Published papers

The liquid dynamics has a significant impact on video works, and bleeding is no exception. Hemorrhage scenes possess highly-important implications, as seen from the fact that they might make the work rated age limit. Lack of visual reality in those scenes would reduce the overall quality of the work. Against this background, we have built upon a commonly-used Lagrangian method, called SPH (Smoothed Particle Hydrodynamics), to simulate bleeding on skin surfaces more faithfully. Remarkable features of the extension are three-fold: (1) bleeding from a wound modeled along with in-vivo blood flow, which takes account of the wound’s shape, hemorrhage volume, and bleed momentum; (2) physisorption of blood on the skin surfaces formulated by introducing an additional adsorption term, analogous to van der Waals force, to the original Navier-Stokes equations and by allowing for saturation of adsorption media; and (3) congelation of blood represented by varying viscosity according to the time exposed to the air.

In this paper, we present an interactive approach to visual simulation of whirlwind using a grid and particles. High-resolution simulation can be carried out efficiently by perturbing air flow computed on a rough grid with small-scale turbulence. The grid-based simulation first provides a primary whirlwind flow field through modeling its underlying heat convection. Then, the particle-based simulation computes the transport energy of turbulence based on a two-equation k-ipsilon model, which allows us to capture the turbulence details. The dynamism of whirlwind is conveyed effectively by the interaction with rigid and deformable bodies, such as flag, branch and paper, placed on interactively-controllable trajectories. In addition, a simplified variant of particle-based volume rendering is utilized to delineate changes in the translucency of whirlwind, which reflects the amount of sand particles stirred up from the ground.

Rapid dissemination of DT-MRI devices has recently evoked intensive research to come up with effective methods for grasping the structural features of acquired 3D diffusion tensor fields. In this paper, we further explore the potential of haptization in conjunction with visualization to represent different levels of information on the DT-MRI datasets. The main contribution of this paper is to propose a sophisticated method for utilizing diffusion-based tractography textures mapped on cross-sections to visualize local structures such as nerve tracts, together with appropriate 6DOF haptic transfer functions to haptize elementary diffusion properties. We illustrate the effectiveness of a prototype system featuring a PHANToM Premium 3.0 with an application to a practical DT-MRI human brain dataset.

Volume datasets have been a primary representation for scientific visualization with the advent of rendering algorithms such as marching cubes and ray casting. Nonetheless, illuminating the underlying spatial structures still requires careful adjustment of visualization parameters each time when a different dataset is provided. This paper introduces a new framework, called feature-driven volume fairing, which transforms any 3D scalar field into a canonical form to be used as communication media of scientific volume data. The transformation is accomplished by first modulating the topological structure of the volume so that the associated isosurfaces never incur internal voids, and then geometrically elongating the significant feature regions over the range of scalar field values. This framework allows us to elucidate spatial structures in the volume instantly using a predefined set of visualization parameters, and further enables data compression of the volume with a smaller number of quantization levels for efficient data transmission.

The design of automatic transfer functions for volume rendering is a perennial problem in volume visualization. Over the last three decades, a variety of design methodologies have been proposed. However, sensitive adjustment of related control parameters remains entrusted to users, because rendering conditions,such as the thickness of emphasized subvolumes in the ray direction and the size of a target dataset, differ on a case-by-case basis. Our group previously proposed one-dimensional transfer functions to accentuate topological changes in the scalar field of the target dataset. However, the method forces us to determine the actual control parameter values for the transfer functions in an empirical manner. In this paper, we propose a supplementary mechanism with which to judiciously define an appropriate profile of the opacity values. More specifically, the height and width of the hat opacity transfer functions that accentuate feature isosurfaces are determined according to the number of voxels belonging to the relevant topologically equivalent scalar field interval. The feasibility of the proposed method is evaluated by its application to five kinds of volume datasets.

This study aims to effectively design an apparel item by converting a polygon model of the human body obtained through 3D scan into a volume model. From the model, we can quickly generate a curved surface that retains a constant distance from the body surface, and thus design clothing material that ensures accurate “allowance” by defining the distance field for the body surface. Furthermore, by drawing a design line on the curved surface, the pattern required for actual sewing can be designed in three dimensions. A dynamics simulation is applied to smooth the curvatures so that the desired flat surface pattern can finally be obtained. As a result of actually sewing the virtually designed pattern and try-on, it was proven that we can generate clothes with the appropriate allowance and proportions.

In 3D character animation, the frame rate is often reduced to mimic hand-drawn animations, like anime (Japanese animation). However, anime with a low frame rate differs from real motions because it omits excessive movements and emphasizes speed by expressing motions with a small number of impressive poses. It is difficult to reproduce such motions only by downsampling mocap data. Thus, in this poster, we propose a method for converting mocap data into anime-like 2D motions by respecting production site techniques. The proposed method evaluates the characteristics of motion data using the time distributions of speeds and pose areas to select an appropriate sequence of viewpoints and extract effective poses for each viewpoint.

Individuals with eye diseases that cause optic nerve damage, such as glaucoma, suffer from visual field defects (VFDs), rendering the assessment of VFDs an essential step in medical treatment. In existing studies, various methods have been proposed for VFD area inspections. However, these methods present several problems, including long inspection times and the need to maintain a posture for extended periods, potentially placing significant physical and psychological burdens on patients and affecting the accuracy of the inspection result. Moreover, loose eye fixation constraints also decrease the reliability of the result. In response, we herein propose a novel approach for a fast VFD test, facilitated by the quadtree algorithm. To overcome the physical burden caused by posture constraints related to the testing area requirements and location of the stimulus, the proposed VFD test is implemented on a head-mounted display with a built-in eye tracker. To improve the accuracy of the inspection result further, variously sized noise fields were adopted as the stimuli shown to the examinees. In addition, to validate the performance of the proposed method, a mock experiment was conducted in this study, which involved volunteers with normal vision. The experimental results indicate that the proposed method demonstrates a competitive advantage in perimetric time compared to current state-of-the-art methods, and it exhibits advantages in terms of both accuracy and user comfort.

XR技術の発展に伴い，撮影動画からの三次元(3D)シーン再構成に対する需要が高まってきている．Neural Radiance Fieldsの登場を皮切りに，3D再構成に関する研究は急速な発展を遂げ，スマートフォンでも簡単に3D再構成ができる環境となりつつある．その一方で，シーンや特定のオブジェクトに対する編集は難しく，未だ途上段階である．そこで本研究は，Gaussian Splattingにより再構成された3Dシーンの自動的な編集を目指す．特に本論文では，シーンの前景部分を濃縮するボリュームシームカービングの手法を提案する．提案手法では，3D Gaussianシーンをボクセルグリッドに変換し，マルチパス動的計画法によるエネルギ最小化に基づくシーム面抽出を繰り返し適用することで，各ガウシアンの幾何的・外観的特徴および空間的一貫性を反映しながら，不要な前景領域を削除し，シーンを濃縮する．異なるシーンに適用し，シーン全体の主要な外観的特徴を維持した前景濃縮の実現性を示すことで，本手法が再構成3Dシーンの自動編集に向けた実用的アプローチであることを実証する．フルペーパー．松本は学生奨励賞受賞．