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10th pacific conference on computer graphics and applications

作者： Zhang, YC Liu, XH Wu, EH Chinese Acad Sci Inst Software Key Lab Comp Sci Beijing 100864 Peoples R China

ISBN: (纸本)0769517846;0769517854

In this paper, a hybrid representation of environment models by a combination of points and polygons is proposed. Through the model, a real time walkthrough of a complex environment can be achieved. We start from multiple depth reference images and classify the pixels of images into two categories, corresponding respectively to the planar and non-planar surfaces in 3D space, then all the redundant points are removed by a comparison algorithm of sampling rate. For the pixels corresponding to the non-planar surfaces, the point representation is maintained, and a local reconstruction and resampling process is employed to re-sample a set of points that distribute more uniformly on the surfaces. The points re-sampled are organized by OBB-tree according to their space coordinates and a multiresolution structure is built to improve the rendering efficiency. For the pixels corresponding to the planar surfaces, the plane coefficients are reconstructed and all their appearances in the reference images are merged to texture maps. Under this hybrid representation, texture mapping and point-based rendering are employed to render the novel views, to take full advantage of the acceleration utility of graphics hardware. The algorithm demonstrates the combined advantages of the approaches in traditional computer graphics and PBR/IBR, the texture mapping for plane surfaces and the point-based rendering for high detail surfaces and shapes.

关键词： Acceleration Bioreactors computer graphics Hardware Image reconstruction Image sampling Pixel Rendering (computer graphics) Surface reconstruction Surface texture

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Pixel History Linear Models for Real-Time Temporal Filtering

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computer graphics FORUM 2016年第7期35卷 363-372页

作者： Iglesias-Guitian, Jose A. Moon, Bochang Koniaris, Charalampos Smolikowski, Eric Mitchell, Kenny Disney Res Zurich Switzerland Walt Disney Imagineering Glendale CA USA

We propose a new real-time temporal filtering and antialiasing (AA) method for rasterization graphics pipelines. Our method is based on Pixel History Linear Models (PHLM), a new concept for modeling the history of pixel shading values over time using linear models. Based on PHLM, our method can predict per-pixel variations of the shading function between consecutive frames. This combines temporal reprojection with per-pixel shading predictions in order to provide temporally coherent shading, even in the presence of very noisy input images. Our method can address both spatial and temporal aliasing problems under a unique filtering framework that minimizes filtering error through a recursive least squares algorithm. We demonstrate our method working with a commercial deferred shading engine for rasterization and with our own OpenGL deferred shading renderer. We have implemented our method in GPU and it has shown significant reduction of temporal flicker in very challenging scenarios including foliage rendering, complex non-linear camera motions, dynamic lighting, reflections, shadows and fine geometric details. Our approach, based on PHLM, avoids the creation of visible ghosting artifacts and it reduces the filtering overblur characteristic of temporal deflickering methods. At the same time, the results are comparable to state-of-the-art realtime filters in terms of temporal coherence.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.4.3 [computer graphics]: Enhancement&mdash Filtering I.3.3 [computer graphics]: Picture/Image Generation&mdash Antialiasing

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An Error Estimation Framework for Many-Light Rendering

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computer graphics FORUM 2016年第7期35卷 431-439页

作者： Nabata, K. Iwasaki, K. Dobashi, Y. Nishita, T. Wakayama Univ Wakayama Japan Hokkaido Univ Sapporo Hokkaido Japan UEI Res Tokyo Japan Hiroshima Shudo Univ Hiroshima Japan

The popularity of many-light rendering, which converts complex global illumination computations into a simple sum of the illumination from virtual point lights (VPLs), for predictive rendering has increased in recent years. A huge number of VPLs are usually required for predictive rendering at the cost of extensive computational time. While previous methods can achieve significant speedup by clustering VPLs, none of these previous methods can estimate the total errors due to clustering. This drawback imposes on users tedious trial and error processes to obtain rendered images with reliable accuracy. In this paper, we propose an error estimation framework for many-light rendering. Our method transforms VPL clustering into stratified sampling combined with confidence intervals, which enables the user to estimate the error due to clustering without the costly computing required to sum the illumination from all the VPLs. Our estimation framework is capable of handling arbitrary BRDFs and is accelerated by using visibility caching, both of which make our method more practical. The experimental results demonstrate that our method can estimate the error much more accurately than the previous clustering method.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.3.3 [computer graphics]: Picture/Image Generation&mdash Display algorithms I.3.7 [computer graphics]: Three-Dimensional graphics and Realism&mdash Raytracing

