bluuebunny/crossref_metadata_2025 huggingface dataset:
Momentum-dependent local ansatz approach to correlated electrons
Authors: Kakehashi Yoshiro , Chandra Sumal , Rowlands Derwyn , Patoary M. Atiqur R.
Published: July 2014

The wavefunction method provides us with a useful tool to describe electron correlations in solids at the ground state. In this paper we review the recent development of the momentum-dependent local ansatz (MLA) wavefunction. It is constructed by taking into account two-particle excited states projected onto the local orbitals, and the momentum-dependent amplitudes of these states are chosen as variational parameters. The MLA describes accurately correlated electron states from the weak to the intermediate Coulomb interaction regime in infinite dimensions, and works well even in the strongly correlated region by introducing a new starting wavefunction called the hybrid (HB) wavefunction. The MLA-HB is therefore shown to overcome the limitation of the original local ansatz (LA) wavefunction as well as the Gutzwiller wavefunction. In particular, the calculated quasiparticle weight versus Coulomb interaction curve is shown to be close to that obtained by the numerical renormalization group approach. It is also shown that the MLA is applicable to the first-principles Hamiltonian.
Adsorption of rare-earth atoms onl silicon carbide nanotube: a density-functional study
Authors: An Zhiwei , Shen Jiang
Published: July 2014

In this paper, we investigate the adsorption of a series of rare-earth (RE) metal atoms ( La , Pr , Nd , Sm and Eu ) on the pristine zigzag (8, 0) silicon carbide nanotube ( SiCNT ) using density functional theory (DFT). Main focuses are placed on the stable adsorption sites, the corresponding binding energies, and the modified electronic properties of the SiC nanotubes due to the adsorbates. A single RE atom prefers to adsorb strongly at the hollow site with relatively high binding energy (larger than 1.0 eV). Due to the rolling effect of single-walled SiCNTs , the inside configurations are more stable than the outside ones. For RE-adsorbed systems, the adsorption of metal atoms induces certain impurity states within the band gap of the pristine SiCNT . Furthermore, we analyze there exists hybridizations between RE-5d, 6s, C -2p and Si -3p orbitals for the RE atom adsorption on the SiCNTs .
Cation distribution, structural and electric studies on cadmium substituted nickel–zinc ferrite
Authors: Prasad B. B. V. S. Vara
Published: July 2014

The structural and electric properties of Ni 0.65-x Zn 0.35 Cd x Fe 2 O 4 (0 ≤ x ≤ 0.2) prepared by standard ceramic technique, have been studied. For all x values, X-ray powder diffraction was performed and the lattice constants and oxygen parameters were drawn from experimental data. Based on these values, other structural parameters like cation–cation, cation–anion distances, bond angles and hopping length were calculated, and the cation distribution was proposed by comparing observed and calculated X-ray diffraction intensities. It was found that substitution of larger cadmium into the lattice resulted in a significant change in the structural parameters. The microstructure of the samples was investigated using SEM micrographs and we found a substantial grain growth (observed mainly for x = 0.16 and 0.20) due to cadmium diffusion. Carrier mobilities for all samples were drawn from our DC electrical conductivity results and the variation of mobility with composition and temperature is presented. Dielectric measurements were performed at a standard frequency 1 kHz and the dielectric constant and loss factor were found to decrease first from x = 0 to x = 0.12 with the abrupt increase above this composition.
Anisotropy angle of the DST-emissions
Authors: Cardone F. , Duro S.
Published: July 2014

In our previous experiments, it has been found that an angle of asymmetry is present when the breakdown of the Lorenz invariance occurs. We want to make sure that this angle is present as a preferred direction of emission for α-rays and neutrons emitted as a result of piezonuclear reactions, or better, the reactions in deformed spacetime (DST-reactions: deformed spacetime reactions, for more details on the DST-reactions [see G. Albertini et al., Material and Process for Energy, ed. A. Mendez-Vilas (Formatex, 2013)]. For this purpose, we analyze the experiment of Ancona for α-ray emission and the experiment of Cagliari for neutrons emission. In this work, we present an example for each group of experiments. These experimental examples are significant because they show the behavior of the emissions detected in all the measures.
MOLECULAR DYNAMICS STUDY OF PTX ADSORPTION ONTO N-DOPED GRAPHENE IN VACUUM AND AQUEOUS ENVIRONMENTS
Authors: AZIZI ALI , EBRAHIMI SADOLLAH
Published: July 2014

In this study, the adsorption of Paclitaxel (PTX) drug molecule onto graphene doped with nitrogen atoms ( N -doped graphene) in vacuum and aqueous environments has been investigated. To do this, we have employed a series of very accurate molecular dynamics (MD) simulations to reveal the effect of N atoms concentration on drug molecule adsorption. The critical value of N adatoms is obtained. The water concentration, adsorption energy, and average distance of drug molecule from surface are calculated. Overall, our findings provide crucial information for the performance of N -doped graphene in drug delivery.
On the simultaneous edge coloring of graphs
Authors: Bagheri Gh. Behrooz , Omoomi Behnaz
Published: July 2014

