6032766
A Novel Volume Constrained Smoothing Method for Meshes
In general, mesh smoothing is performed by minimizing the discrete energy function for the surface. One of the major problems in mesh smoothing is to prevent the mesh from shrinking. In this paper, we propose a novel volume constraint to address the shrinking problem in mesh smoothing. Our key observation is that the mesh can be efficiently smoothed patch by patch in a signal processing manner, and then a local volume preserving constraint can be easily imposed to the energy minimization problem associated with the small patch, called the smoothing stencil, so as to effectively avoid the mesh shrinkage. In our implementation, the smoothing stencil is the 1-ring neighboring region of an edge or a triangle. And the constrained minimization problem is solved by a 2-step approximation method for efficiency. A series of examples demonstrate that the proposed smoothing method can be applied to remove noise from a mesh or remove rough detail from an original mesh to generate a smooth model in object reconstruction and geometry modeling.
4392406
Synthesis and rendering of bidirectional texture functions on arbitrary surfaces
The bidirectional texture function (BTF) is a 6D function that describes the appearance of a real-world surface as a function of lighting and viewing directions. The BTF can model the fine-scale shadows, occlusions, and specularities caused by surface mesostructures. We present algorithms for efficient synthesis of BTFs on arbitrary surfaces and for hardware-accelerated rendering. For both synthesis and rendering, a main challenge is handling the large amount of data in a BTF sample. To addresses this challenge, we approximate the BTF sample by a small number of 4D point appearance functions (PAFs) multiplied by 2D geometry maps. The geometry maps and PAFs lead to efficient synthesis and fast rendering of BTFs on arbitrary surfaces. For synthesis, a surface BTF can be generated by applying a texton-based synthesis algorithm to a small set of 2D geometry maps while leaving the companion 4D PAFs untouched. As for rendering, a surface BTF synthesized using geometry maps is well-suited for leveraging the programmable vertex and pixel shaders on the graphics hardware. We present a real-time BTF rendering algorithm that runs at the speed of about 30 frames/second on a mid-level PC with an ATI Radeon 8500 graphics card. We demonstrate the effectiveness of our synthesis and rendering algorithms using both real and synthetic BTF samples.
7819313
Constrained Fairing for Meshes
In this paper, we present a novel fairing algorithm for the removal of noise from uniform triangular meshes without shrinkage and serious distortion. The key feature of this algorithm is to keep all triangle centers invariant at each smoothing step by including some constraints in the energy minimization functional. The constrained functional is then minimized efficiently using an iterative method. Further, we apply this smoothing technique to a multiresolution representation to remove arbitrary levels of detail. A volume-preserving decimation algorithm is presented to generate the multiresolution representation. The experimental results demonstrate the combined algorithm's stability and efficiency.
11755901
Interactive mesh deformation with pseudo material effects
This paper presents a novel interactive mesh deformation method that can achieve various dynamic material effects, including elastic membrane and cloth effects. In our framework, a mesh is encoded by some differential quantities based on edge length and dihedral angle; and the deformation is formulated as a least square problem for preserving the edge length and dihedral angle via the differential quantities. In order to obtain anisotropic material effects, we further propose an edge-weighting scheme based on a user-specified vector field. To avoid specifying the local transformations, we set up an iterative scheme for solving the deformation. At last, several examples are presented to show that our approach can interactively generate visually pleasing deformations. Copyright © 2006 John Wiley & Sons, Ltd.
737878
Bi-scale radiance transfer
Radiance transfer represents how generic source lighting is shadowed and scattered by an object to produce view-dependent appearance. We generalize by rendering transfer at two scales. A macro-scale is coarsely sampled over an object's surface, providing global effects like shadows cast from an arm onto a body. A meso-scale is finely sampled over a small patch to provide local texture. Low-order (25D) spherical harmonics represent low-frequency lighting dependence for both scales. To render, a coefficient vector representing distant source lighting is first transformed at the macro-scale by a matrix at each vertex of a coarse mesh. The resulting vectors represent a spatially-varying hemisphere of lighting incident to the meso-scale. A 4D function, called a radiance transfer texture (RTT), then specifies the surface's meso-scale response to each lighting basis component, as a function of a spatial index and a view direction. Finally, a 25D dot product of the macro-scale result vector with the vector looked up from the RTT performs the correct shading integral. We use an id map to place RTT samples from a small patch over the entire object; only two scalars are specified at high spatial resolution. Results show that bi-scale decomposition makes preprocessing practical and efficiently renders self-shadowing and interreflection effects from dynamic, low-frequency light sources at both scales.
