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This article proposes a new discrete collision handling method (DCH method) that can be used for resolving tanglements in clothing simulation, based on the existing continuous collision handling methods (CCH methods). The proposed method performs intersection analysis of the clothing mesh at every time step, and stores the result in the form of coloring the vertices, edges, and triangles. Referring to the coloring, the method resolves the tanglements in the out-to-in manner by applying the proposed operations, the triangle shrinkage and vertex pull, to the triangles and vertices around the intersection path. We take note of the CCH methods that use some small tolerance value to defend the round-off errors for the purpose of preventing false negatives. This work gives a second thought to that tolerance value, and proposes a new DCH method which uses the tolerance value for the resolution purpose. Under certain conditions, the method turns out to guarantee resolution of the tanglements in a finite number of time steps.

This paper investigates the question of whether the Jacobi preconditioner can be made to run faster by including a few additional outlying diagonals, for the case of mesh-based implicit clothing simulation. For the given $$N \times N$$ block system matrix $${\mathbf {A}}$$ , we investigate two regularly striped (RS) preconditioners: (1) 3-RS which has two symmetric outlying diagonals with offset $$\frac{N}{2}$$ from the main diagonal and (2) 5-RS which has four symmetric outlying diagonals with offsets $$\frac{N}{3}$$ and $$\frac{2N}{3}$$ from the main diagonal. This paper finds that both 3- and 5-RS preconditioners are consistently superior to the Jacobi preconditioner in the performance. Based on the loop iteration count and time measurement, we finally recommend 5-RS rather than 3-RS.

Face recognition now requires a large number of labelled masked face images in the era of this unprecedented COVID-19 pandemic. Unfortunately, the rapid spread of the virus has left us little time to prepare for such dataset in the wild. To circumvent this issue, we present a 3D model-based approach called WearMask3D for augmenting face images of various poses to the masked face counterparts. Our method proceeds by first fitting a 3D morphable model on the input image, second overlaying the mask surface onto the face model and warping the respective mask texture, and last projecting the 3D mask back to 2D. The mask texture is adapted based on the brightness and resolution of the input image. By working in 3D, our method can produce more natural masked faces of diverse poses from a single mask texture. To compare precisely between different augmentation approaches, we have constructed a dataset comprising masked and unmasked faces with labels called MFW-mini. Experimental results demonstrate WearMask3D produces more realistic masked faces, and utilizing these images for training leads to state-of-the-art recognition accuracy for masked faces., Comment: 5 pages, 5 figures and 2 tables; accepted to ICIP 2021

Based on the physically-based clothing simulation, this paper develops a novel method to customize the fit of the given garment to the reference body. The method defines three misfit measures, namely the landmark point misfit, landmark line misfit, and circumferential misfit, based on the correspondence between the landmark points and landmark lines in the body and garment. In terms of the above misfit measures, this paper proposes the heuristic misfit reduction method. The heuristic misfit reduction method works in the following way. Starting from a given preliminary garment, it (1) performs the fit evaluation, (2) modifies the panels based on the evaluation to enhance the fit, then (3) performs the draping simulation with the modified panels. The procedure is repeated until a satisfactory fit is achieved. According to our experiments, the proposed method successfully customizes a given garment to fit to the given body.

In clothing design and manufacturing, the need to attach a foreground (such as an emblem or pocket) on the background (i.e., clothing surface) arises. For that, stitch forming line needs to be identified on the surface of the background that should be seamed with that of the foreground. Often, the shape of the background is non-developable thus the problem is not straightforward. In this paper we developed an optimization method to overlay the foreground on the background such that the planar deformation and the deformation variance of the foreground is minimized. We applied the optimization technique to various cases of developable and non-developable background cases and verified the optimization works as expected.

This paper proposes a new method that can be used when virtual ensembles need to be put on to a 3D avatar. We assume that input to the virtual fitting system is a number of garments draped on a target avatar. Then, the problem is to account for the interference between the garments and produce the scene in which the constituent garments are worn in an ensemble. For that, we propose a technique to stratify the garments such that they do not intersect in any region, thus the conventional simulators can start from a workable initial configuration. Then, we introduce the regional simulation omission, which can generate try-on of ensembles in a significantly reduced amount of time. Experiments show that, in the robustness, processing speed, and flexibility, the proposed method is strikingly better than the conventional approach.