A μ-simultaneous edge coloring of graph G is a set of μ proper edge colorings of G with a same color set such that for each vertex, the sets of colors appearing on the edges incident to that vertex are the same in each coloring and no edge receives the same color in any two colorings. The μ-simultaneous edge coloring of bipartite graphs has a close relation with μ-way Latin trades. Mahdian et al. (2000) conjectured that every bridgeless bipartite graph is 2-simultaneous edge colorable. Luo et al. (2004) showed that every bipartite graphic sequence S with all its elements greater than one, has a realization that admits a 2-simultaneous edge coloring. In this paper, the μ-simultaneous edge coloring of graphs is studied. Moreover, the properties of the extremal counterexample to the above conjecture are investigated. Also, a relation between 2-simultaneous edge coloring of a graph and a cycle double cover with certain properties is shown and using this relation, some results about 2-simultaneous edge colorable graphs are obtained.
Pseudopodial silica absorption hypothesis (PSA hypothesis): a new function of pseudopodia in living radiolarian polycystine cells
Authors: Ogane Kaoru , Suzuki Noritoshi , Tuji Akihiro , Hori Rie S.
Published: July 2014

Abstract. The secretion process of the siliceous skeleton in polycystine radiolarians has drawn a great deal of interest during the last century; however, little is known about the actual physiological process of silica deposition. Recently, the PDMPO (2-(4-pyridyl)-5-[(4-(2-dimethylaminoethylaminocarbamoyl) methoxy)-phenyl] oxazole) method for staining silica deposition sites in polycystines was developed. In the present study we examined over 30 polycystine cells with PDMPO and found that both the skeletons and pseudopodia of three species (Lithelius sp., Rhizosphaera trigonacantha and Arachnosphaera hexasphaera) were stained and emitted green fluorescent light. Staining of the skeleton was probably the result of skeletal thickening growth, whereas staining of the pseudopodia may indicate that siliceous matter is assimilated within pseudopodia. We refer to this hypothesis as the ‘pseudopodial silica absorption hypothesis’ (PSA hypothesis). If this hypothesis is correct, PSA is an intermittent process, and the absorbed silica within pseudopodia is quickly transferred to the cytokalymma where it is deposited on the skeleton. To date, the PSA process has been observed in only the three species cited above; therefore we are unable to evaluate whether the PSA process is unique to these species or a common process that occurs in all polycystines; further investigation is necessary.
High-order similarity relations in radiative transfer
Authors: Zhao Shuang , Ramamoorthi Ravi , Bala Kavita
Published: July 2014

Radiative transfer equations (RTEs) with different scattering parameters can lead to identical solution radiance fields. Similarity theory studies this effect by introducing a hierarchy of equivalence relations called "similarity relations". Unfortunately, given a set of scattering parameters, it remains unclear how to find altered ones satisfying these relations, significantly limiting the theory's practical value. This paper presents a complete exposition of similarity theory, which provides fundamental insights into the structure of the RTE's parameter space. To utilize the theory in its general high-order form, we introduce a new approach to solve for the altered parameters including the absorption and scattering coefficients as well as a fully tabulated phase function. We demonstrate the practical utility of our work using two applications: forward and inverse rendering of translucent media. Forward rendering is our main application, and we develop an algorithm exploiting similarity relations to offer "free" speedups for Monte Carlo rendering of optically dense and forward-scattering materials. For inverse rendering, we propose a proof-of-concept approach which warps the parameter space and greatly improves the efficiency of gradient descent algorithms. We believe similarity theory is important for simulating and acquiring volume-based appearance, and our approach has the potential to benefit a wide range of future applications in this area.
Wire mesh design
Authors: Garg Akash , Sageman-Furnas Andrew O. , Deng Bailin , Yue Yonghao , Grinspun Eitan , Pauly Mark , Wardetzky Max
Published: July 2014

We present a computational approach for designing
wire meshes
, i.e., freeform surfaces composed of woven wires arranged in a regular grid. To facilitate shape exploration, we map material properties of wire meshes to the geometric model of
Chebyshev nets
. This abstraction is exploited to build an efficient optimization scheme. While the theory of Chebyshev nets suggests a highly constrained design space, we show that allowing controlled deviations from the underlying surface provides a rich shape space for design exploration. Our algorithm balances globally coupled material constraints with aesthetic and geometric design objectives that can be specified by the user in an interactive design session. In addition to sculptural art, wire meshes represent an innovative medium for industrial applications including composite materials and architectural façades. We demonstrate the effectiveness of our approach using a variety of digital and physical prototypes with a level of shape complexity unobtainable using previous methods.
Exploratory font selection using crowdsourced attributes
Authors: O'Donovan Peter , Lībeks Jānis , Agarwala Aseem , Hertzmann Aaron
Published: July 2014

