Volume 34 (2015)

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Designing Camera Networks by Convex Quadratic Programming
(The Eurographics Association and John Wiley & Sons Ltd., 2015) Ghanem, Bernard; Cao, Yuanhao; Wonka, Peter; Olga Sorkine-Hornung and Michael Wimmer
In this paper, we study the problem of automatic camera placement for computer graphics and computer vision applications. We extend the problem formulations of previous work by proposing a novel way to incorporate visibility constraints and camera-to-camera relationships. For example, the placement solution can be encouraged to have cameras that image the same important locations from different viewing directions, which can enable reconstruction and surveillance tasks to perform better. We show that the general camera placement problem can be formulated mathematically as a convex binary quadratic program (BQP) under linear constraints. Moreover, we propose an optimization strategy with a favorable trade-off between speed and solution quality. Our solution is almost as fast as a greedy treatment of the problem, but the quality is significantly higher, so much so that it is comparable to exact solutions that take orders of magnitude more computation time. Because it is computationally attractive, our method also allows users to explore the space of solutions for variations in input parameters. To evaluate its effectiveness, we show a range of 3D results on real-world floorplans (garage, hotel, mall, and airport).
An Efficient Feathering System with Collision Control
(The Eurographics Association and John Wiley & Sons Ltd., 2015) Liu, Le; Li, Xiaosheng; Chen, Yanyun; Liu, Xuehui; Zhang, Jian J.; Wu, Enhua; Stam, Jos and Mitra, Niloy J. and Xu, Kun
We present an efficient interactive system for dressing a naked bird with feathers. In our system, a skeleton associated with guide feathers is used to describe the distribution of the body feathers. The special skeleton can be easily built by the user, given a 3D bird model as input. To address the problem of interpenetrations among feathers, the growth priority between the feather roots is defined, with which we obtain the growth order from a greedily constructed directed acyclic graph. Each feather is then adjusted in that order by a height field based collision resolution process. The height field not only provides an efficient way to detect the collision but also enables us to finely control the degree of collision during feather adjustments. The results show that our approach is capable of resolving the collisions among thousands of feathers in a few seconds. If model animation is desired, the feathers can be adjusted on the fly at interactive framerates. Details of our implementation are provided with several examples to demonstrate the effectiveness of our system.
Fast and Exact (Poisson) Solvers on Symmetric Geometries
(The Eurographics Association and John Wiley & Sons Ltd., 2015) Kazhdan, Misha; Mirela Ben-Chen and Ligang Liu
In computer graphics, numerous geometry processing applications reduce to the solution of a Poisson equation. When considering geometries with symmetry, a natural question to consider is whether and how the symmetry can be leveraged to derive an efficient solver for the underlying system of linear equations. In this work we provide a simple representation-theoretic analysis that demonstrates how symmetries of the geometry translate into block diagonalization of the linear operators and we show how this results in efficient linear solvers for surfaces of revolution with and without angular boundaries.
Guided Mesh Normal Filtering
(The Eurographics Association and John Wiley & Sons Ltd., 2015) Zhang, Wangyu; Deng, Bailin; Zhang, Juyong; Bouaziz, Sofien; Liu, Ligang; Stam, Jos and Mitra, Niloy J. and Xu, Kun
The joint bilateral filter is a variant of the standard bilateral filter, where the range kernel is evaluated using a guidance signal instead of the original signal. It has been successfully applied to various image processing problems, where it provides more flexibility than the standard bilateral filter to achieve high quality results. On the other hand, its success is heavily dependent on the guidance signal, which should ideally provide a robust estimation about the features of the output signal. Such a guidance signal is not always easy to construct. In this paper, we propose a novel mesh normal filtering framework based on the joint bilateral filter, with applications in mesh denoising. Our framework is designed as a two-stage process: first, we apply joint bilateral filtering to the face normals, using a properly constructed normal field as the guidance; afterwards, the vertex positions are updated according to the filtered face normals. We compute the guidance normal on a face using a neighboring patch with the most consistent normal orientations, which provides a reliable estimation of the true normal even with a high-level of noise. The effectiveness of our approach is validated by extensive experimental results.
Hierarchical Multiview Rigid Registration
(The Eurographics Association and John Wiley & Sons Ltd., 2015) Tang, Yizhi; Feng, Jieqing; Mirela Ben-Chen and Ligang Liu