의상 시뮬레이션과 렌더링 계산비용은 메쉬의 종류와 그 품질에 크게 좌우된다. 일반적으로 정확도와 효율성 면에서 삼각메쉬 보다 사각메쉬가 더 선호된다. 본 논문은 재귀 기하 분할법에 기초한 의복 패턴의 사각화 방법을 기술한다. 논문에서는 기존의 방법에서 두 가지 개선점을 제안한다. 첫째, 제안 방법은 기존의 방법보다 향상된 회귀 기하 분해 알고리즘을 사용한다. 제안된 방법에서 의복패턴의 물리적 도매인은 보다 더 간단하고 맵핑 가능한 형태로 분해된다. 둘째, 본 논문에서는 정점 분류 알고리즘의 유효성 확인작업을 수행한다. 제안 알고리즘을 이용하여 인식 되지 않은 정점 분류에 대한 유효성을 검증 할 수 있다.

This paper presents a new method which can create the virtual garment from a single photograph of a real garment put on to the mannequin. In solving this problem, we obtain the insight from the pattern drafting theory in the clothing field. We abstract the drafting process into a computer module, which takes the garment type and primary body sizes then produces the draft as the output. Then the problem is reduced to find out the garment type and primary body sizes. We find that information by analyzing the silhouette of the garment with respect to the mannequin. The method works robustly and produces practically usable virtual clothes that can be used for the graphical coordination. Copyright © 2015 John Wiley & Sons, Ltd.

We present a new technique which can handle both point and sliding constraints in the multigrid (MG) framework. Although the MG method can theoretically perform as fast as O(N), the development of a clothing simulator based on the MG method calls for solving an important technical challenge: handling the constraints. Resolving constrains has been difficult in MG because there has been no clear way to transfer the constraints existing in the finest level mesh to the coarser level meshes. This paper presents a new formulation based on soft constraints, which can coarsen the constraints defined in the finest level to the coarser levels. Experiments are performed which show that the proposed method can solve the linear system up to 4–9 times faster in comparison with the modified preconditioned conjugate gradient method (MPCG) without quality degradation. The proposed method is easy to implement and can be straightforwardly applied to existing clothing simulators which are based on implicit time integration.

We present a new framework to simulate moving interfaces in viscous incompressible two phase flows. The goal is to achieve both conservation of the fluid volume and a detailed reconstruction of the fluid surface. To these ends, we incorporate sub-grid refinement of the level set with the volume-of-fluid method. In the context of this refined level set grid we propose the algorithms needed for the coupling of the level set and the volume-of-fluid, which include techniques for computing volume, redistancing the level set, and handling surface tension. We report the experimental results produced with the proposed method via simulations of the two phase fluid phenomena such as air-cushioning and deforming large bubbles.

This paper presents a novel framework for garment grading. In CG, an extensive amount of study has been carried out to clothe human characters, but little attention has been taken to the grading problem itself. For the development of a grading technique, we obtained the insight from the process of drawing the patternmaking draft (sloper) in the clothing field. Noting that the draft can be completely determined by supplying the primary body sizes, we abstract the draft construction process as a computer procedure, which we call the parametrized draft. With the parametrized draft, we develop a grading method based on the draft-space warping, which takes three steps: (i) draft-space encoding, (ii) target draft construction, then (iii) draft-space decoding. The proposed grading method can be performed instantly for any given body without calling for the user's intervention. With experimental results, we show that the new grading framework can bring an improvement to garment grading. Copyright © 2013 John Wiley & Sons, Ltd.

*IT technology has been rapidly introduced to the clothing and fashion industry, and especially fashion shows have been changed very fast to keep up with the current digital era. In this research, the author designed virtual clothes, and investigated whether it is possible to make them similar to actual clothes and then performed a digital fashion show with these virtual clothes. This research discussed, based on case development and studies, whether a digital fashion show can express the designer`s idea more creatively than the existing fashion shows and what needs to be improved for the effectiveness of digital fashion shows. As a result, the virtual clothes have been recognized to be very similar to actual clothes and facilitate creative expressions that are hard to be presented in actual fashion shows. The adaptation of 3D virtual clothes to real fashion industry in the future can make new contents through the innovation of distribution and industry.

A new technology of fashion show is opening the digital era and an imaginary fashion show is now arising as a new form of fashion show which allows one to enjoy a collection through the monitor without holding a real fashion show. Digital fashion show allows designer to create infinite ideas by articulating the designer`s concept through not only garments but also other factors. In this research, We will analyze cases which are mixtures of digital technology and fashion show and will suggest a new paradigm of fashion show by producing an imaginary fashion show which cannot be easily articulated in an ordinary real fashion show, articulated by garments created by digital technology and graphic effects. The program used for this study is `DC Suite 2.0` developed by Physan and Digital Clothing Center of Seoul National University, available for 2D pattern production and 3D simulation. In addition, in order to enhance representation of the visual effects, Maya`s Qualoth and V-ray program which could be compatible with `DC Suite` were used to make 3D digital fashion show.