This paper presents interfaces for exploring large collections of fonts for design tasks. Existing interfaces typically list fonts in a long, alphabetically-sorted menu that can be challenging and frustrating to explore. We instead propose three interfaces for font selection. First, we organize fonts using high-level descriptive attributes, such as "dramatic" or "legible." Second, we organize fonts in a tree-based hierarchical menu based on perceptual similarity. Third, we display fonts that are most similar to a user's currently-selected font. These tools are complementary; a user may search for "graceful" fonts, select a reasonable one, and then refine the results from a list of fonts similar to the selection. To enable these tools, we use crowdsourcing to gather font attribute data, and then train models to predict attribute values for new fonts. We use attributes to help learn a font similarity metric using crowdsourced comparisons. We evaluate the interfaces against a conventional list interface and find that our interfaces are preferred to the baseline. Our interfaces also produce better results in two real-world tasks: finding the nearest match to a target font, and font selection for graphic designs.
Tangible and modular input device for character articulation
Authors: Jacobson Alec , Panozzo Daniele , Glauser Oliver , Pradalier Cédric , Hilliges Otmar , Sorkine-Hornung Olga
Published: July 2014

Articulation of 3D characters requires control over many degrees of freedom: a difficult task with standard 2D interfaces. We present a tangible input device composed of interchangeable, hot-pluggable parts. Embedded sensors measure the device's pose at rates suitable for real-time editing and animation. Splitter parts allow branching to accommodate any skeletal tree. During assembly, the device recognizes topological changes as individual parts or pre-assembled subtrees are plugged and unplugged. A novel semi-automatic registration approach helps the user quickly map the device's degrees of freedom to a virtual skeleton inside the character. User studies report favorable comparisons to mouse and keyboard interfaces for the tasks of target acquisition and pose replication. Our device provides input for character rigging and automatic weight computation, direct skeletal deformation, interaction with physical simulations, and handle-based variational geometric modeling.
Defending continuous collision detection against errors
Authors: Wang Huamin
Published: July 2014

Numerical errors and rounding errors in continuous collision detection (CCD) can easily cause collision detection failures if they are not handled properly. A simple and effective approach is to use error tolerances, as shown in many existing CCD systems. Unfortunately, finding the optimal tolerance values is a difficult problem for users. Larger tolerance values will introduce false positive artifacts, while smaller tolerance values may cause collisions to be undetected. The biggest issue here is that we do not know whether or when CCD will fail, even though failures are extremely rare. In this paper, we demonstrate a set of simple modifications to make a basic CCD implementation failure-proof. Using error analysis, we prove the safety of this method and we formulate suggested tolerance values to reduce false positives. The resulting algorithms are safe, automatic, efficient, and easy to implement.
Physics-inspired adaptive fracture refinement
Authors: Chen Zhili , Yao Miaojun , Feng Renguo , Wang Huamin
Published: July 2014

Physically based animation of detailed fracture effects is not only computationally expensive, but also difficult to implement due to numerical instability. In this paper, we propose a physics-inspired approach to enrich low-resolution fracture animation by realistic fracture details. Given a custom-designed material strength field, we adaptively refine a coarse fracture surface into a detailed one, based on a discrete gradient descent flow. Using the new fracture surface, we then generate a high-resolution fracture animation with details on both the fracture surface and the exterior surface. Our experiment shows that this approach is simple, fast, and friendly to user design and control. It can generate realistic fracture animations within a few seconds.
Eyeglasses-free display
Authors: Huang Fu-Chung , Wetzstein Gordon , Barsky Brian A. , Raskar Ramesh
Published: July 2014

Millions of people worldwide need glasses or contact lenses to see or read properly. We introduce a computational display technology that predistorts the presented content for an observer, so that the target image is perceived without the need for eyewear. By designing optics in concert with prefiltering algorithms, the proposed display architecture achieves significantly higher resolution and contrast than prior approaches to vision-correcting image display. We demonstrate that inexpensive light field displays driven by efficient implementations of 4D prefiltering algorithms can produce the desired vision-corrected imagery, even for higher-order aberrations that are difficult to be corrected with glasses. The proposed computational display architecture is evaluated in simulation and with a low-cost prototype device.
Flower modeling via X-ray computed tomography
Authors: Ijiri Takashi , Yoshizawa Shin , Yokota Hideo , Igarashi Takeo
Published: July 2014

This paper presents a novel three dimensional (3D) flower modeling technique that utilizes an X-ray computed tomography (CT) system and real-world flowers. Although a CT system provides volume data that captures the internal structures of flowers, it is difficult to accurately segment them into regions of particular organs and model them as smooth surfaces because a flower consists of thin organs that contact one another. We thus introduce a semi-automatic modeling technique that is based on a new active contour model with energy functionals designed for flower CT. Our key idea is to approximate flower components by two important primitives, a shaft and a sheet. Based on our active contour model, we also provide novel user interfaces and a numerical scheme to fit these primitives so as to reconstruct realistic thin flower organs efficiently. To demonstrate the feasibility of our technique, we provide various flower models reconstructed from CT volumes.
Point morphology
Authors: Calderon Stéphane , Boubekeur Tamy
Published: July 2014

