Tsuneya Kurihara

A simple method for extracting the natural beauty of hair

A simple differential equation method is proposed for modeling the aesthetic features of human hair. In the method, a simplified cantilever beam simulation is employed for hairstyle modeling, which allows hairdressing variations with volumetric and realistic appearance. In order to describe the dynamical behavior of hair in an animation, one-dimensional projective differential equations of angular momenta for linked rigid sticks are also derived. For the problem of collision detection between hair and a human head, the “rough” approximate solution is provided, which gives visually satisfactory results by solving the projective equations under a ps~udo-force field. The hair’s pliability can be controlled by using a set of stiffness parameters in the method. In addition, a fast rendering technique for anisotropic reflection is introduced, which is derived from Blirm’s specular model. The efficiency of the proposed method is illustrated by the still images and short animations obtained. CR

An Integrated System for Modeling, Animating and Rendering Hair

There are basically four problems to solve in order to produce realistic animated synthetic actors with hair: hair modeling and creation, hair motion, collision detection and hair rendering. This paper describes a complete methodology to solve these basic four problems. We present how hair styles may be designed with our Hair Styler module. Then we survey the animation model and emphasize a method of collision processing. Finally, we explain how hair may be rendered using an extension of a standard ray‐tracing program. We also show applications of our synthetic actors with various hair styles and different styles of mustaches and beards.

Modeling deformable human hands from medical images

This paper presents a new method for constructing an example-based deformable human hand model from medical images. Realistic animation of human hands requires good estimates of the joint structure and properly weighted skeleton-driven surface deformation. For this purpose, we propose a method based on medical images of hands in several poses. Our method consists of the following 3 steps: First, using the measured bone shapes, we estimate the link structure (joint rotation centers) and the joint angles of each scan. Second, we construct a mutually consistent polygonal mesh of all the scans. For this purpose, a polygonal mesh of one pose, the base mesh, is deformed using skeletal subspace deformation, and then fitted interactively to the measured meshes from the other scans. Finally, the hand is deformed using a weighted pose space deformation. We demonstrate results of deformable hand models consisting of 100,000 triangle meshes derived from CT scans.

A Transformation Method for Modeling and Animation of the Human Face from Photographs

This paper describes a new transformation method for modeling and animation of the human face. A 3-D canonical facial model is introduced which is transformed to a facial model that is consistent with photographs of an individual face. Facial expression is modified by transformation of the obtained facial model. By using the displacements of selected control points, the transformation determines the displacements of the remaining points by linear interpolation in a 2-D parameter space. To generate texturemapped facial images, photographs are first projected onto a 2-D space using cylindrical coordinates and then combined, taking into account their positional certainty.

Modeling of human hand link structure from optical motion capture data

This paper proposes the total protocol to determine the link structure of a human hand using optical motion capture data. The difficulty in capturing hand motion comes from the hands relatively high degrees of freedom located in very small space. To deal with the problem caused by closeness between markers, the number of markers is reduced. The effect of reduced markers is compensated by simplifying the problem. The adverse effect of skin movement and the limited range of movement is avoided by regulating the calibration motion appropriately. A link estimation experiment is performed to show the effectiveness of the proposed method.

Hair animation with collision detection

We propose an efficient method for hair animation. The movement of hairs is modeled by simplified physical simulations. In particular the method can treat successfully collisions between hair and a human body or other objects, which provides realistic hair animation. The fast collision detection is achieved using cylindrical representation of the head and human body parts, despite a large number of hairs. The cylindrical representation allows collision detection to be performed by table look-up and interpolation, which assures that the computation time is independent of the complexity of the objects. A reaction constraint algorithm is also applied for the collision reaction to simulate inelastic contact. The efficiency of the method is well illustrated by the animation obtained.

Bilinear interpolation for facial expression and metamorphosis in real-time animation

This paper describes a new method for generating facial animation in which facial expression and shape can be changed simultaneously in real time. A 2D parameter space independent of facial shape is defined, on which facial expressions are superimposed so that the expressions can be applied to various facial shapes. A facial model is transformed by a bilinear interpolation, which enables a rapid change in facial expression with metamorphosis. The practical efficiency of this method has been demonstrated by a real-time animation system based on this method in live theater.

Finger joint kinematics from MR images

Accurate and quantitative analysis of human hand motion requires an understanding of the kinematics of the proximal and distal interphalangeal joints in three dimensions. This paper presents a technique to investigate in-vivo finger joint kinematics using magnetic resonance (MR) imaging. Bone surface models were extracted from MR images of the right hand of ten healthy subjects in four different postures. The relative motion of adjacent bones for all subjects was calculated and expressed as the helical axis and the angles around the axes of local bone coordinate system. The motion data indicated the change of axis orientation with flexion. After carefully selecting the subject and a pose with an appropriate flexional angle, studies determined that the mean inclination between the axes of the proximal and distal interphalangeal joints was approximately 14 [deg].

GPU-based fast pencil beam algorithm for proton therapy

Performance of a treatment planning system is an essential factor in making sophisticated plans. The dose calculation is a major time-consuming process in planning operations. The standard algorithm for proton dose calculations is the pencil beam algorithm which produces relatively accurate results, but is time consuming. In order to shorten the computational time, we have developed a GPU (graphics processing unit)-based pencil beam algorithm. We have implemented this algorithm and calculated dose distributions in the case of a water phantom. The results were compared to those obtained by a traditional method with respect to the computational time and discrepancy between the two methods. The new algorithm shows 5-20 times faster performance using the NVIDIA GeForce GTX 480 card in comparison with the Intel Core-i7 920 processor. The maximum discrepancy of the dose distribution is within 0.2%. Our results show that GPUs are effective for proton dose calculations.

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.