16862069
Progressive geometry compression for meshes
A novel progressive geometry compression scheme is presented in this paper. In this scheme, a mesh is represented as a base mesh followed by some groups of vertex split operations using an improved simplification method in which each level of the mesh can be refined into the next level by carrying out a group of vertex split operations in any order. Consequently, the progressive mesh (PM) representation can be effectively encoded by permuting the vertex split operations in each group. Meanwhile, a geometry predictor using the Laplacian operator is designed to predict each new vertex position using its neighbours. The correction is quantized and encoded using a Huffman coding scheme. Experimental results show that our algorithm obtains higher compression ratios than previous work. It is very suitable for the progressive transmission of geometric models over the Internet.
426496
Freeze: engineering a fast repeater insertion solver for power minimization using the ellipsoid method
This paper presents a novel repeater insertion algorithm for the power minimization of realistic interconnect trees under given timing budgets. Our algorithm judiciously combines a local optimizer based on the dynamic programming technique and a global search engine using the ellipsoid method. As a result, our approach is capable of producing high-quality solutions at a very fast speed. Furthermore, our scheme is robust and does not need any manual tuning of the iteration-control parameters. We have developed a repeater insertion tool, called Freeze, using the proposed algorithm and applied it to various interconnect trees with different timing targets. Experimental results demonstrate the high effectiveness of our approach. In comparison with the state-of-the-art low-power repeater insertion schemes, Freeze requires 5.8 times fewer iterations on the average, achieving up to 27 times speedup with even better power savings. When compared with a dynamic programming based scheme, which guarantees the optimal solution, our tool delivers up to 50 times speedup with 0.9% power increase on the average.
41671130
Accelerated backward warping
In this paper a plane-based backward warping algorithm is proposed to generate novel views from multiple reference images. first, depth information is employed to reconstruct space planes from individual reference images and calculate the potential occluding relationship between these planes. Then the planes which represent each identical space plane from different reference images are compared with each other to decide the one with the best sample rate to be preserved and used in the later warping period while the other samples are abandoned. While the image of a novel view is produced, traditional methods in computer graphics, such as visibility test and clipping, are used to process the planes reconstructed. Then the planes processed are projected onto the desired image from the knowledge on which plane the desired image pixels are warped from can be acquired. Finally, pixels' depth of the desired image is calculated and then a backward warping is performed from these pixels to the reference images to obtain their colors. The storage requirement in the algorithm is small and increases slowly with the number of reference images increases. By combining the strategy of only preserving the best sample parts and the backward warping algorithm, the sample problem could be well tackled.
15430727
Towards Service Discovery and Subscription based on Community-of-Interest
Current service discovery and subscription are "provider-centric " indeed, which costs the consumers too many efforts and makes the wide spectrum of QoS hard to use. In this position paper, we propose a "consumer-centric" service discovery and subscription approach. The core idea is derived from the "community-of-interest (CoI)" concept, which means the services with same or similar functionalities can form a community of the consumer's interest. This approach facilitates the consumers in three ways. Firstly, it simplifies the service discovery for the consumers who can "purely" care about the functionality and qualities instead of the providers. Secondly, it optimizes the service subscription for the consumers who just subscribe the CoI instead of a single and monolithic service provider while the COI takes charge of matching and scheduling the "best-of-breed" service automatically. Thirdly, it incarnates the wide spectrum of QoS to the consumers who will face with all possible QoS supported by the services in the CoI. The supporting framework is discussed and some key technical issues are demonstrated
62445228
Practical repeater insertion for low power: what repeater library do we need?
This paper investigates the problem of repeater insertion for low power under a given timing budget. A novel repeater insertion algorithm is proposed to compute the optimal repeater number and width in the discrete solution space, as defined by a given repeater library. Using the proposed algorithm, two practical and highly important questions are addressed. Given a certain tolerance to the degradation of repeater power dissipation: 1) how coarse could the repeater size granularity be? 2) What range should repeater widths be in? The experimental results provide valuable insights into repeater library design. Specifically, the investigation reveals that coarse repeater size granularities can be used to reduce the library size by more than 87% with merely a 4% power degradation. Moreover, for two-pin interconnects with various wire lengths and timing targets, the range of optimal repeater sizes for low power is limited, indicating that a low-cost small-size repeater library, if well designed, is adequate to provide high-quality repeater insertion solutions. The proposed scheme can be used in early design stages to generate a compact repeater library that is passed on to other repeater insertion algorithms.
368408
A framework for opportunistic scheduling in wireless networks
Abstract We present a method, called opportunistic scheduling, for exploiting the time-varying nature of the radio environment to increase the overall performance of the system under certain quality of service/fairness requirements of users. We first introduce a general framework for opportunistic scheduling, and then identify three general categories of scheduling problems under this framework. We provide optimal solutions for each of these scheduling problems. All the proposed scheduling policies are implementable online; we provide parameter estimation algorithms and implementation procedures for them. We also show how previous work by us and others directly fits into or is related to this framework. We demonstrate via simulation that opportunistic scheduling schemes result in significant performance improvement compared with non-opportunistic alternatives.