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Now showing 1 - 10 of 13
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    Implicit Formulation for SPH-based Viscous Fluids
    (The Eurographics Association and John Wiley & Sons Ltd., 2015) Takahashi, Tetsuya; Dobashi, Yoshinori; Fujishiro, Issei; Nishita, Tomoyuki; Lin, Ming C.; Olga Sorkine-Hornung and Michael Wimmer
    We propose a stable and efficient particle-based method for simulating highly viscous fluids that can generate coiling and buckling phenomena and handle variable viscosity. In contrast to previous methods that use explicit integration, our method uses an implicit formulation to improve the robustness of viscosity integration, therefore enabling use of larger time steps and higher viscosities. We use Smoothed Particle Hydrodynamics to solve the full form of viscosity, constructing a sparse linear system with a symmetric positive definite matrix, while exploiting the variational principle that automatically enforces the boundary condition on free surfaces. We also propose a new method for extracting coefficients of the matrix contributed by second-ring neighbor particles to efficiently solve the linear system using a conjugate gradient solver. Several examples demonstrate the robustness and efficiency of our implicit formulation over previous methods and illustrate the versatility of our method.
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    Eye-tracktive: Measuring Attention to Body Parts when Judging Human Motions
    (The Eurographics Association, 2015) Ennis, Cathy; Hoyet, Ludovic; O'Sullivan, Carol; B. Bickel and T. Ritschel
    Virtual humans are often endowed with human-like characteristics to make them more appealing and engaging. Motion capture is a reliable way to represent natural motion on such characters, thereby allowing a wide range of animations to be automatically created and replicated. However, interpersonal differences in actors' performances can be subtle and complex, yet have a strong effect on the human observer. Such effects can be very difficult to express quantitatively or indeed even qualitatively. We investigate two subjective human motion characteristics: attractiveness and distinctiveness. We conduct a perceptual experiment, where participants' eye movements are tracked while they rate the motions of a range of actors. We found that participants fixate mostly on the torso, regardless of gait and actor sex, and very little on the limbs. However, they self-reported that they used hands, elbows and feet in their judgments, indicating a holistic approach to the problem.
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    Improving Sampling-based Motion Control
    (The Eurographics Association and John Wiley & Sons Ltd., 2015) Liu, Libin; Yin, KangKang; Guo, Baining; Olga Sorkine-Hornung and Michael Wimmer
    We address several limitations of the sampling-based motion control method of Liu et at. [LYvdP 10]. The key insight is to learn from the past control reconstruction trials through sample distribution adaptation. Coupled with a sliding window scheme for better performance and an averaging method for noise reduction, the improved algorithm can efficiently construct open-loop controls for long and challenging reference motions in good quality. Our ideas are intuitive and the implementations are simple. We compare the improved algorithm with the original algorithm both qualitatively and quantitatively, and demonstrate the effectiveness of the improved algorithm with a variety of motions ranging from stylized walking and dancing to gymnastic and Martial Arts routines.
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    State of the Art in Hand and Finger Modeling and Animation
    (The Eurographics Association and John Wiley & Sons Ltd., 2015) Wheatland, Nkenge; Wang, Yingying; Song, Huaguang; Neff, Michael; Zordan, Victor; Jörg, Sophie; K. Hormann and O. Staadt
    The human hand is a complex biological system able to perform numerous tasks with impressive accuracy and dexterity. Gestures furthermore play an important role in our daily interactions, and humans are particularly skilled at perceiving and interpreting detailed signals in communications. Creating believable hand motions for virtual characters is an important and challenging task. Many new methods have been proposed in the Computer Graphics community within the last years, and significant progress has been made towards creating convincing, detailed hand and finger motions. This state of the art report presents a review of the research in the area of hand and finger modeling and animation. Starting with the biological structure of the hand and its implications for how the hand moves, we discuss current methods in motion capturing hands, data-driven and physics-based algorithms to synthesize their motions, and techniques to make the appearance of the hand model surface more realistic. We then focus on areas in which detailed hand motions are crucial, such as manipulation and communication. Our report concludes by describing emerging trends and applications for virtual hand animation.
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    Adaptable Anatomical Models for Realistic Bone Motion Reconstruction
    (The Eurographics Association and John Wiley & Sons Ltd., 2015) Zhu, Lifeng; Hu, Xiaoyan; Kavan, Ladislav; Olga Sorkine-Hornung and Michael Wimmer
    We present a system to reconstruct subject-specific anatomy models while relying only on exterior measurements represented by point clouds. Our model combines geometry, kinematics, and skin deformations (skinning). This joint model can be adapted to different individuals without breaking its functionality, i.e., the bones and the skin remain well-articulated after the adaptation.We propose an optimization algorithm which learns the subject-specific (anthropometric) parameters from input point clouds captured using commodity depth cameras. The resulting personalized models can be used to reconstruct motion of human subjects. We validate our approach for upper and lower limbs, using both synthetic data and recordings of three different human subjects. Our reconstructed bone motion is comparable to results obtained by optical motion capture (Vicon) combined with anatomically-based inverse kinematics (OpenSIM). We demonstrate that our adapted models better preserve the joint structure than previous methods such as OpenSIM or Anatomy Transfer.
