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Multi-dimensional dynamic programming in ruled surface fitting

COMPUTER-AIDED DESIGN 2014年 51卷 39-49页

作者： Wang, Charlie C. L. Elber, Gershon Chinese Univ Hong Kong Dept Mech & Automat Engn Shatin Hong Kong Peoples R China Technion Israel Inst Technol Dept Comp Sci IL-32000 Haifa Israel

Ruled surfaces play an important role in many manufacturing and construction applications. In this work, we explore a multi-dimensional dynamic programming based ruled surface fitting scheme to a given freeform rational surface, S. Considering two initial opposite boundaries of S, sampled into a discrete piecewise linear polyline representation, the ruled surface fitting problem is reduced to a pairing-search between the polylines and elevations above the polylines, in the normal directions of S. A four-dimensional dynamic programming solution is sought for the four dimensions prescribed by the two polylines and the two elevation levels along the surface normals. This multi-dimensional dynamic programming is evaluated using highly parallel algorithms running on gpus that ensures the best fit to the sampled data. In order to evaluate the fitting error with respect to S, we derive a scheme to compute a bound from above on the maximal error between a bilinear surface patch (formed by two consecutive point-pairs) and its corresponding surface region on S. Surface-surface composition is employed to extract the corresponding surface region on S to compare against. Finally, the above ruled surface fitting approach is also extended into a discrete algorithm to find the non-isoparametric subdivision curve on S when a discrete recursive piecewise-ruled surface fitting is considered. A five- or seven-dimensional dynamic programming solution is employed towards this end and once again, surface-surface composition is employed to extract the two subdivided patches as tensor products. (C) 2014 Elsevier Ltd. All rights reserved.

关键词： Ruled surface fitting Multi-dimensional dynamic programming Surface-surface composition gpu algorithms

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A multi-gpu real-time dose simulation software framework for lung radiotherapy

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INTERNATIONAL JOURNAL OF COMPUTER ASSISTED RADIOLOGY AND SURGERY 2012年第5期7卷 705-719页

作者： Santhanam, A. P. Min, Y. Neelakkantan, H. Papp, N. Meeks, S. L. Kupelian, P. A. Univ Calif Los Angeles Los Angeles CA 90095 USA Univ Cent Florida Orlando FL 32816 USA MD Anderson Canc Ctr Orlando Orlando FL USA

Medical simulation frameworks facilitate both the preoperative and postoperative analysis of the patient's pathophysical condition. Of particular importance is the simulation of radiation dose delivery for real-time radiotherapy monitoring and retrospective analyses of the patient's treatment. In this paper, a software framework tailored for the development of simulation-based real-time radiation dose monitoring medical applications is discussed. A multi-gpu-based computational framework coupled with inter-process communication methods is introduced for simulating the radiation dose delivery on a deformable 3D volumetric lung model and its real-time visualization. The model deformation and the corresponding dose calculation are allocated among the gpus in a task-specific manner and is performed in a pipelined manner. Radiation dose calculations are computed on two different gpu hardware architectures. The integration of this computational framework with a front-end software layer and back-end patient database repository is also discussed. Real-time simulation of the dose delivered is achieved at once every 120 ms using the proposed framework. With a linear increase in the number of gpu cores, the computational time of the simulation was linearly decreased. The inter-process communication time also improved with an increase in the hardware memory. Variations in the delivered dose and computational speedup for variations in the data dimensions are investigated using D70 and D90 as well as gEUD as metrics for a set of 14 patients. Computational speed-up increased with an increase in the beam dimensions when compared with a CPU-based commercial software while the error in the dose calculation was < 1%. Our analyses show that the framework applied to deformable lung model-based radiotherapy is an effective tool for performing both real-time and retrospective analyses.

关键词： Lung radiotherapy gpu algorithms Dose simulation

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Real-time water waves with wave particles

Real-time water waves with wave particles

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作者： Yuksel, Cem Texas A&M University

学位级别：Ph.D.

