27-Issue 7

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https://diglib.eg.org/handle/10.2312/140

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    A Hidden-picture Puzzles Generator
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Yoon, Jong-Chul; Lee, In-Kwon; Kang, Henry
    A hidden-picture puzzle contains objects hidden in a background image, in such a way that each object fits closely into a local region of the background. Our system converts image of the background and objects into line drawing, and then finds places in which to hide transformed versions of the objects using rotation-invariant shape context matching. During the hiding process, each object is subjected to a slight deformation to enhance its similarity to the background. The results were assessed by a panel of puzzle-solvers.
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    Reconstructing head models from photographs for individualized 3D-audio processing
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Dellepiane, M.; Pietroni, N.; Tsingos, N.; Asselot, M.; Scopigno, R.
    Visual fidelity and interactivity are the main goals in Computer Graphics research, but recently also audio is assuming an important role. Binaural rendering can provide extremely pleasing and realistic three-dimensional sound, but to achieve best results it s necessary either to measure or to estimate individual Head Related Transfer Function (HRTF). This function is strictly related to the peculiar features of ears and face of the listener. Recent sound scattering simulation techniques can calculate HRTF starting from an accurate 3D model of a human head. Hence, the use of binaural rendering on large scale (i.e. video games, entertainment) could depend on the possibility to produce a sufficiently accurate 3D model of a human head, starting from the smallest possible input. In this paper we present a completely automatic system, which produces a 3D model of a head starting from simple input data (five photos and some key-points indicated by user). The geometry is generated by extracting information from images and accordingly deforming a 3D dummy to reproduce user head features. The system proves to be fast, automatic, robust and reliable: geometric validation and preliminary assessments show that it can be accurate enough for HRTF calculation.
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    Gradient-based Interpolation and Sampling for Real-time Rendering of Inhomogeneous, Single-scattering Media
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Ren, Zhong; Zhou, Kun; Lin, Stephen; Guo, Baining
    We present a real-time rendering algorithm for inhomogeneous, single scattering media, where all-frequency shading effects such as glows, light shafts, and volumetric shadows can all be captured. The algorithm first computes source radiance at a small number of sample points in the medium, then interpolates these values at other points in the volume using a gradient-based scheme that is efficiently applied by sample splatting. The sample points are dynamically determined based on a recursive sample splitting procedure that adapts the number and locations of sample points for accurate and efficient reproduction of shading variations in the medium. The entire pipeline can be easily implemented on the GPU to achieve real-time performance for dynamic lighting and scenes. Rendering results of our method are shown to be comparable to those from ray tracing.
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    Photon-driven Irradiance Cache
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Brouillat, J.; Gautron, P.; Bouatouch, K.
    We describe a global illumination method combining two well known techniques: photon mapping and irradiance caching. The photon mapping method has the advantage of being view independent but requires a costly additional rendering pass, called final gathering. As for irradiance caching, it is view-dependent, irradiance is only computed and cached on surfaces of the scene as viewed by a single camera. To compute records covering the entire scene, the irradiance caching method has to be run for many cameras, which takes a long time and is a tedious task since the user has to place the needed cameras manually. Our method exploits the advantages of these two methods and avoids any intervention of the user. It computes a refined, view-independent irradiance cache from a photon map. The global illumination solution is then rendered interactively using radiance cache splatting.
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    Interactive Global Illumination for Deformable Geometry in CUDA
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Schmitz, Arne; Tavenrath, Markus; Kobbelt, Leif
    Interactive global illumination for fully deformable scenes with dynamic relighting is currently a very elusive goal in the area of realistic rendering. In this work we propose a system that is based on explicit visibility calculations and which is highly efficient and scalable. The rendering equation defines the light exchange between surfaces, which we approximate by subsampling. By utilizing the power of modern parallel GPUs using the CUDA framework we achieve interactive frame rates. Since we update the global illumination continuously in an asynchronous fashion, we maintain interactivity at all times for moderately complex scenes. We show that we can achieve higher frame rates for scenes with moving light sources, diffuse indirect illumination and dynamic geometry than other current methods, while maintaining a high image quality.
