27-Issue 7

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

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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.
Automatic Facsimile of Chinese Calligraphic Writings
(The Eurographics Association and Blackwell Publishing Ltd, 2008) Xu, Songhua; Jiang, Hao; Jin, Tao; Lau, Francis C.M.; Pan, Yunhe
Reconstructing 3D Shape, Albedo and Illumination from a Single Face Image
(The Eurographics Association and Blackwell Publishing Ltd, 2008) Wang, S. F.; Lai, S. H.
The morphable model has been employed to efficiently describe 3D face shape and the associated albedo with a reduced set of basis vectors. The spherical harmonics (SH) model provides a compact basis to well approximate the image appearance of a Lambertian object under different illumination conditions. Recently, the SH and morphable models have been integrated for 3D face shape reconstruction. However, the reconstructed 3D shape is either inconsistent with the SH bases or obtained just from landmarks only. In this work, we propose a geometrically consistent algorithm to reconstruct the 3D face shape and the associated albedo from a single face image iteratively by combining the morphable model and the SH model. The reconstructed 3D face geometry can uniquely determine the SH bases, therefore the optimal 3D face model can be obtained by minimizing the error between the input face image and a linear combination of the associated SH bases. In this way, we are able to preserve the consistency between the 3D geometry and the SH model, thus refining the 3D shape reconstruction recursively. Furthermore, we present a novel approach to recover the illumination condition from the estimated weighting vector for the SH bases in a constrained optimization formulation independent of the 3D geometry. Experimental results show the effectiveness and accuracy of the proposed face reconstruction and illumination estimation algorithm under different face poses and multiple-light-source illumination conditions.
Interpolatory and Mixed Loop Schemes
(The Eurographics Association and Blackwell Publishing Ltd, 2008) Shi, Zhuo; Lin, Shujin; Luo, Xiaonan; Wang, Renhong
This paper presents a new interpolatory Loop scheme and an unified and mixed interpolatory and approximation subdivision scheme for triangular meshes. The former which is C1 continuous as same as the modified Butterfly scheme has better effect in some complex models. The latter can be used to solve the popping effect problem when switching between meshes at different levels of resolution. The scheme generates surfaces coincident with the Loop subdivision scheme in the limit condition having the coefficient k equal 0. When k equal 1, it will be changed into a new interpolatory subdivision scheme. Eigen-structure analysis demonstrates that subdivision surfaces generated using the new scheme are C1 continuous. All these are achieved only by changing the value of a parameter k. The method is a completely simple one without constructing and solving equations. It can achieve local interpolation and solve the popping effect problem which are the method s advantages over the modified Butterfly scheme.
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.
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.
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.
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.
Distortion Optimization based Image Completion from a Large Displacement View
(The Eurographics Association and Blackwell Publishing Ltd, 2008) Liu, Chunxiao; Yang, Yingzhen; Peng, Qunsheng; Wang, Jin; Chen, Wei
We present a new image completion method based on an additional large displacement view (LDV) of the same scene for faithfully repairing large missing regions on the target image in an automatic way. A coarse-to-fine distortion correction algorithm is proposed to minimize the perspective distortion in the corresponding parts for the common scene regions on the LDV image. First, under the assumption of a planar scene, the LDV image is warped according to a homography to generate the initial correction result. Second, the residual distortions in the common known scene regions are revealed by means of a mismatch detection mechanism and relaxed by energy optimization of overlap correspondences, with the expectations of color constancy and displacement field smoothness. The fundamental matrix for the two views is then computed based on the reliable correspondence set. Third, under the constraints of epipolar geometry, displacement field smoothness and color consistency of the neighboring pixels, the missing pixels are orderly restored according to a specially defined repairing priority function. We finally eliminate the ghost effect between the repaired region and its surroundings by Poisson image blending. Experimental results demonstrate that our method outperforms recent state-of-the-art image completion methods for repairing large missing area with complex structure information.
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.
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.
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.
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.
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.
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.
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.
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.
Caustic Forecasting: Unbiased Estimation of Caustic Lighting for Global Illumination
(The Eurographics Association and Blackwell Publishing Ltd, 2008) Budge, B. C.; Anderson, J. C.; Joy, K. I.
We present an unbiased method for generating caustic lighting using importance sampled Path Tracing with Caustic Forecasting. Our technique is part of a straightforward rendering scheme which extends the Illumination by Weak Singularities method to allow for fully unbiased global illumination with rapid convergence. A photon shooting preprocess, similar to that used in Photon Mapping, generates photons that interact with specular geometry. These photons are then clustered, effectively dividing the scene into regions which will contribute similar amounts of caustic lighting to the image. Finally, the photons are stored into spatial data structures associated with each cluster, and the clusters themselves are organized into a spatial data structure for fast searching. During rendering we use clusters to decide the caustic energy importance of a region, and use the local photons to aid in importance sampling, effectively reducing the number of samples required to capture caustic lighting.
Local Volume Preservation for Skinned Characters
(The Eurographics Association and Blackwell Publishing Ltd, 2008) Rohmer, Damien; Hahmann, Stefanie; Cani, Marie-Paule
Generating plausible deformations of a character skin within the standard production pipeline is a challenge. This paper presents a volume preservation method dedicated to skinned characters. As usual, the character is defined by a skin mesh at some rest pose and an animation skeleton. At each animation step, skin deformations are first computed using standard SSD. Our method corrects the result using a set of local deformations which model the fold-over-free, constant volume behavior of soft tissues. This is done geometrically, without the need of any physically-based simulation. To make the method easily applicable, we also provide automatic ways to extract the local regions where volume is to be preserved and to compute adequate skinning weights, both based on the character s morphology.
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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