This dissertation describes the wave particles technique for simulating water surface waves and two way fluid-object interactions for real-time applications, such as video games. Water exists in various different forms in our environment and it is important to develop necessary technologies to be able to incorporate all these forms in real-time virtual environments. Handling the behavior of large bodies of water, such as an ocean, lake, or pool, has been computationally expensive with traditional techniques even for offline graphics applications, because of the high resolution requirements of these simulations. A significant portion of water behavior for large bodies of water is the surface wave phenomenon. This dissertation discusses how water surface waves can be simulated efficiently and effectively at real-time frame rates using a simple particle system that we call "wave particles." This approach offers a simple, fast, and unconditionally stable solution to wave simulation. Unlike traditional techniques that try to simulate the water body (or its surface) as a whole with numerical techniques, wave particles merely track the deviations of the surface due to waves forming an analytical solution. This allows simulation of seemingly infinite water surfaces, like an open ocean. Both the theory and implementation of wave particles are discussed in great detail. Two-way interactions of floating objects with water is explained, including generation of waves due to object interaction and proper simulation of the effect of water on the object motion. Timing studies show that the method is scalable, allowing simulation of wave interaction with several hundreds of objects at real-time rates.

关键词： wave particles waves real-time simulation fluid-object interaction gpu algorithms Book Thesis

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Fast real-time caustics from height fields

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VISUAL COMPUTER 2009年第5-7期25卷 559-564页

作者： Yuksel, Cem Keyser, John Texas A&M Univ Dept Comp Sci & Engn College Stn TX USA

Caustics are crucial in water rendering, yet they are often neglected in real-time applications due to the demanding computational requirements of the general-purpose caustics computation methods. In this paper we present a two-pass algorithm for caustics computation that is extremely fast and produces high-quality results. Our algorithm is targeted for commonly used height field representations of water and a planar caustic-receiving surface. The underlying theory of our approach is presented along with implementation details and pseudo codes.

关键词： Caustics Real-time water rendering gpu algorithms Height fields

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Real-time Rendering of Large-scale Terrain based on gpu

Real-time Rendering of Large-scale Terrain based on GPU

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4th IEEE Conference on Industrial Electronics and Applications

作者： Zhang, Yanyan Huang, Qitao Han, Junwei Harbin Inst Technol Sch Mechatron Engn Harbin 150006 Heilongjiang Pr Peoples R China

ISBN: (纸本)9781424427994

For efficient visualization, storage and management of massive datasets in current large-scale terrain rendering system, a real-time rendering algorithm of large-scale terrain based on gpu (Graphic Processing Unit) is proposed. The algorithm is an out-of-core supported aggregated LOD (Level of Detail) rendering method and focuses on the use of gpus' ability in the computation and programmability. The two-ratio filtering simplification method and quadtree-based chunk hierarchy are used to generate a simple and regular chunk structure for view-dependent LOD visualization. Based on this structure, a gpu-oriented data compression strategy is given for reducing data transfer bandwidth and storage consumption;a template-based triangle stripification method is used for optimizing visualization efficiency and generating a conforming terrain without cracks. Besides the management strategy of massive datasets which is based on a two-level caching mechanism makes the algorithm breakthrough the hardware limitation and realize the out-of-core rendering. During the typical fly-over for large-scale datasets, a very high frame rate can be guaranteed by the algorithm.

关键词： Terrain rendering gpu algorithms View-dependent level of detail Terrain data compression Out-of-core

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Accelerated Discovery of Discrete M-Clusters/Outliers on the Raster Plane Using Graphical Processing Units

Accelerated Discovery of Discrete M-Clusters/Outliers on the...

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9th International Conference on Computational Science

作者： Trefftz, Christian Szakas, Joseph Majdandzic, Igor Wolffe, Gregory Grand Valley State Univ Sch Comp Allendale MI 49401 USA Univ Maine Comp Informat Syst Dept Augusta GA 04330 USA

ISBN: (纸本)9783642019692

This paper presents two discrete computational geometry algorithms designed for execution on Graphics Processing Units (gpus). The algorithms are parallelized versions of sequential algorithms intended for application in geographical data mining. The first algorithm finds clusters of in points, called m-clusters, in the rasterized plane. The second algorithm complements the first by identifying outliers, those points which are not members of any m-clusters. The use of a raster representation of coordinates provides an ideal data stream environment for efficient gpu utilization. The parallel algorithms have low memory demands, and require only a limited amount of inter-process communication. Initial performance analysis indicates the algorithms are scalable, both in problem size and in the number of seeds, and significantly outperform commercial implementations.