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    The Craniofacial Reconstruction from the Local Structural Diversity of Skulls
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Pei, Yuru; Zha, Hongbin; Yuan, Zhongbiao
    The craniofacial reconstruction is employed as an initialization of the identification from skulls in forensics. In this paper, we present a two-level craniofacial reconstruction framework based on the local structural diversity of the skulls. On the low level, the holistic reconstruction is formulated as the superimposition of the selected tissue map on the novel skull. The crux is the accurate map registration, which is implemented as a warping guided by the 2D feature curve patterns. The curve pattern extraction under an energy minimization framework is proposed for the automatic feature labeling on the skull depth map. The feature configuration on the warped tissue map is expected to resemble that on the novel skull. In order to make the reconstructed faces personalized, on the high level, the local facial features are estimated from the skull measurements via a RBF model. The RBF model is learnt from a dataset of the skull and the face feature pairs extracted from the head volume data. The experiments demonstrate the facial outlooks can be reconstructed feasibly and efficiently.
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    Interactive Glossy Reflections using GPU-based Ray Tracing with Adaptive LOD
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Yu, Xuan; Wang, Rui; Yu, Jingyi
    We present an interactive GPU-based algorithm for accurately rendering high-quality, dynamic glossy reflection effects from both HDR environment maps and local scene objects. Our method uses hardware rasterization to produce primary pixels, and GPU-based BRDF importance sampling [CK07] to quickly generate reflected rays. We utilize a fast GPU ray tracer proposed by Carr et al. [CHCH06] to compute reflection hits. Our main contribution is an adaptive level-of-detail (LOD) control algorithm that greatly improves ray tracing performance during reflection shading. Specifically, we use the solid angle represented by each reflected ray to adaptively pick the level of termination in the BVH traversal step during ray tracing. This leads to 2 - 3x speedup over an unmodified implementation of [CHCH06]. Based on the same solid angle measure, we derive a texture filtering formula to reduce reflection aliasing artifacts, taking advantage of hardware MIP mapping. This extends the filtering algorithm presented in [CK07] from environment mapping to local scene reflection. Using our algorithm, we demonstrate interactive rendering rates for several scenes featuring dynamic lighting and material changes, spatially varying BRDF parameters, and rigid-body object movement.
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    A Resolution Independent Approach for the Accurate Rendering of Grooved Surfaces
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Bosch, C.; Pueyo, X.; Merillou, S.; Ghazanfarpour, D.
    This paper presents a method for the accurate rendering of path-based surface details such as grooves, scratches and similar features. The method is based on a continuous representation of the features in texture space, and the rendering is performed by means of two approaches: one for isolated or non-intersecting grooves and another for special situations like intersections or ends. The proposed solutions perform correct antialiasing and take into account visibility and inter-reflections with little computational effort and memory requirements. Compared to anisotropic BRDFs and scratch models, we have no limitations on the distribution of grooves over the surface or their geometry, thus allowing more general patterns. Compared to displacement mapping techniques, we can efficiently simulate features of all sizes without requiring additional geometry or multiple representations.
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    Shape-simplifying Image Abstraction
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Kang, Henry; Lee, Seungyong
    This paper presents a simple algorithm for producing stylistic abstraction of a photograph. Based on mean curvature flow in conjunction with shock filter, our method simplifies both shapes and colors simultaneously while preserving important features. In particular, we develop a constrained mean curvature flow, which outperforms the original mean curvature flow in conveying the directionality of features and shape boundaries. The proposed algorithm is iterative and incremental, and therefore the level of abstraction is intuitively controlled. Optionally, simple user masking can be incorporated into the algorithm to selectively control the abstraction speed and to protect particular regions. Experimental results show that our method effectively produces highly abstract yet feature-preserving illustrations from photographs.
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    Patch-type Segmentation of Voxel Shapes using Simplified Surface Skeletons
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Reniers, Dennie; Telea, Alexandru
    We present a new method for decomposing a 3D voxel shape into disjoint segments using the shape s simplified surface-skeleton. The surface skeleton of a shape consists of 2D manifolds inside its volume. Each skeleton point has a maximally inscribed ball that touches the boundary in at least two contact points. A key observation is that the boundaries of the simplified fore- and background skeletons map one-to-one to increasingly fuzzy, soft convex, respectively concave, edges of the shape. Using this property, we build a method for segmentation of 3D shapes which has several desirable properties. Our method segments both noisy shapes and shapes with soft edges which vanish over low-curvature regions. Multiscale segmentations can be obtained by varying the simplification level of the skeleton. We present a voxel-based implementation of our approach and illustrate it on several realistic examples.