Registration is a key step in the 3D reconstruction of real-world objects. In this paper, we propose a hierarchical method for the rigid registration of multiple views. The multiview registration problem is solved via hierarchical optimization defined on an undirected graph. Each node or edge in this graph represents a single view or a connection between two overlapped views, respectively. The optimizations are performed hierarchically on the edges, the loops, and the entire graph. First, each overlapped pair of views is locally aligned. Then, a loop-based incremental registration algorithm is introduced to refine the initial pairwise alignments. After a loop is registered, the views in the loop are merged into a metaview in the graph. Finally, global error diffusion is applied to the entire graph to evenly distribute the accumulated errors to all views. In addition, a new objective function is defined to describe the loop closure problem; it improves the accuracy and robustness of registration by simultaneously considering transformation and registration errors. The experimental results show that the proposed hierarchical approach is accurate, efficient and robust for initial view states that are not well posed.
Interactive Disassembly Planning for Complex Objects
(The Eurographics Association and John Wiley & Sons Ltd., 2015) Kerbl, Bernhard; Kalkofen, Denis; Steinberger, Markus; Schmalstieg, Dieter; Olga Sorkine-Hornung and Michael Wimmer
We present an approach for the automatic generation, interactive exploration and real-time modification of disassembly procedures for complex, multipartite CAD data sets. In order to lift the performance barriers prohibiting interactive disassembly planning, we run a detailed analysis on the input model to identify recurring part constellations and efficiently determine blocked part motions in parallel on the GPU. Building on the extracted information, we present an interface for computing and editing extensive disassembly sequences in real-time while considering user-defined constraints and avoiding unstable configurations. To evaluate the performance of our C++/CUDA implementation, we use a variety of openly available CAD data sets, ranging from simple to highly complex. In contrast to previous approaches, our work enables interactive disassembly planning for objects which consist of several thousand parts and require cascaded translations during part removal.
Mesh Denoising using Extended ROF Model with L1 Fidelity
(The Eurographics Association and John Wiley & Sons Ltd., 2015) Wu, Xiaoqun; Zheng, Jianmin; Cai, Yiyu; Fu, Chi-Wing; Stam, Jos and Mitra, Niloy J. and Xu, Kun
This paper presents a variational algorithm for feature-preserved mesh denoising. At the heart of the algorithm is a novel variational model composed of three components: fidelity, regularization and fairness, which are specifically designed to have their intuitive roles. In particular, the fidelity is formulated as an L1 data term, which makes the regularization process be less dependent on the exact value of outliers and noise. The regularization is formulated as the total absolute edge-lengthed supplementary angle of the dihedral angle, making the model capable of reconstructing meshes with sharp features. In addition, an augmented Lagrange method is provided to efficiently solve the proposed variational model. Compared to the prior art, the new algorithm has crucial advantages in handling large scale noise, noise along random directions, and different kinds of noise, including random impulsive noise, even in the presence of sharp features. Both visual and quantitative evaluation demonstrates the superiority of the new algorithm.
Stable Topological Signatures for Points on 3D Shapes
(The Eurographics Association and John Wiley & Sons Ltd., 2015) Carrière, Mathieu; Oudot, Steve Y.; Ovsjanikov, Maks; Mirela Ben-Chen and Ligang Liu
Comparing points on 3D shapes is among the fundamental operations in shape analysis. To facilitate this task, a great number of local point signatures or descriptors have been proposed in the past decades. However, the vast majority of these descriptors concentrate on the local geometry of the shape around the point, and thus are insensitive to its connectivity structure. By contrast, several global signatures have been proposed that successfully capture the overall topology of the shape and thus characterize the shape as a whole. In this paper, we propose the first point descriptor that captures the topology structure of the shape as 'seen' from a single point, in a multiscale and provably stable way. We also demonstrate how a large class of topological signatures, including ours, can be mapped to vectors, opening the door to many classical analysis and learning methods. We illustrate the performance of this approach on the problems of supervised shape labeling and shape matching. We show that our signatures provide complementary information to existing ones and allow to achieve better performance with less training data in both applications.
Template Assembly for Detailed Urban Reconstruction
(The Eurographics Association and John Wiley & Sons Ltd., 2015) Nan, Liangliang; Jiang, Caigui; Ghanem, Bernard; Wonka, Peter; Olga Sorkine-Hornung and Michael Wimmer
We propose a new framework to reconstruct building details by automatically assembling 3D templates on coarse textured building models. In a preprocessing step, we generate an initial coarse model to approximate a point cloud computed using Structure from Motion and Multi View Stereo, and we model a set of 3D templates of facade details. Next, we optimize the initial coarse model to enforce consistency between geometry and appearance (texture images). Then, building details are reconstructed by assembling templates on the textured faces of the coarse model. The 3D templates are automatically chosen and located by our optimization-based template assembly algorithm that balances image matching and structural regularity. In the results, we demonstrate how our framework can enrich the details of coarse models using various data sets.

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Browsing Volume 34 (2015) by Subject "and systems"

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