We introduce a complete morphological analysis framework for 3D point clouds. Starting from an unorganized point set sampling a surface, we propose morphological operators in the form of projections, allowing to sample erosions, dilations, closings and openings of an object without any explicit mesh structure. Our framework supports structuring elements with arbitrary shape, accounts robustly for geometric and morphological sharp features, remains efficient at large scales and comes together with a specific adaptive sampler. Based on this meshless framework, we propose applications which benefit from the non-linear nature of morphological analysis and can be expressed as simple sequences of our operators, including medial axis sampling, hysteresis shape filtering and geometry-preserving topological simplification.
Intrinsic video and applications
Authors: Ye Genzhi , Garces Elena , Liu Yebin , Dai Qionghai , Gutierrez Diego
Published: July 2014

We present a method to decompose a
video
into its intrinsic components of reflectance and shading, plus a number of related example applications in video editing such as segmentation, stylization, material editing, recolorization and color transfer. Intrinsic decomposition is an ill-posed problem, which becomes even more challenging in the case of video due to the need for temporal coherence and the potentially large memory requirements of a global approach. Additionally, user interaction should be kept to a minimum in order to ensure efficiency. We propose a probabilistic approach, formulating a Bayesian Maximum a Posteriori problem to drive the propagation of clustered reflectance values from the first frame, and defining additional constraints as priors on the reflectance and shading. We explicitly leverage temporal information in the video by building a causal-anticausal, coarse-to-fine iterative scheme, and by relying on optical flow information. We impose no restrictions on the input video, and show examples representing a varied range of difficult cases. Our method is the first one designed explicitly for video; moreover, it naturally ensures temporal consistency, and compares favorably against the state of the art in this regard.
Sensitivity-optimized rigging for example-based real-time clothing synthesis
Authors: Xu Weiwei , Umentani Nobuyuki , Chao Qianwen , Mao Jie , Jin Xiaogang , Tong Xin
Published: July 2014

We present a real-time solution for generating detailed clothing deformations from pre-computed clothing shape examples. Given an input pose, it synthesizes a clothing deformation by blending skinned clothing deformations of nearby examples controlled by the body skeleton. Observing that cloth deformation can be well modeled with sensitivity analysis driven by the underlying skeleton, we introduce a sensitivity based method to construct a pose-dependent rigging solution from sparse examples. We also develop a sensitivity based blending scheme to find nearby examples for the input pose and evaluate their contributions to the result. Finally, we propose a stochastic optimization based greedy scheme for sampling the pose space and generating example clothing shapes. Our solution is fast, compact and can generate realistic clothing animation results for various kinds of clothes in real time.
Style transfer for headshot portraits
Authors: Shih YiChang , Paris Sylvain , Barnes Connelly , Freeman William T. , Durand Frédo
Published: July 2014

Headshot portraits are a popular subject in photography but to achieve a compelling visual style requires advanced skills that a casual photographer will not have. Further, algorithms that automate or assist the stylization of generic photographs do not perform well on headshots due to the feature-specific, local retouching that a professional photographer typically applies to generate such portraits. We introduce a technique to transfer the style of an example headshot photo onto a new one. This can allow one to easily reproduce the look of renowned artists. At the core of our approach is a new multiscale technique to robustly transfer the local statistics of an example portrait onto a new one. This technique matches properties such as the local contrast and the overall lighting direction while being tolerant to the unavoidable differences between the faces of two different people. Additionally, because artists sometimes produce entire headshot collections in a common style, we show how to automatically find a good example to use as a reference for a given portrait, enabling style transfer without the user having to search for a suitable example for each input. We demonstrate our approach on data taken in a controlled environment as well as on a large set of photos downloaded from the Internet. We show that we can successfully handle styles by a variety of different artists.
Pinlight displays
Authors: Maimone Andrew , Lanman Douglas , Rathinavel Kishore , Keller Kurtis , Luebke David , Fuchs Henry
Published: July 2014

We present a novel design for an optical see-through augmented reality display that offers a wide field of view and supports a compact form factor approaching ordinary eyeglasses. Instead of conventional optics, our design uses only two simple hardware components: an LCD panel and an array of point light sources (implemented as an edge-lit, etched acrylic sheet) placed directly in front of the eye, out of focus. We code the point light sources through the LCD to form miniature see-through projectors. A virtual aperture encoded on the LCD allows the projectors to be tiled, creating an arbitrarily wide field of view. Software rearranges the target augmented image into tiled sub-images sent to the display, which appear as the correct image when observed out of the viewer's accommodation range. We evaluate the design space of tiled point light projectors with an emphasis on increasing spatial resolution through the use of eye tracking. We demonstrate feasibility through software simulations and a real-time prototype display that offers a 110° diagonal field of view in the form factor of large glasses and discuss remaining challenges to constructing a practical display.
Multimaterial mesh-based surface tracking
Authors: Da Fang , Batty Christopher , Grinspun Eitan
Published: July 2014