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    Real-Time Subspace Integration for Example-Based Elastic Material
    (The Eurographics Association and John Wiley & Sons Ltd., 2015) Zhang, Wenjing; Zheng, Jianmin; Thalmann, Nadia Magnenat; Olga Sorkine-Hornung and Michael Wimmer
    Example-based material allows simulating complex material behaviors in an art-directed way. This paper presents a method for fast subspace integration for example-based elastic material, which is suitable for real-time simulation in computer graphics. At the core of the method is the formulation of a new potential using example-based Green strain tensors. By using this potential, the deformation can be attracted towards the example-based deformation feature space, the example weights can be explicitly obtained and the internal force can be decomposed into the conventional one and an additional one induced by the examples. The real-time subspace integration is then developed with subspace integration costs independent of geometric complexity, and both the reduced conventional internal force and additional one being cubic polynomials in reduced coordinates. Experiments demonstrate that our method can achieve real-time simulation while providing comparable quality with the prior art.
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    A Dimension-reduced Pressure Solver for Liquid Simulations
    (The Eurographics Association and John Wiley & Sons Ltd., 2015) Ando, Ryoichi; Thürey, Nils; Wojtan, Chris; Olga Sorkine-Hornung and Michael Wimmer
    This work presents a method for efficiently simplifying the pressure projection step in a liquid simulation. We first devise a straightforward dimension reduction technique that dramatically reduces the cost of solving the pressure projection. Next, we introduce a novel change of basis that satisfies free-surface boundary conditions exactly, regardless of the accuracy of the pressure solve. When combined, these ideas greatly reduce the computational complexity of the pressure solve without compromising free surface boundary conditions at the highest level of detail. Our techniques are easy to parallelize, and they effectively eliminate the computational bottleneck for large liquid simulations.
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    Composition-Aware Scene Optimization for Product Images
    (The Eurographics Association and John Wiley & Sons Ltd., 2015) Liu, Tianqiang; McCann, Jim; Li, Wilmot; Funkhouser, Thomas; Olga Sorkine-Hornung and Michael Wimmer
    Increasingly, companies are creating product advertisements and catalog images using computer renderings of 3D scenes. A common goal for these companies is to create aesthetically appealing compositions that highlight objects of interest within the context of a scene. Unfortunately, this goal is challenging, not only due to the need to balance the trade-off among aesthetic principles and design constraints, but also because of the huge search space induced by possible camera parameters, object placement, material choices, etc. Previous methods have investigated only optimization of camera parameters. In this paper, we develop a tool that starts from an initial scene description and a set of high-level constraints provided by a stylist and then automatically generates an optimized scene whose 2D composition is improved. It does so by locally adjusting the 3D object transformations, surface materials, and camera parameters. The value of this tool is demonstrated in a variety of applications motivated by product catalogs, including rough layout refinement, detail image creation, home planning, cultural customization, and text inlay placement. Results of a perceptual study indicate that our system produces images preferable for product advertisement compared to a more traditional camera-only optimization.
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    Sketch-Based Controllers for Blendshape Facial Animation
    (The Eurographics Association, 2015) Cetinaslan, Ozan; Orvalho, Verónica; Lewis, John; B. Bickel and T. Ritschel
    The blendshape approach is a widely used technique to generate realistic facial animation. However, creating blendshape facial animations using traditional weight editing tools requires either memorizing the function of a large number of parameters, or a trial-and-error search in a high-dimensional space. Direct manipulation interfaces address this problem, allowing the artist to directly move and pin manipulators placed on the surface of the face. Placing manipulators is an open-ended and slightly unnatural task for artists however. In this paper we present a sketch-based approach to this problem, inspired by artists' brush painting on canvas. In this approach the artist simply sketches directly onto the 3D model the positions of the manipulators that they feel are needed to produce particular facial expression. The manipulators activate the blendshapes in the model and allow the user to interactively create the desired facial poses by a dragging operation in screen coordinates. Our hybrid method can be used with any blendshape facial model and allows producing expeditious manipulation in an intuitive way.
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    Egocentric Normalization of Kinematic Path
    (The Eurographics Association, 2015) Molla, Eray; Boulic, Ronan; B. Solenthaler and E. Puppo
    We focus on retargetting the class of movements involving self-interactions onto characters with different size and proportion. Such postures may produce self-collisions and/or alter the intended semantics. We introduce a technique to normalize the spatial relationship vectors between the body parts of the source character. This allows for morphological adaptation of these vectors onto the target characters, hence preserving the semantics in postures with and without body-contact.