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8th pacific conference on computer graphics and applications

作者： Sun, HC Metaxas, D Univ Penn VAST Lab Philadelphia PA 19104 USA

ISBN: (纸本)0769508685

This paper presents a data-driven procedural model for the kinematic animation of human walking. The use of data yields realistic looking gait, while the procedural model yields flexibility We present a new motion data representation, the sagittal elevation angles, and present biomechanical evidence that these angles have a stereotyped pattern across many different walking situations, implying their reusability as a motion data source. We also sketch our algorithm for animating human gait based on sagittal elevation angle data which allows us to generate curved locomotion on uneven terrain with stylistic variation without requiring new datasets.

关键词： Computational modeling computer architecture Image processing IP networks Mobile communication Multimedia databases Object oriented modeling Protocols Visualization Web and internet services

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Interpolating and approximating moving frames using B-splines 8

Interpolating and approximating moving frames using B-spline...

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8th pacific conference on computer graphics and applications

作者： Ma, LZ Jiang, ZD Tony, CKY Nanyang Technol Univ Ctr Adv Media Technol Singapore 639798 Singapore

ISBN: (纸本)0769508685

The representation of moving geometry entities is an important issue in the fields of CAD/CAM and robotics motion design. We present a method to interpolate the moving frame homogeneously using B-splines. By analysing the matrix representation of the moving frames, a simplified optimization functional is derived and a recursive iteration method is presented for approximating orthogonal frames at any positions. The error caused by approximation and interpolation is given and shown to be controllable. Since the calculation of moving frames only related with linear equations of two or three unknowns, and the moving frames are approximated with lower degree of polynomial B-spline, the proposed approach can run very fast. The method is useful in motion design and the swept volume representation.

关键词： CADCAM Computational geometry computer aided manufacturing Design automation Equations Error correction Interpolation Optimization methods Robot motion Spline

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Interactive simulation of surgical cuts 8

Interactive simulation of surgical cuts

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8th pacific conference on computer graphics and applications

作者： Bielser, D Gross, MH Swiss Fed Inst Technol Zurich Switzerland

ISBN: (纸本)0769508685

We present a framework for the interactive simulation of surgical cuts such as being practiced in surgical treatment. Unlike most existing methods our framework is based on tetrahedral volume meshes providing mol-e topological flexibility. In order to keep the representation consistent we apply adaptive subdivision schemes dynamically during the simulation. The detection of collisions between the surgical tool and the tissue is accomplished by using an axis aligned bounding box hierarchy which was adapted for deformable objects. For haptic rendering and feedback, we devised a mechanical scalpel model which accounts far the most important interaction forces between scalpel and tissue. The relaxation is computed using a localized, semi-implicit ODE solver: The achieved quality and performance of the presented framework is demonstrated using a human soft tissue model.

关键词： Biological tissues Computational modeling computer simulation Deformable models Equations Feedback Haptic interfaces Humans Solid modeling Surgery

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Approximation with active B-spline curves and surfaces 10

Approximation with active B-spline curves and surfaces

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10th pacific conference on computer graphics and applications

作者： Pottmann, H Leopoldseder, S Hofer, M Vienna Univ Technol Inst Geometry Vienna Austria

ISBN: (纸本)0769517846;0769517854

An active contour model for parametric curve and surface approximation is presented. The active curve or surface adapts to the model shape to be approximated in an optimization algorithm. The quasi-Newton optimization procedure in each iteration step minimizes a quadratic function which is built up with help of local quadratic approximants of the squared distance function of the model shape and an internal energy which has a smoothing and regularization effect. The approach completely avoids the parametrization problem. We also show how to use a similar strategy for the solution of variational problems for curves on surfaces. Examples are the geodesic path connecting two points on a surface and interpolating or approximating spline curves on surfaces. Finally we indicate how the latter topic leads to the variational design of smooth motions which interpolate or approximate given positions.