We present a triangle mesh-based technique for tracking the evolution of three-dimensionalmultimaterial interfacesundergoing complex deformations. It is the first non-manifold triangle mesh tracking method to simultaneously maintain intersection-free meshes and support the proposed broad set of multimaterial remeshing and topological operations. We represent the interface as a non-manifold triangle mesh with material labels assigned to each half-face to distinguish volumetric regions. Starting from proposed application-dependent vertex velocities, we deform the mesh, seeking a non-intersecting, watertight solution. This goal necessitates development of various collision-safe, label-aware non-manifold mesh operations: multimaterial mesh improvement; T1 and T2 processes, topological transitions arising in foam dynamics and multiphase flows; and multimaterial merging, in which a new interface is created between colliding materials. We demonstrate the robustness and effectiveness of our approach on a range of scenarios including geometric flows and multiphase fluid animation.
From capture to simulation
Authors: Gregson James , Ihrke Ivo , Thuerey Nils , Heidrich Wolfgang
Published: July 2014

We explore the connection between fluid capture, simulation and proximal methods, a class of algorithms commonly used for inverse problems in image processing and computer vision. Our key finding is that the proximal operator constraining fluid velocities to be divergence-free is directly equivalent to the pressure-projection methods commonly used in incompressible flow solvers. This observation lets us treat the inverse problem of fluid tracking as a constrained flow problem all while working in an efficient, modular framework. In addition it lets us tightly couple fluid simulation into flow tracking, providing a global prior that significantly increases tracking accuracy and temporal coherence as compared to previous techniques. We demonstrate how we can use these improved results for a variety of applications, such as re-simulation, detail enhancement, and domain modification. We furthermore give an outlook of the applications beyond fluid tracking that our proximal operator framework could enable by exploring the connection of deblurring and fluid guiding.
Robust field-aligned global parametrization
Authors: Myles Ashish , Pietroni Nico , Zorin Denis
Published: July 2014

We present a robust method for computing locally bijective global parametrizations aligned with a given cross-field. The singularities of the parametrization in general agree with singularities of the field, except in a small number of cases when several additional cones need to be added in a controlled way. Parametric lines can be constrained to follow an arbitrary set of feature lines on the surface. Our method is based on constructing an initial quad patch partition using robust cross-field integral line tracing. This process is followed by an algorithm modifying the quad layout structure to ensure that consistent parametric lengths can be assigned to the edges. For most meshes, the layout modification algorithm does not add new singularities; a small number of singularities may be added to resolve an explicitly described set of layouts. We demonstrate that our algorithm succeeds on a test data set of over a hundred meshes.
Spin-it
Authors: Bächer Moritz , Whiting Emily , Bickel Bernd , Sorkine-Hornung Olga
Published: July 2014

Spinning tops and yo-yos have long fascinated cultures around the world with their unexpected, graceful motions that seemingly elude gravity. We present an algorithm to generate designs for spinning objects by optimizing rotational dynamics properties. As input, the user provides a solid 3D model and a desired axis of rotation. Our approach then modifies the mass distribution such that the principal directions of the moment of inertia align with the target rotation frame. We augment the model by creating voids inside its volume, with interior fill represented by an adaptive multi-resolution voxelization. The discrete voxel fill values are optimized using a continuous, nonlinear formulation. Further, we optimize for rotational stability by maximizing the dominant principal moment. We extend our technique to incorporate deformation and multiple materials for cases where internal voids alone are insufficient. Our method is well-suited for a variety of 3D printed models, ranging from characters to abstract shapes. We demonstrate tops and yo-yos that spin surprisingly stably despite their asymmetric appearance.
Robust and accurate skeletal rigging from mesh sequences
Authors: Le Binh Huy , Deng Zhigang
Published: July 2014

We introduce an example-based rigging approach to automatically generate linear blend skinning models with skeletal structure. Based on a set of example poses, our approach can output its skeleton, joint positions, linear blend skinning weights, and corresponding bone transformations. The output can be directly used to set up skeleton-based animation in various 3D modeling and animation software as well as game engines. Specifically, we formulate the solving of a linear blend skinning model with a skeleton as an optimization with joint constraints and weight smoothness regularization, and solve it using an iterative rigging algorithm that (i) alternatively updates skinning weights, joint locations, and bone transformations, and (ii) automatically prunes redundant bones that can be generated by an over-estimated bone initialization. Due to the automatic redundant bone pruning, our approach is more robust than existing example-based rigging approaches. Furthermore, in terms of rigging accuracy, even with a single set of parameters, our approach can soundly outperform state of the art methods on various types of experimental datasets including humans, quadrupled animals, and highly deformable models.
Designing inflatable structures
Authors: Skouras Mélina , Thomaszewski Bernhard , Kaufmann Peter , Garg Akash , Bickel Bernd , Grinspun Eitan , Gross Markus
Published: July 2014