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    Shrinkability Maps for Content-Aware Video Resizing
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Zhang, Yi-Fei; Hu, Shi-Min; Martin, Ralph R.
    A novel method is given for content-aware video resizing, i.e. targeting video to a new resolution (which may involve aspect ratio change) from the original.We precompute a per-pixel cumulative shrinkability map which takes into account both the importance of each pixel and the need for continuity in the resized result. (If both x and y resizing are required, two separate shrinkability maps are used, otherwise one suffices). A random walk model is used for efficient offline computation of the shrinkability maps. The latter are stored with the video to create a multi-sized video, which permits arbitrary-sized new versions of the video to be later very efficiently created in real-time, e.g. by a video-on-demand server supplying video streams to multiple devices with different resolutions. These shrinkability maps are highly compressible, so the resulting multi-sized videos are typically less than three times the size of the original compressed video. A scaling function operates on the multi-sized video, to give the new pixel locations in the result, giving a high-quality content-aware resized video.Despite the great efficiency and low storage requirements for our method, we produce results of comparable quality to state-of-the-art methods for content-aware image and video resizing.
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    A Prism-Free Method for Silhouette Rendering in Inverse Displacement Mapping
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Chen, Ying-Chieh; Chang, Chun-Fa
    Silhouette is a key feature that distinguishes displacement mapping from normal mapping. However the silhouette rendering in the GPU implementation of displacement mapping (which is often called inversed displacement mapping) is tricky. Previous approaches rely mostly on construction of additional extruding prism-like geometry, which slows down the rendering significantly. In this paper, we proposed a method for solving the silhouette rendering problem in inverse displace mapping without using any extruding prism-like geometry. At each step of intersection finding, we continuously bends the viewing ray according to the current local tangent space associated with the surface. Thus, it allows mapping a displacement map onto an arbitrary curved surface with more accurate silhouette. While our method is simple, it offers surprisingly good results over Curved Relief Map (CRM) [OP05] in many difficult or degenerated cases.
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    Sketching MLS Image Deformations On the GPU
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Weng, Yanlin; Shi, Xiaohan; Bao, Hujun; Zhang, Jun
    In this paper, we present an image editing tool that allows the user to deform images using a sketch-based interface. The user simply sketches a set of source curves in the input image, and also some target curves that the source curves should be deformed to. Then the moving least squares (MLS) deformation technique [SMW06] is adapted to produce realistic deformations while satisfying the curves positional constraints. We also propose a scheme to reduce image fold-overs in MLS deformations. Our system has a very intuitive user interface, generates physically plausible deformations, and can be easily implemented on the GPU for real-time performance.
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    Part-type Segmentation of Articulated Voxel-Shapes using the Junction Rule
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Reniers, Dennie; Telea, Alexandru
    We present a part-type segmentation method for articulated voxel-shapes based on curve skeletons. Shapes are considered to consist of several simpler, intersecting shapes. Our method is based on the junction rule: the observation that two intersecting shapes generate an additional junction in their joined curve-skeleton near the place of intersection. For each curve-skeleton point, we construct a piecewise-geodesic loop on the shape surface. Starting from the junctions, we search along the curve skeleton for points whose associated loops make for suitable part cuts. The segmentations are robust to noise and discretization artifacts, because the curve skeletonization incorporates a single user-parameter to filter spurious curve-skeleton branches. Furthermore, segment borders are smooth and minimally twisting by construction. We demonstrate our method on several real-world examples and compare it to existing part-type segmentation methods.
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    Knitting a 3D Model
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Igarashi, Yuki; Igarashi, Takeo; Suzuki, Hiromasa
    A knitted animal is made of a closed surface consisting of several knitted patches knitted out of yarn and stuffed with cotton (Fig. 1). We introduce a system to create a knitting pattern from a given 3D surface model (mainly designed for rotund animal models). A knitting pattern is an instructional diagram describing how to knit yarn to obtain a desired shape. Since the creation of knitting patterns requires special skill, this is difficult for nonprofessionals. Our system automates the process and allows anyone to obtain his or her original knitting patterns from a 3D model. The system first covers the surface of the model with parallel winding strips of constant width. The system then samples the strip at constant intervals to convert it into a knitting pattern. The result is presented in a standard visual format so that the user can easily refer it during actual knitting. We show several examples of knitted animals created using the system.1Example of a knitted animal. A typical knitted animal consists of several circular and cylindrical patches.