关键词： Active contours Application software Character generation computer vision Geometry Least squares approximation Parameter estimation Polynomials Smoothing methods Spline

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FEM-based dynamic subdivision splines 8

FEM-based dynamic subdivision splines

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8th pacific conference on computer graphics and applications

作者： Hong, Q SUNY Stony Brook Dept Comp Sci Stony Brook NY 11794 USA

ISBN: (纸本)0769508685

Recent pears have witnessed dramatic growth in the use of subdivision schemes for graphical modeling and animation, especially for the representation of smooth, oftentimes complex shapes of arbitrary topology. Nevertheless, conventional interactive approaches to subdivision objects can be extremely laborious and inefficient. Users must carefully specify the initial mesh and/or painstakingly manipulate the control vertices at different levels of the subdivision hierarchy to satisfy a diverse set of functional requirements and aesthetic criteria in the modeled object. This modeling drawback results from the lack of direct manipulation tools for the limit geometric shape. To improve the efficiency of interactive design, we have developed a unified FEM-based dynamic methodology for arbitrary subdivision schemes by marrying principles of computational physics and finite element analysis with powerful subdivision geometry. Our dynamic framework permits users to directly manipulate the limit surface obtained from any subdivision procedure via simulated "force" tools. Our experiments demonstrate that the new unified FEM-based framework promises a greater potential for subdivision techniques in geometric modeling, finite element analysis, engineering design, computer graphics, and other visual computing applications.

关键词： physics-based modeling geometric modeling computer graphics CAGD subdivision splines deformable models dynamics finite elements interactive techniques

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DStrips: Dynamic triangle strips for real-time mesh simplification and rendering 11

DStrips: Dynamic triangle strips for real-time mesh simplifi...

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11th pacific conference on computer graphics and applications

作者： Shafae, M Pajarola, R Univ Calif Irvine Sch Informat & Comp Sci Comp Graph Lab Irvine CA USA

ISBN: (纸本)0769520286

DStrips is a simple and efficient method to dynamically manage and generate triangle strips for real-time view-dependent multiresolution meshing and rendering. Progressive view-dependent triangle mesh simplification and rendering is an important concept for interactive visualization environments. To minimize the rendering cost, triangle meshes are simplified to the maximal tolerated perceptual error. A further savings can be gained by using hardware optimized rendering primitives such as triangle strips. However, triangle strips have been rarely used successfully in interactive multiresolution meshes due to the costs involved with maintaining the coherency of the strips in the changing mesh. This paper introduces a new dynamic triangle stripping data structure and algorithm, DStrips, that is practical for use with multiresolution meshes. DStrips is aimed at preserving pre-computed triangle strips through changes in the mesh and generating reasonably good triangle strips in real-time. Furthermore, this data structure and algorithm can be easily adapted to any multiresolution mesh which has a face-to-edge/edge-to-face mapping. The presented approach is implemented on top of a real-time view-dependent meshing and rendering framework based on a half-edge data structure using progressive edge collapses and vertex splits. Direct comparisons are made to previous methods in triangle stripification of dynamic and static meshes.

关键词： computer graphics Costs Data structures Geometry Hardware Mesh generation Performance gain Rendering (computer graphics) Strips Visualization

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Deep Video Stabilization Using Adversarial Networks

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computer graphics FORUM 2018年第7期37卷 267-276页

作者： Xu, Sen-Zhe Hu, Jun Wang, Miao Mu, Tai-Jiang Hu, Shi-Min Tsinghua Univ Dept Comp Sci & Technol Beijing Peoples R China

Video stabilization is necessary for many hand-held shot videos. In the past decades, although various video stabilization methods were proposed based on the smoothing of 2D, 2.5D or 3D camera paths, hardly have there been any deep learning methods to solve this problem. Instead of explicitly estimating and smoothing the camera path, we present a novel online deep learning framework to learn the stabilization transformation for each unsteady frame, given historical steady frames. Our network is composed of a generative network with spatial transformer networks embedded in different layers, and generates a stable frame for the incoming unstable frame by computing an appropriate affine transformation. We also introduce an adversarial network to determine the stability of apiece of video. The network is trained directly using the pair of steady and unsteady videos. Experiments show that our method can produce similar results as traditional methods, moreover, it is capable of handling challenging unsteady video of low quality, where traditional methods fail, such as video with heavy noise or multiple exposures. Our method runs in real time, which is much faster than traditional methods.