We propose an interactive, optimization-in-the-loop tool for designing inflatable structures. Given a target shape, the user draws a network of seams defining desired segment boundaries in 3D. Our method computes optimally-shaped flat panels for the segments, such that the inflated structure is as close as possible to the target while satisfying the desired seam positions. Our approach is underpinned by physics-based pattern optimization, accurate coarse-scale simulation using tension field theory, and a specialized constraint-optimization method. Our system is fast enough to warrant interactive exploration of different seam layouts, including internal connections, and their effects on the inflated shape. We demonstrate the resulting design process on a varied set of simulation examples, some of which we have fabricated, demonstrating excellent agreement with the design intent.
Build-to-last
Authors: Lu Lin , Sharf Andrei , Zhao Haisen , Wei Yuan , Fan Qingnan , Chen Xuelin , Savoye Yann , Tu Changhe , Cohen-Or Daniel , Chen Baoquan
Published: July 2014

The emergence of low-cost 3D printers steers the investigation of new geometric problems that control the quality of the fabricated object. In this paper, we present a method to reduce the material cost and weight of a given object while providing a durable printed model that is resistant to impact and external forces.

We introduce a hollowing optimization algorithm based on the concept of
honeycomb-cells
structure. Honeycombs structures are known to be of minimal material cost while providing strength in tension. We utilize the Voronoi diagram to compute irregular honeycomb-like volume tessellations which define the inner structure. We formulate our problem as a
strength--to--weight
optimization and cast it as mutually finding an optimal interior tessellation and its maximal
hollowing
subject to relieve the interior stress. Thus, our system allows to
build-to-last
3D printed objects with large control over their strength-to-weight ratio and easily model various interior structures. We demonstrate our method on a collection of 3D objects from different categories. Furthermore, we evaluate our method by printing our hollowed models and measure their stress and weights.
Interactive manipulation of large-scale crowd animation
Authors: Kim Jongmin , Seol Yeongho , Kwon Taesoo , Lee Jehee
Published: July 2014

Editing large-scale crowd animation is a daunting task due to the lack of an efficient manipulation method. This paper presents a novel cage-based editing method for large-scale crowd animation. The cage encloses animated characters and supports convenient space/time manipulation methods that were unachievable with previous approaches. The proposed method is based on a combination of cage-based deformation and as-rigid-as-possible deformation with a set of constraints integrated into the system to produce desired results. Our system allows animators to edit existing crowd animations intuitively with real-time performance while maintaining complex interactions between individual characters. Our examples demonstrate how our cage-based user interfaces mitigate the time and effort for the user to manipulate large crowd animation.
Inverse-Foley animation
Authors: Langlois Timothy R. , James Doug L.
Published: July 2014

In this paper, we introduce
Inverse-Foley Animation
, a technique for optimizing rigid-body animations so that contact events are synchronized with input sound events. A precomputed database of randomly sampled rigid-body contact events is used to build a contact-event graph, which can be searched to determine a plausible sequence of contact events synchronized with the input sound's events. To more easily find motions with matching contact times, we allow transitions between simulated contact events using a motion blending formulation based on modified contact impulses. We fine tune synchronization by slightly retiming ballistic motions. Given a sound, our system can synthesize synchronized motions using graphs built with hundreds of thousands of precomputed motions, and millions of contact events. Our system is easy to use, and has been used to plan motions for hundreds of sounds, and dozens of rigid-body models.
Frame fields
Authors: Panozzo Daniele , Puppo Enrico , Tarini Marco , Sorkine-Hornung Olga
Published: July 2014

We introduce frame fields, which are a non-orthogonal and non-unit-length generalization of cross fields. Frame fields represent smoothly varying linear transformations on tangent spaces of a surface. We propose an algorithm to create discrete, dense frame fields that satisfy a sparse set of constraints. By computing a surface deformation that warps a frame field into a cross field, we generalize existing quadrangulation algorithms to generate anisotropic and non-uniform quad meshes whose elements shapes match the frame field. With this, our framework enables users to control not only the alignment but also the density and anisotropy of the elements' distribution, resulting in high-quality adaptive quad meshing.
Reflectance scanning
Authors: Chen Guojun , Dong Yue , Peers Pieter , Zhang Jiawan , Tong Xin
Published: July 2014

We present a generalized linear light source solution to estimate both the local shading frame and anisotropic surface reflectance of a planar spatially varying material sample.