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    Progressive Interpolation based on Catmull-Clark Subdivision Surfaces
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Chen, Zhongxian; Luo, Xiaonan; Tan, Le; Ye, Binghong; Chen, Jiapeng
    We introduce a scheme for constructing a Catmull-Clark subdivision surface that interpolates the vertices of a quadrilateral mesh with arbitrary topology. The basic idea here is to progressively modify the vertices of an original mesh to generate a new control mesh whose limit surface interpolates all vertices in the original mesh. The scheme is applicable to meshes with any size and any topology, and it has the advantages of both a local scheme and a global scheme.
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    Capturing Intention-based Full-Frame Video Stabilization
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Chen, Bing-Yu; Lee, Ken-Yi; Huang, Wei-Ting; Lin, Jong-Shan
    Annoying shaky motion is one of the significant problems in home videos, since hand shake is an unavoidable effect when capturing by using a hand-held camcorder. Video stabilization is an important technique to solve this problem, but the stabilized videos resulting from some current methods usually have decreased resolution and are still not so stable. In this paper, we propose a robust and practical method of full-frame video stabilization while considering user s capturing intention to remove not only the high frequency shaky motions but also the low frequency unexpected movements. To guess the user s capturing intention, we first consider the regions of interest in the video to estimate which regions or objects the user wants to capture, and then use a polyline to estimate a new stable camcorder motion path while avoiding the user s interested regions or objects being cut out. Then, we fill the dynamic and static missing areas caused by frame alignment from other frames to keep the same resolution and quality as the original video. Furthermore, we smooth the discontinuous regions by using a three-dimensional Poisson-based method. After the above automatic operations, a full-frame stabilized video can be achieved and the important regions and objects can also be preserved.
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    View and Time Interpolation in Image Space
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Stich, Timo; Linz, Christian; Albuquerque, Georgia; Magnor, Marcus
    The ability to interpolate between images taken at different time and viewpoints directly in image space opens up new possiblities. The goal of our work is to create plausible in-between images in real time without the need for an intermediate 3D reconstruction. This enables us to also interpolate between images recorded with uncalibrated and unsynchronized cameras. In our approach we use a novel discontiniuity preserving image deformation model to robustly estimate dense correspondences based on local homographies. Once correspondences have been computed we are able to render plausible in-between images in real time while properly handling occlusions. We discuss the relation of our approach to human motion perception and other image interpolation techniques.
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    Real-Time Depth-of-Field Rendering Using Point Splatting on Per-Pixel Layers
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Lee, Sungkil; Kim, Gerard Jounghyun; Choi, Seungmoon
    We present a real-time method for rendering a depth-of-field effect based on the per-pixel layered splatting where source pixels are scattered on one of the three layers of a destination pixel. In addition, the missing information behind foreground objects is filled with an additional image of the areas occluded by nearer objects. The method creates high-quality depth-of-field results even in the presence of partial occlusion, without major artifacts often present in the previous real-time methods. The method can also be applied to simulating defocused highlights. The entire framework is accelerated by GPU, enabling real-time post-processing for both off-line and interactive applications.
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    A Biorthogonal Wavelet Approach based on Dual Subdivision
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Zhang, Hui; Qin, Guiming; Qin, Kaihuai; Sun, Hanqiu
    In this paper a biorthogonal wavelet approach based on Doo-Sabin subdivision is presented. In the dual subdivision like Doo-Sabin scheme, all the old control vertices disappear after one subdivision step, which is a big challenge to the biorthogonal wavelet construction. In our approach, the barycenters of the V-faces corresponding to the old vertices are selected as the vertices associated with the scaling functions to construct the scaling space. The lifting scheme is used to guarantee the fitting quality of the wavelet transform, and a local orthogonalization is introduced with a discrete inner product operation to improve the computation efficiency. Sharp feature modeling based on extended Doo-Sabin subdivision rules is also discussed in the framework of our wavelet construction. The presented wavelet construction is proven to be stable and effective by the experimental results.