44899292
Subspace gradient domain mesh deformation
In this paper we present a general framework for performing constrained mesh deformation tasks with gradient domain techniques. We present a gradient domain technique that works well with a wide variety of linear and nonlinear constraints. The constraints we introduce include the nonlinear volume constraint for volume preservation, the nonlinear skeleton constraint for maintaining the rigidity of limb segments of articulated figures, and the projection constraint for easy manipulation of the mesh without having to frequently switch between multiple viewpoints. To handle nonlinear constraints, we cast mesh deformation as a nonlinear energy minimization problem and solve the problem using an iterative algorithm. The main challenges in solving this nonlinear problem are the slow convergence and numerical instability of the iterative solver. To address these issues, we develop a subspace technique that builds a coarse control mesh around the original mesh and projects the deformation energy and constraints onto the control mesh vertices using the mean value interpolation. The energy minimization is then carried out in the subspace formed by the control mesh vertices. Running in this subspace, our energy minimization solver is both fast and stable and it provides interactive responses. We demonstrate our deformation constraints and subspace deformation technique with a variety of constrained deformation examples.
8994921
Large mesh deformation using the volumetric graph Laplacian
We present a novel technique for large deformations on 3D meshes using the volumetric graph Laplacian. We first construct a graph representing the volume inside the input mesh. The graph need not form a solid meshing of the input mesh's interior; its edges simply connect nearby points in the volume. This graph's Laplacian encodes volumetric details as the difference between each point in the graph and the average of its neighbors. Preserving these volumetric details during deformation imposes a volumetric constraint that prevents unnatural changes in volume. We also include in the graph points a short distance outside the mesh to avoid local self-intersections. Volumetric detail preservation is represented by a quadric energy function. Minimizing it preserves details in a least-squares sense, distributing error uniformly over the whole deformed mesh. It can also be combined with conventional constraints involving surface positions, details or smoothness, and efficiently minimized by solving a sparse linear system.We apply this technique in a 2D curve-based deformation system allowing novice users to create pleasing deformations with little effort. A novel application of this system is to apply nonrigid and exaggerated deformations of 2D cartoon characters to 3D meshes. We demonstrate our system's potential with several examples.
5676224
All-Frequency Precomputed Radiance Transfer for Glossy Objects
We introduce a method based on precomputed radiance transfer (PRT) that allows interactive rendering of glossy surfaces and includes shadowing effects from dynamic, "all-frequency" lighting. Specifically, source lighting is represented by a cube map at resolution nL = 6 × 32 × 32. We present a novel PRT formulation which factors glossy BRDFs into purely view-dependent and light-dependent parts, achieving reasonable accuracy with only m=10 dimensional factors. We then tabulate an m × nL transfer matrix at each surface vertex as a preprocess, representing the object's response to this lighting. Because this surface signal is so high-dimensional, reducing m is crucial for making practical both the preprocessing and run-time. To compress the transfer matrices, we divide the cube map into 24 lighting segments and apply the Haar wavelet basis in each segment to provide sensible quantization. We also apply clustered principal component analysis (CPCA) to each PRT segment to approximate it as a linear combination of a few (n=16) representative transfer matrices within a small set of clusters over the surface. This exploits spatial coherence to compress very effectively. Most important, it maintains fast rendering rates with 2-3 orders of magnitude more lighting coefficients than previous methods, which increases accuracy and avoids temporal artifacts in high-frequency lighting environments. We demonstrate interactive performance (1-5Hz) on models having up to 50,000 vertices.
2304584
Directional histogram model for three-dimensional shape similarity
In this paper, we propose a novel shape representation we call directional histogram model (DHM). It captures the shape variation of an object and is invariant to scaling and rigid transforms. The DHM is computed by first extracting a directional distribution of thickness histogram signatures, which are translation invariant. We show how the extraction of the thickness histogram distribution can be accelerated using conventional graphics hardware. Orientation invariance is achieved by computing the spherical harmonic transform of this distribution. Extensive experiments show that the DHM is capable of high discrimination power and is robust to noise.
