of the performance must be kept in the resulting motion. We introduce a novel inverse kinematics solver that realizes these important aspects within tight real-time constraints. Our approach is demonstrated by its application to broadcast television performances.
11th Pacific Conference onComputer Graphics and Applications, 2003. Proceedings.
Many popular motion editing methods do not take physical principles into account potentially prod... more Many popular motion editing methods do not take physical principles into account potentially producing implausible motions. This paper introduces an efficient method for touching up edited motions to improve physical plausibility. We start by estimating a mass distribution consistent with reference motions known to be physically correct. The edited motion is then divided into ground and flight stages and adjusted to enforce appropriate physical laws for, respectively, zero moment point (ZMP) constraints and correct ballistic trajectory. Unlike previous methods, we do not solve a nonlinear optimization to calculate the adjustment. Instead, closed-form methods are used to construct a hierarchical displacement map which sequentially refines userspecified degrees of freedom at different scales. This is combined with standard methods for kinematic constraint enforcement, yielding an efficient and scalable editing method that allows users to model real human behaviors. The potential of our approach is demonstrated in a number of examples.
According to the principles of traditional 2D animation techniques, anticipation makes an animati... more According to the principles of traditional 2D animation techniques, anticipation makes an animation convincing and expressive. In this paper, we present a method to generate anticipation effects for an existing animation. The proposed method is based on the visual characteristics of anticipation, that is, "Before we go one way, first we go the other way [1]." We first analyze the rotation of each joint and the movement of the center of mass during a given action, where the anticipation effects are added. Reversing the directions of rotation and translation, we can obtain an initially guessed anticipatory pose. By means of a nonlinear optimization technique, we can obtain a consequent anticipatory pose to place the center of mass at a proper location. Finally, we can generate the anticipation effects by compositing the anticipatory pose with a given action, while considering the continuity at junction and preserving the high frequency components of the given action. Experimental results show that the proposed method can produce the anticipatory pose successfully and quickly, and generate convincing and expressive anticipation effects.
Proceedings of the 2002 ACM SIGGRAPH/Eurographics symposium on Computer animation, 2002
Locomotion such as walking, jogging, and running is one of the most basic forms of daily human mo... more Locomotion such as walking, jogging, and running is one of the most basic forms of daily human motions. However, the previous methods can hardly generate the convincing locomotion of a character following a curved path with a desired speed and style. Based on scattered data interpolation, we propose a novel approach for on-the-fly generation of convincing locomotion, given parameters such as speed, turning angle, and style, on top of others given in the previous approaches. We first present an incremental scheme for timewarping to align the example motion clips of various speeds. Then, we provide a novel scheme for joint angle blending which guarantees similar poses to have similar representations. Finally, we show how to adapt the blended motion to the target character and the environment in an on-line, real-time manner. The resulting motions are not only convincing but also effectively controlled to reflect animator's intention. Our approach is efficient enough for on-line applications such as real-time animation systems and video games.
Wire curve [15] is a simple, intuitive interface to local deformation of complex geometric object... more Wire curve [15] is a simple, intuitive interface to local deformation of complex geometric objects such as human face models. In this paper, we provide a formulation to extract wire curves and deformation parameters from a facial model based on the displacements of its vertices from those of the corresponding reference model. This extraction process is an inverse process of the wire deformation. With a mild assumption and interactive guide for setting the reference curves and their attributes, we show that the inverse process can be nicely formulated as an over-constrained system of linear equations that can be solved with a least squares minimization technique. We apply the extraction process to multiple face models with different types of expressions to obtain their corresponding wire curves. For facial animation, we blend those extracted wire curves and deformation parameters to finally deform the reference face model. Our proposed scheme facilitates both local deformation and non-uniform blending by making use of the power of wire deformation.
This paper proposes a methodology that allows users to control character's motion interactive... more This paper proposes a methodology that allows users to control character's motion interactively but continuously. Inspired by the work of Gleicher et al. (GSKJ03), we propose a semi-automatic method to build fat graphs where a node corresponds to a pose and its incoming and outgoing edges represent the motion segments starting from and ending at similar poses. A group of
... Advances in graphics hardware and rendering software have made it possible to build visually ... more ... Advances in graphics hardware and rendering software have made it possible to build visually rich virtual worlds, creating possibili-ties for entertainment ... A corpus of motion capture data is processed into a set of short clips that can be snapped together (concatenated) into ...
Computer puppetry maps the movements of a performer to an animated character in real-time. In thi... more Computer puppetry maps the movements of a performer to an animated character in real-time. In this article, we provide a comprehensive solution to the problem of transferring the observations of the motion capture sensors to an animated character whose size and proportion may be different from the performer's. Our goal is to map as many of the important aspects of the motion to the target character as possible, while meeting the online, real-time demands of computer puppetry. We adopt a Kalman filter scheme that addresses motion capture noise issues in this setting. We provide the notion of dynamic importance of an end-effector that allows us to determine what aspects of the performance must be kept in the resulting motion. We introduce a novel inverse kinematics solver that realizes these important aspects within tight real-time constraints. Our approach is demonstrated by its application to broadcast television performances.
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Papers by Hyun Joon Shin