The explosive or volcanic scenes in motion pictures involve complex turbulent flow as its temperature and density vary in space. To simulate this turbulent flow of an inhomogeneous fluid, we propose a simple and efficient framework. Instead of explicitly computing the complex motion of this fluid dynamical instability, we first approximate the average motion of the fluid. Then, the high-resolution dynamics is computed using our new extended version of the vortex particle method with baroclinity. This baroclinity term makes turbulent effects by generating new vortex particles according to temperature/density distributions. Using our method, we efficiently simulated a complex scene with varying density and temperature.

This paper proposes a real-time simulation technique for thin shells undergoing large deformation. Shells are thin objects such as leaves and papers that can be abstracted as 2D structures. Development of a satisfactory physical model that runs in real-time but produces visually convincing animation of thin shells has been remaining a challenge in computer graphics. Rather than resorting to shell theory which involves the most complex formulations in continuum mechanics, we adopt the energy functions from the discrete shells proposed by Grinspun et al. [GHDS03]. For real-time integration of the governing equation, we develop a modal warping technique for shells. This new simulation framework results from making extensions to the original modal warping technique [CK05] which was developed for the simulation of 3D solids. We report experimental results, which show that the proposed method runs in real-time even for large meshes, and that it can simulate large bending and/or twisting deformations with acceptable realism.

This paper proposes a new technique for generating three-dimensional speech animation. The proposed technique takes advantage of both data-driven and machine learning approaches. It seeks to utilize the most relevant part of the captured utterances for the synthesis of input phoneme sequences. If highly relevant data are missing or lacking, then it utilizes less relevant (but more abundant) data and relies more heavily on machine learning for the lip-synch generation. This hybrid approach produces results that are more faithful to real data than conventional machine learning approaches, while being better able to handle incompleteness or redundancy in the database than conventional data-driven approaches. Experimental results, obtained by applying the proposed technique to the utterance of various words and phrases, show that (1) the proposed technique generates lip-synchs of different qualities depending on the availability of the data, and (2) the new technique produces more realistic results than conventional machine learning approaches.

Clothing simulation and animation are of great importance in computer animation. If cloth simulations could be improved to the point that they could generate realistic cloth motion in real-time, they would find uses in many aspects of daily life such as in fashion design and manufacturing. The area of cloth simulation and animation is full of technical challenges: creating more realistic results, achieving faster run-times, and developing methods capable of constructing and simulating more complex garments. This paper provides an overview of the key procedures involved in the creation of clothed characters, describes the current state-of-the-art techniques, and proposes the research problems that most require further study. Three technical aspects of cloth simulation are considered in this paper: garment construction, physically based simulation, and collision resolution.

This article presents a physically-based technique for simulating water. This work is motivated by the "stable fluids" method, developed by Stam [1999], to handle gaseous fluids. We extend this technique to water, which calls for the development of methods for modeling multiphase fluids and suppressing dissipation. We construct a multiphase fluid formulation by combining the Navier--Stokes equations with the level set method. By adopting constrained interpolation profile (CIP)-based advection, we reduce the numerical dissipation and diffusion significantly. We further reduce the dissipation by converting potentially dissipative cells into droplets or bubbles that undergo Lagrangian motion. Due to the multiphase formulation, the proposed method properly simulates the interaction of water with surrounding air, instead of simulating water in a void space. Moreover, the introduction of the nondissipative technique means that, in contrast to previous methods, the simulated water does not unnecessarily lose mass, and its motion is not damped to an unphysical extent. Experiments showed that the proposed method is stable and runs fast. It is demonstrated that two-dimensional simulation runs in real-time.

This article presents a novel constraint-based motion editing technique. On the basis of animator-specified kinematic and dynamic constraints, the method converts a given captured or animated motion to a physically plausible motion. In contrast to previous methods using spacetime optimization, we cast the motion editing problem as a constrained state estimation problem, based on the per-frame Kalman filter framework. The method works as a filter that sequentially scans the input motion to produce a stream of output motion frames at a stable interactive rate. Animators can tune several filter parameters to adjust to different motions, turn the constraints on or off based on their contributions to the final result, or provide a rough sketch (kinematic hint) as an effective way of producing the desired motion. Experiments on various systems show that the technique processes the motions of a human with 54 degrees of freedom, at about 150 fps when only kinematic constraints are applied, and at about 10 fps when both kinematic and dynamic constraints are applied. Experiments on various types of motion show that the proposed method produces remarkably realistic animations.