关键词： CCS Concepts •Computing methodologies → computer graphics

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Feature-based surface light field morphing 11

Feature-based surface light field morphing

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11th pacific conference on computer graphics and applications

作者： Jeong, E Yoon, M Lee, YJ Ahn, M Lee, S Guo, BN Pohang Univ Sci & Technol POSTECH Dept Comp Sci & Engn Pohang 790784 South Korea

ISBN: (纸本)0769520286

A surface light field is a function that gives the colors of each object point viewed from different directions. Object representation with a surface light field provides a nice structure for 3D photography. This paper presents a feature-based morphing technique for two objects equipped with surface light fields. The technique consists of geometry morphing and in-between light field mapping. Geometry morphing is accomplished by 3D mesh morphing, where we introduce a vertex merging technique to generate a simpler metamesh. In in-between light field mapping, an in-between object is rendered by extracting necessary fragments from input surface light fields. We also propose an acceleration technique for rendering an in-between object. Experimental results with real and synthetic data show natural and plausible morphing between objects with surface light fields. The proposed morphing technique can be used as an editing tool for 3D photography.

关键词： Acceleration computer science Data mining Geometry Merging Mesh generation Photography Rendering (computer graphics) Surface texture Visual effects

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TSS BVHs: Tetrahedron Swept Sphere BVHs for Ray Tracing Subdivision Surfaces

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computer graphics FORUM 2016年第7期35卷 279-288页

作者： Du, P. Kim, Y. J. Yoon, S. E. Korea Adv Inst Sci & Technol Daejeon South Korea Hangzhou Dianzi Univ Hangzhou Zhejiang Peoples R China Siemens PLM Software Plano TX USA

We present a novel, compact bounding volume hierarchy, TSS BVH, for ray tracing subdivision surfaces computed by the Catmull-Clark scheme. We use Tetrahedron Swept Sphere (TSS) as a bounding volume to tightly bound limit surfaces of such subdivision surfaces given a user tolerance. Geometric coordinates defining our TSS bounding volumes are implicitly computed from the subdivided mesh via a simple vertex ordering method, and each level of our TSS BVH is associated with a single distance bound, utilizing the Catmull-Clark scheme. These features result in a linear space complexity as a function of the tree depth, while many prior BVHs have exponential space complexity. We have tested our method against different benchmarks with path tracing and photon mapping. We found that our method achieves up to two orders of magnitude of memory reduction with a high culling ratio over the prior AABB BVH methods, when we represent models with two to four subdivision levels. Overall, our method achieves three times performance improvement thanks to these results. These results are acquired by our theorem that rigorously computes our TSS bounding volumes.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.3.7 [computer graphics]: Three-Dimensional graphics and Realism&mdash Raytracing

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Compression of indoor video sequences using homography-based segmentation 8

Compression of indoor video sequences using homography-based...

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8th pacific conference on computer graphics and applications

作者： Park, TJ Fleishman, S Cohen-Or, D Lischinski, D Computer Software Technology Laboratory Electronics and Telecommunications Research Institute South Korea Computer Science Department Tel-Aviv University Israel School of Computer Science and Engineering Hebrew University of Jerusalem Israel

ISBN: (纸本)0769508685

We present a new compression algorithm for video sequences of indoor scenes, or more generally: sequences containing mostly planar and near-planar surfaces. Our approach utilizes edge and optical flow information in order to segment selected keyframes into regions of general shape, such that the motion of each region is predicted well by a planar homography. With this kind of motion prediction, the errors between the predicted intermediate frames and the actual ones are very small, and can be compactly encoded. Our results demonstrate significant improvements in the accuracy of the compressed video sequences, compared to standard general purpose video compression.

关键词： video compression planar homography edge detection image segmentation optical flow motion prediction image-based rendering

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