关键词： gpu algorithms Geographical data mining CUDA programming

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Dual scattering approximation for fast multiple scattering in hair

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ACM TRANSACTIONS ON GRAPHICS 2008年第3期27卷 32-1-32-10-0页

作者： Zinke, Arno Yuksel, Cem Weber, Andreas Keyser, John Univ Bonn Inst Informat 2 D-5300 Bonn Germany Texas A&M Univ Dept Comp Sci College Stn TX 77843 USA

When rendering light colored hair, multiple fiber scattering is essential for the right perception of the overall hair color. In this context, we present a novel technique to efficiently approximate multiple fiber scattering for a full head of human hair or a similar fiber based geometry. In contrast to previous ad-hoc approaches, our method relies on the physically accurate concept of the Bidirectional Scattering Distribution Functions and gives physically plausible results with no need for parameter tweaking. We show that complex scattering effects can be approximated very well by using aggressive simplifications based on this theoretical model. When compared to unbiased Monte-Carlo path tracing, our approximations preserve photo-realism in most settings but with rendering times at least two-orders of magnitude lower. Time and space complexity are much lower compared to photon mapping-based techniques and we can even achieve realistic results in real-time on a standard PC with consumer graphics hardware.

关键词： hair rendering multiple scattering gpu algorithms

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Real-time rendering of textures with feature curves

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ACM TRANSACTIONS ON GRAPHICS 2008年第1期27卷 3-1-3-15-0页

作者： Parilov, Evgueni Zorin, Denis NYU New York NY 10003 USA

The standard bilinear interpolation on normal maps results in visual artifacts along sharp features, which are common for surfaces with creases, wrinkles, and dents. In many cases, spatially varying features, like the normals near discontinuity curves, are best represented as functions of the distance to the curve and the position along the curve. For high-quality interactive rendering at arbitrary magnifications, one needs to interpolate the distance field preserving discontinuity curves exactly. We present a real-time, gpu-based method for distance function and distance gradient interpolation which preserves discontinuity feature curves. The feature curves are represented by a set of quadratic Bezier curves, with minimal restrictions on their intersections. We demonstrate how this technique can be used for real-time rendering of complex feature patterns and blending normal maps with procedurally defined profiles near normal discontinuities.

关键词： algorithms human factors performance curvilinear feature rendering distance function gpu algorithms normal mapping resolution independence

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Deep opacity maps

Deep opacity maps

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29th Annual Conference of the European-Association-for-Computer-Graphics

作者： Yuksel, Cem Keyser, John Texas A&M Univ Dept Comp Sci College Stn TX 77843 USA

We present a new method for rapidly computing shadows from semi-transparent objects like hair. Our deep opacity maps method extends the concept of opacity shadow maps by using a depth map to obtain a per pixel distribution of opacity layers. This approach eliminates the layering artifacts of opacity shadow maps and requires far fewer layers to achieve high quality shadow computation. Furthermore, it is faster than the density clustering technique, and produces less noise with comparable shadow quality. We provide qualitative comparisons to these previous methods and give performance results. Our algorithm is easy to implement, faster, and more memory efficient, enabling us to generate high quality hair shadows in real-time using graphics hardware on a standard PC.

关键词： shadow maps semi-transparent shadows hair shadows real-time shadows gpu algorithms

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gpu-accelerated Adaptively Sampled Distance Fields

GPU-accelerated Adaptively Sampled Distance Fields

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IEEE International Conference on Shape Modeling and Applications

作者： Bastos, Thiago Celes, Waldemar Tecgraf - Computer Graphics Technology Group Department of Computer Science PUC-Rio Brazil

ISBN: (纸本)9781424422609

Adaptively Sampled Distance Fields (ADFs) are volumetric shape representations that support a broad range of applications in the areas of computer graphics, computer vision and physics. ADFs are especially beneficial for representing shapes with features at very diverse scales. In this paper, we propose a strategy to represent and reconstruct ADFs on modem graphics hardware (gpus). We employ a 3D hashing scheme to store the underlying data structure and try to balance the tradeoff between memory requirements and reconstruction efficiency. To render ADFs on gpu, we use a general-purpose ray-casting technique based on sphere tracing, which guarantees the reconstruction of fine details. We also present a way to overcome the C-1 discontinuities inherent to ADFs and efficiently reconstruct smooth surface normals across cell boundaries. The effectiveness of our proposal is demonstrated for isosurface rendering and morphing.

关键词： ADFs gpu algorithms implicit surface rendering

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