We generalize linear light source reflectometry by modulating the intensity along the linear light source, and show that a constant and two sinusoidal lighting patterns are sufficient for estimating the local shading frame and anisotropic surface reflectance. We propose a novel reconstruction algorithm based on the key observation that after factoring out the tangent rotation, the anisotropic surface reflectance lies in a low rank subspace. We exploit the differences in tangent rotation between surface points to infer the low rank subspace and fit each surface point's reflectance function in the projected low rank subspace to the observations. We propose two prototype acquisition devices for capturing surface reflectance that differ on whether the camera is fixed with respect to the linear light source or fixed with respect to the material sample.

We demonstrate convincing results obtained from reflectance scans of surfaces with different reflectance and shading frame variations.
Fast multipole representation of diffusion curves and points
Authors: Sun Timothy , Thamjaroenporn Papoj , Zheng Changxi
Published: July 2014

We propose a new algorithm for random-access evaluation of
diffusion curve images
(DCIs) using the
fast multipole method
. Unlike all previous methods, our algorithm achieves
real-time
performance for rasterization and texture-mapping DCIs of up to millions of curves. After precomputation, computing the color at a single pixel takes nearly constant time. We also incorporate Gaussian radial basis functions into our
fast multipole representation
using the fast Gauss transform. The fast multipole representation is not only a data structure for fast color evaluation, but also a framework for vector graphics analogues of bitmap editing operations. We exhibit this capability by devising new tools for fast diffusion curve Poisson cloning and composition with masks.
An asymptotic numerical method for inverse elastic shape design
Authors: Chen Xiang , Zheng Changxi , Xu Weiwei , Zhou Kun
Published: July 2014

Inverse shape design for elastic objects greatly eases the design efforts by letting users focus on desired target shapes without thinking about elastic deformations. Solving this problem using classic iterative methods (e.g., Newton-Raphson methods), however, often suffers from slow convergence toward a desired solution. In this paper, we propose an asymptotic numerical method that exploits the underlying mathematical structure of specific nonlinear material models, and thus runs orders of magnitude faster than traditional Newton-type methods. We apply this method to compute rest shapes for elastic fabrication, where the rest shape of an elastic object is computed such that after physical fabrication the real object deforms into a desired shape. We illustrate the performance and robustness of our method through a series of elastic fabrication experiments.
DecoBrush
Authors: Lu Jingwan , Barnes Connelly , Wan Connie , Asente Paul , Mech Radomir , Finkelstein Adam
Published: July 2014

Structured decorative patterns are common ornamentations in a variety of media like books, web pages, greeting cards and interior design. Creating such art from scratch using conventional software is time consuming for experts and daunting for novices. We introduce DecoBrush, a data-driven drawing system that generalizes the conventional digital "painting" concept beyond the scope of natural media to allow synthesis of structured decorative patterns following user-sketched paths. The user simply selects an example library and draws the overall shape of a pattern. DecoBrush then synthesizes a shape in the style of the exemplars but roughly matching the overall shape. If the designer wishes to alter the result, DecoBrush also supports user-guided refinement via simple drawing and erasing tools. For a variety of example styles, we demonstrate high-quality user-constrained synthesized patterns that visually resemble the exemplars while exhibiting plausible structural variations.
First-person hyper-lapse videos
Authors: Kopf Johannes , Cohen Michael F. , Szeliski Richard
Published: July 2014

We present a method for converting first-person videos, for example, captured with a helmet camera during activities such as rock climbing or bicycling, into
hyper-lapse
videos, i.e., time-lapse videos with a smoothly moving camera. At high speed-up rates, simple frame sub-sampling coupled with existing video stabilization methods does not work, because the erratic camera shake present in first-person videos is amplified by the speed-up. Our algorithm first reconstructs the 3D input camera path as well as dense, per-frame proxy geometries. We then optimize a novel camera path for the output video that passes near the input cameras while ensuring that the virtual camera looks in directions that can be rendered well from the input. Finally, we generate the novel smoothed, time-lapse video by rendering, stitching, and blending appropriately selected source frames for each output frame. We present a number of results for challenging videos that cannot be processed using traditional techniques.
High-contrast computational caustic design
Authors: Schwartzburg Yuliy , Testuz Romain , Tagliasacchi Andrea , Pauly Mark
Published: July 2014

We present a new algorithm for computational caustic design. Our algorithm solves for the shape of a transparent object such that the refracted light paints a desired caustic image on a receiver screen. We introduce an optimal transport formulation to establish a correspondence between the input geometry and the unknown target shape. A subsequent 3D optimization based on an adaptive discretization scheme then finds the target surface from the correspondence map. Our approach supports
piecewise smooth
surfaces and non-bijective mappings, which eliminates a number of shortcomings of previous methods. This leads to a significantly richer space of caustic images, including smooth transitions, singularities of infinite light density, and completely black areas. We demonstrate the effectiveness of our approach with several simulated and fabricated examples.
Codimensional surface tension flow on simplicial complexes
Authors: Zhu Bo , Quigley Ed , Cong Matthew , Solomon Justin , Fedkiw Ronald
Published: July 2014

