Katsuaki Kawachi

An actuated physical puppet as an input device for controlling a digital manikin

We present an actuated handheld puppet system for controlling the posture of a virtual character. Physical puppet devices have been used in the past to intuitively control character posture. In our research, an actuator is added to each joint of such an input device to provide physical feedback to the user. This enhancement offers many benefits. First, the user can upload pre-defined postures to the device to save time. Second, the system is capable of dynamically adjusting joint stiffness to counteract gravity, while allowing control to be maintained with relatively little force. Third, the system supports natural human body behaviors, such as whole-body reaching and joint coupling. This paper describes the user interface and implementation of the proposed technique and reports the results of expert evaluation. We also conducted two user studies to evaluate the effectiveness of our method.

Hand Link Modeling and Motion Generation from Motion Capture Data Based on 3D Joint Kinematics

Characterization of the human hand motion necessary to manipulate hand-held equipment requires accurate capture and reconstruction of the arbitrary subjects hand motions with respect to the object. The present study used an individual link structure modeled from optical motion capture data to perform this task and compared the results against those obtained by medical imaging. Posture data was captured while grasping several cylinders, and the captured data were utilized to generate new postures to grasp cylinders of arbitrary diameter.

Functional Shoulder Joint Modeling for Accurate Reach Envelopes Based on Kinematic Estimation of the Rotation Center

We developed a new method to estimate the functional center of rotation of the shoulder joint. Using this method, we examined the relationship between the posture of the upper arm and the displacements of the estimated center of rotation of the shoulder joint. The displacements were calculated from the flexion-extension angle and abduction-adduction angle of the upper arm. In this study, we propose a shoulder model for digital manikins that simulates reach envelopes more accurately than that for the existing digital manikins.

A lightweight algorithm for real-time motion synthesis

This paper presents an algorithm for interactive character animation with kinematic constraints with limited computational time. In order to reduce necessary computation, the animation is not created by procedural algorithm but synthesized by deforming and concatenating short motion examples, each consisting of a sequence of postures. A keyframe placed between two consecutive motion examples is deformed by using inverse kinematics so that it satisfies given constraints. The motion examples between the keyframes are deformed to ensure continuity of postures in position and velocity. We parameterize each posture as a set of particles in an orthogonal coordinate system. The inverse kinematics method with the particle representation realizes fast and stable deformation of keyframe postures, and the deformation of motion examples are calculated on a frame-by-frame basis by decomposing a whole-body deformation into per-particle deformations. We present some examples of character animations synthesized at an interactive rate by this algorithm.