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Subdivision schemes with optimal bounded curvature near extraordinary vertices

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computer graphics FORUM 2018年第7期37卷 455-467页

作者： Ma, Yue Ma, Weiyin City Univ Hong Kong Dept Mech Engn Hong Kong Hong Kong Peoples R China

We present a novel method to construct subdivision stencils near extraordinary vertices with limit surfaces having optimal bounded curvature at extraordinary positions. With the proposed method, subdivision stencils for newly inserted and updated vertices near extraordinary vertices are first constructed to ensure subdivision with G1 continuity and bounded curvature at extraordinary positions. The remaining degrees of freedom of the constructed subdivision stencils are further used to optimize the eigenbasis functions corresponding to the subsubdominant eigenvalues of the subdivision with respect to G2 continuity constraints. We demonstrate the method by replacing subdivision stencils near extraordinary vertices for Catmull-Clark subdivision and compare the results with the original Catmull-Clark subdivision and previous tuning schemes known with small curvature variation near extraordinary positions. The results show that the proposed method produces subdivision schemes with better or comparable curvature behavior around extraordinary vertices with comparatively simple subdivision stencils.

关键词： CCS Concepts •Computing methodologies → Mesh geometry models Parametric curve and surface models •Applied computing → computer‐aided design

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Reflection and Refraction on Implicit Surfaces

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Journal of computer Science & Technology 2006年第2期21卷 166-172页

作者：胡伟秦开怀王华维李亚峰 Department of Computer Science and Technology Tsinghua University Beijing 100084 P.R. China

Implicit surfaces are often used in computer graphics. They can be easily modeled and rendered, and many objects are composed of them in our daily life. In this paper, based on the concept of virtual objects, a novel method of real-time rendering is presented for reflection and refraction on implicit surface. The method is used to construct virtual objects from real objects quickly, and then render the virtual objects as if they were real objects except for one more step of merging their images with the real objects＇ images. Characteristics of implicit surfaces are used to compute virtual objects effectively and quickly. GPUs （graphics Processing Units） are used to compute virtual vertices quickly and further accelerate the computing and rendering processes. As a result, realistic effects of reflections and refractions on implicit surfaces are rendered in real time.

关键词： reflection refraction implicit surface GPU

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Shadow generation using discretized shadow volume in angular coordinates 11

Shadow generation using discretized shadow volume in angular...

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11th pacific conference on computer graphics and applications

作者： Thakur, K Cheng, FFH Miura, KT Lexmark Int Inc Lexington KY 40550 USA

ISBN: (纸本)0769520286

A technique to improve the performance of the shadow-volume method is presented. This technique does not require (1) extensive edge/edge intersection tests and intersection angle computation in shadow polygon construction, or (2) any ray/shadow-polygon intersection tests during scan-conversion. The first task is achieved by constructing ridge edge (RE) loops, an inexact form of silhouette, instead of the silhouette. The RE loops give us the shadow volume without any expensive computation. The second task is achieved by discretizing the shadow volume into angular spans. The angular spans, which correspond to scan lines, are stored in a lookup table. This lookup table enables us to mark the pixels that are in shadow directly, without the need of performing any ray/shadow-polygon intersection tests. In addition, the shadow on an object is determined on a line-by-line basis instead of a pixel-by-pixel basis. The new technique is efficient enough to achieve real time performance, without any special hardware, while being scalable with scene size.

关键词： computer graphics Hardware Layout Light sources Lighting Optical refraction Performance evaluation Ray tracing Table lookup Testing

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Rendering in object interference detection on conventional graphics workstations

Rendering in object interference detection on conventional g...