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.
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.
17545097
Design of Rotary Clock Based Circuits
Rotary clock technique has been shown to reduce the power dissipation of clock distribution by up to 80%. However, to our knowledge, no practical digital synchronous circuit has been designed that utilizes the rotary technique due to the multi-phase nature of rotary clock signals and the strong coupling between a rotary clock network and the circuit it drives. In this paper, we make the first attempt to design rotary based circuit by proposing a unified clock and circuit design methodology. Given a sequential circuit and a clock frequency, our scheme derives a rotary clock network and a functionally equivalent circuit so that they can be integrated to operate reliably at the target frequency. We have applied our scheme to design several rotary clock based DSP modules. Simulation results show that all designs operate correctly with no timing violation. Compared with designs using conventional clock trees, our designs achieve an average clock power saving of more than 70%.
11194956
Fuzzy guaranteed cost control for nonlinear systems with time-varying delay
This paper focuses on the problem of guaranteed cost control for Takagi-Sugeno (T-S) fuzzy systems with time-varying delayed state. A linear quadratic cost function is considered as a performance index of the closed-loop fuzzy system. Then, the guaranteed cost control of the closed-loop fuzzy system is discussed, and the sufficient conditions are provided for the construction of a guaranteed cost controller via state feedback and observer-based output feedback. When these conditions, which are given in terms of the feasibility of linear matrix inequalities (LMIs), are satisfied, the designed state feedback controller and observer-based controller gain matrices can be obtained via a convex optimization problem. Two illustrative examples are provided to demonstrate the effectiveness of the approaches proposed in this paper.
11705555
RIP: an efficient hybrid repeater insertion scheme for low power
The paper presents a novel repeater insertion algorithm for interconnect power minimization. The novelty of our approach is in the judicious integration of an analytical solver and a dynamic programming based method. Specifically, the analytical solver chooses a concise repeater library and a small set of repeater location candidates such that the dynamic programming algorithm can be performed fast with little degradation of the solution quality. In comparison with previously reported repeater insertion schemes, within comparable runtimes, our approach achieves up to 37% higher power savings. Moreover, for the same design quality, our scheme attains a speedup of two orders of magnitude.
30635259
On global exponential stability of generalized stochastic neural networks with mixed time-delays
Abstract This paper is concerned with the global exponential stability analysis problem for a general class of stochastic neural networks with mixed time-delays. The mixed time-delays under consideration comprise both the discrete time-varying delays and the distributed time-delays. The main purpose of this paper is to establish easily verifiable conditions under which the delayed stochastic neural network is exponentially stable in the mean square in the presence of both the discrete and distributed delays. By employing a new Lyapunov–Krasovskii functional and conducting stochastic analysis, a linear matrix inequality (LMI) approach is developed to derive the criteria of the exponential stability. Furthermore, the main results are specialized to deal with the analysis problem for the global asymptotic stability within the same LMI framework. The proposed criteria can be readily checked by using some standard numerical packages such as the Matlab LMI toolbox. A simple example is provided to demonstrate the effectiveness and applicability of the proposed testing criteria.
3127291
Repository synchronization in the OAI framework
The Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH) began as an alternative to distributed searching of scholarly e-print repositories. The model embraced by the OAI-PMH is that of metadata harvesting, where value-added services (by a "service provider") are constructed on cached copies of the metadata extracted from the repositories of the harvester's choosing. While this model dispenses with the well-known problems of distributed searching, it introduces the problem of synchronization. Stated simply, this problem arises when the service provider's copy of the metadata does not match the metadata currently at the constituent repositories. We define some metrics for describing the synchronization problem in the OAI-PMH. Based on these metrics, we study the synchronization problem of the OAI-PMH framework and propose several approaches for harvesters to implement better synchronization. In particular, if a repository knows its update frequency, it can publish it in an OAI-PMH identify response using an optional about container that borrows from RDF Site Syndication (RSS) Format.