This paper proposes a real-time simulation technique for large deformations. Green's nonlinear strain tensor accurately models large deformations; however, time stepping of the resulting nonlinear system can be computationally expensive. Modal analysis based on a linear strain tensor has been shown to be suitable for real-time simulation, but is accurate only for moderately small deformations. In the present work, we identify the rotational component of an infinitesimal deformation and extend traditional linear modal analysis to track that component. We then develop a procedure to integrate the small rotations occurring at the nodal points. An interesting feature of our formulation is that it can implement both position and orientation constraints in a straightforward manner. These constraints can be used to interactively manipulate the shape of a deformable solid by dragging/twisting a set of nodes. Experiments show that the proposed technique runs in real-time, even for a complex model, and that it can simulate large bending and/or twisting deformations with acceptable realism.

In this paper, we develop a hairstyle modeling and animation technique specifically designed for human hairs, and we report several experimental results. Using simplified cantilever beam model and one-dimensional projective differential equations of angular momenta, we give a practical solution to the problem of enormous complexity. Even though our hair animation algorithm is an approximate solution, it includes all the relevant dynamic elements such as gravity, wind, inertia, air-resistance, hair-to-head, and hair-to-hair friction forces. Collision is an important element that makes a collection of hair strands look like hair. We develop an accurate but efficient hair-to-head and hair-to-hair collision detection and treatment algorithm. The algorithm produces quite realistic results; still it runs at an interactive speed. An interesting contribution of our algorithm is that it unifies hairstyle modeling and animation into a single equation, so that (1) hairstyling can be done under the effects of gravity and other internal or external forces, and (2) original hairstyle is more or less restored even after the initial hair is tangled by the application of external forces or head movements.

We describe a system to synthesize facial expressions by editing captured performances. For this purpose, we use the actuation of expression muscles to control facial expressions. We note that there have been numerous algorithms already developed for editing gross body motion. While the joint angle has direct effect on the configuration of the gross body, the muscle actuation has to go through a complicated mechanism to produce facial expressions. Therefore, we devote a significant part of this paper to establish the relationship between muscle actuation and facial surface deformation. We model the skin surface using finite element method to simulate the deformation caused by expression muscles. Then, we implement the inverse relationship, muscle actuation parameter estimation, to find the muscle actuation values from the trajectories of the markers on the performer’s face. Once the forward and inverse relationships are established, retargeting or editing a performance becomes an easy job. We apply the original performance data to different facial models with equivalent muscle structures, to produce similar expressions. We also produce novel expressions by deforming the original data curves of muscle actuation to satisfy the key-frame constraints imposed by animators.

This paper presents a method to retarget the motion of a character to another in real time. The technique is based on inverse rate control, which computes the changes in joint angles corresponding to the changes in end-effector position. While tracking the multiple end-effector trajectories of the original subject or character, our online motion retargetting also minimizes the joint angle differences by exploiting the kinematic redundancies of the animated model. This method can apply a captured motion to another anthropometry so that it can perform slightly different motion, while preserving the original motion characteristics. Because the above is done online, a real-time performance can be mapped to other characters. Moreover, if the method is used interactively during motion capture session, the feedback of retargetted motion on the screen provides more chances to get satisfactory results. As a by-product, our algorithm can be used to reduce measurement errors in restoring captured motion. The data enhancement improves the accuracy in both joint angles and end-effector positions. Experimental results show that our retargetting algorithm preserves high-frequency details of the original motion quite accurately. Copyright © 2000 John Wiley & Sons, Ltd.

In the edge contraction algorithm for surface simplification, two major steps are (i) ordering of the edges to be collapsed, and (ii) positioning of the new vertex to replace the collapsed edge. The accuracy of the simplified result greatly depends on which procedures are taken in the above steps. During the simplification process, degenerate cases can occur in which the optimization problem for the new vertex position produces multiple solutions. In the previous algorithms, such redundancy was utilized to achieve other desirable effects (e.g, increasing the regularness of the triangles). In this paper we give a complete characterization of the geometric situation for the degenerate cases, and show that performing edge contraction procedure in those cases can produce unexpected damage to the original shape. To cope with the problem, we propose a new procedure, called edge elimination, which eliminates the degenerate edge and all the adjacent ones, and then retriangulates the hole in a way the geometrical ...