Many visually interesting natural phenomena are characterized by thin liquid sheets, long filaments, and droplets. We present a new Lagrangian-based numerical method to simulate these codimensional surface tension driven phenomena using non-manifold simplicial complexes. Tetrahedra, triangles, segments, and points are used to model the fluid volume, thin films, filaments, and droplets, respectively. We present a new method for enforcing fluid incompressibility on simplicial complexes along with a physically-guided meshing algorithm to provide temporally consistent information for interparticle forces. Our method naturally allows for transitions between codimensions, either from tetrahedra to triangles to segments to points or vice versa, regardless of the simulation resolution. We demonstrate the efficacy of this method by simulating various natural phenomena that are characterized by thin fluid sheets, filaments, and surface tension effects.
Intrinsic images in the wild
Authors: Bell Sean , Bala Kavita , Snavely Noah
Published: July 2014

Intrinsic image decomposition separates an image into a reflectance layer and a shading layer. Automatic intrinsic image decomposition remains a significant challenge, particularly for real-world scenes. Advances on this longstanding problem have been spurred by public datasets of ground truth data, such as the MIT Intrinsic Images dataset. However, the difficulty of acquiring ground truth data has meant that such datasets cover a small range of materials and objects. In contrast, real-world scenes contain a rich range of shapes and materials, lit by complex illumination.

In this paper we introduce
Intrinsic Images in the Wild
, a large-scale, public dataset for evaluating intrinsic image decompositions of indoor scenes. We create this benchmark through millions of crowdsourced annotations of relative comparisons of material properties at pairs of points in each scene. Crowdsourcing enables a scalable approach to acquiring a large database, and uses the ability of humans to judge material comparisons, despite variations in illumination. Given our database, we develop a dense CRF-based intrinsic image algorithm for images in the wild that outperforms a range of state-of-the-art intrinsic image algorithms. Intrinsic image decomposition remains a challenging problem; we release our code and database publicly to support future research on this problem, available online at http://intrinsic.cs.cornell.edu/.
AMFS
Authors: Clarberg Petrik , Toth Robert , Hasselgren Jon , Nilsson Jim , Akenine-Möller Tomas
Published: July 2014

We propose a powerful hardware architecture for pixel shading, which enables flexible control of shading rates and automatic shading reuse between triangles in tessellated primitives. The main goal is efficient pixel shading for moderately to finely tessellated geometry, which is not handled well by current GPUs. Our method effectively decouples the cost of pixel shading from the geometric complexity. It thereby enables a wider use of tessellation and fine geometry, even at very limited power budgets. The core idea is to shade over small local grids in parametric patch space, and reuse shading for nearby samples. We also support the decomposition of shaders into multiple parts, which are shaded at different frequencies. Shading rates can be locally and adaptively controlled, in order to direct the computations to visually important areas and to provide performance scaling with a graceful degradation of quality. Another important benefit of shading in patch space is that it allows efficient rendering of distribution effects, which further closes the gap between real-time and offline rendering.
Locally injective parametrization with arbitrary fixed boundaries
Authors: Weber Ofir , Zorin Denis
Published: July 2014

We present an algorithm for mapping a triangle mesh, which is homeomorphic to a disk, to a planar domain with arbitrary fixed boundaries. The algorithm is guaranteed to produce a globally bijective map when the boundary is fixed to a shape that does not self-intersect. Obtaining a one-to-one map is of paramount importance for many graphics applications such as texture mapping. However, for other applications, such as quadrangulation, remeshing, and planar deformations, global bijectively may be unnecessarily constraining and requires significant increase on map distortion. For that reason, our algorithm allows the fixed boundary to intersect itself, and is
guaranteed
to produce a map that is injective locally (if such a map exists). We also extend the basic ideas of the algorithm to support the computation of discrete approximation for extremal quasiconformal maps. The algorithm is conceptually simple and fast. We demonstrate the superior robustness of our algorithm in various settings and configurations in which state-of-the-art algorithms fail to produce injective maps.
Improving the Effectiveness of Testing Pervasive Software via Context Diversity
Authors: Wang Huai , Chan W. K. , Tse T. H.
Published: July 2014

Context-aware pervasive software is responsive to various contexts and their changes. A faulty implementation of the context-aware features may lead to unpredictable behavior with adverse effects. In software testing, one of the most important research issues is to determine the sufficiency of a test suite to verify the software under test. Existing adequacy criteria for testing traditional software, however, have not explored the dimension of serial test inputs and have not considered context changes when constructing test suites. In this article, we define the concept of
context diversity
to capture the extent of context changes in serial inputs and propose three strategies to study how context diversity may improve the effectiveness of the data-flow testing criteria. Our case study shows that the strategy that uses test cases with higher context diversity can significantly improve the effectiveness of existing data-flow testing criteria for context-aware pervasive software. In addition, test suites with higher context diversity are found to execute significantly longer paths, which may provide a clue that reveals why context diversity can contribute to the improvement of effectiveness of test suites.