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Proceedings of the 1997 5th pacific conference on computer graphics and applications

作者： Baciu, George Wong, Wingo Sai-Keung Hong Kong Univ of Science and Technology Kowloon Hong Kong

Collision detection between complex objects using rasterizing graphics hardware provides a rich ground of exploration for speeding up the interference detection algorithms and computing points of collision. In this article we show that despite the limitations imposed by the current graphics rendering hardware it is still possible to perform collision detection at rendering rates using only conventional graphics hardware without any enhancements.

关键词： computer graphics

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Optimized construction of linear approximations to image data 11

Optimized construction of linear approximations to image dat...

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11th pacific conference on computer graphics and applications

作者： Petrovic, V Kuester, F Univ Calif Irvine Dept Elect Engn & Comp Sci Visualizat & Interact Syst Grp Irvine CA 92697 USA

ISBN: (纸本)0769520286

We present a method for the efficient construction, optimization, and storage of linear approximations to image data. A general simulated annealing-based optimization technique is adapted to the specific problem of optimizing image approximations. A linear approximation is defined by a triangulated subset of the source image pixels and the quality of an approximation may be judged with reference to a computed mean or RMS per-pixel difference between the source image and the approximation. A greedy algorithm for the construction of an initial configuration is described for which the spatial distribution of approximation points reflects the distribution of detail in the image. The approximation is optimized by a sequence of reconfiguration steps chosen according to a simulated annealing process. We outline an efficient implementation of the optimization procedure, explore fast error-recalculation methods, and describe an approximation-compression technique that allows efficient storing, transmission, and viewing of the final approximations. Test results are provided to illustrate the performance of the approximation construction pipeline.

关键词： Approximation algorithms Computational modeling computer errors Encoding Image storage Iterative algorithms Linear approximation Optimization methods Pixel Simulated annealing

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A HIGH-PERFORMANCE PARALLEL COMPUTING SYSTEM FOR IMAGING AND graphics

A HIGH-PERFORMANCE PARALLEL COMPUTING SYSTEM FOR IMAGING AND...

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IEEE pacific RIM CONF ON COMMUNICATIONS computer AND SIGNAL PROCESSING

作者： PARK, HW ALEXANDER, T MOON, SH KIM, Y

ISBN: (纸本)0879426381

UWGSP4 (University of Washington graphics System Processor) consists of four parts: a parallel vector processor, a shared-memory system, an interconnection network, and a graphics subsystem. The parallel vector processor was provided mainly for imaging and general-purpose computing, whereas the main functions of the graphics subsystem are to generate realistic three-dimensional images and to draw the display screen. Among the four parts, the shared memory and the interconnection network were designed to fully support the parallel vector processor and graphics subsystem so as to yield high sustained performance. A discussion is presented of the architecture of UWGSP4, simulated performance figures for several imaging and graphics algorithms, and applications areas.

关键词： computer Systems, Digital

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Illustration watermarks for vector graphics 11

Illustration watermarks for vector graphics

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11th pacific conference on computer graphics and applications

作者： Sonnet, H Isenberg, T Dittmann, J Strothotte, T Otto Von Guericke Univ Dept Simulat & Graph Magdeburg Germany

ISBN: (纸本)0769520286

Digital watermarking is a technique for embedding information into data, such as images, 3D models, or audio files, such that some properties (i. e., security, imperceptibility, robustness) are maintained. While most of the existing watermarking techniques focus on encoding copyright information where security is one of the most important properties, we have developed algorithms for embedding Illustration Watermarks, i. e., content-related annotations for the image. Robustness against common media transformations, high capacity, and blind detection are our aspired properties while security and the usage of secure keys are less important. The medium that we are using for embedding data are 2D vector graphics. We introduce algorithms that change line attributes, introduce new vertices in certain patterns, and replace existing stroke segments by new lines in a stylistic way. Based on the modification they introduce, we categorize our techniques into whether they change the appearance of the image or not and whether the changes are perceivable by the naked eye or not. We demonstrate our techniques with silhouette lines obtained from 3D models. Such line drawings are a very common style utilized in many illustrations, in particular in the medical and technical domain.

关键词： Biomedical imaging Change detection algorithms computer graphics Data security Encoding Image segmentation Information security Robustness Steganography Watermarking

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