Fast Ray Tracing Techniques

In the past, ray tracing has been used widely in offline rendering applications since it provided the ability to better capture high quality secondary effects such as reflection, refraction and shadows. Such effects are difficult to produce in a robust, high quality fashion with traditional, real-time rasterization algorithms. Motivated to bring the advantages to ray tracing to real-time applications, researchers have developed better and more efficient algorithms that leverage the current generation of fast, parallel CPU hardware within the past few years. This thesis provides the implementation and design details of a high performance ray tracing solution called ``RTTest'' for standard, desktop CPUs. Background information on various algorithms and acceleration structures are first discussed followed by an introduction to novel techniques used to better accelerate current, core ray tracing techniques. Techniques such as Omni-Directional Packets, Cone Proxy Traversal and Multiple Frustum Traversal are proposed and benchmarked using standard ray tracing scenes. Also, a novel soft shadowing algorithm called Edge Width Soft Shadows is proposed which achieves performance comparable to a single sampled hard shadow approach targeted at real time applications such as games. Finally, additional information on the memory layout, rendering pipeline, shader system and code level optimizations of RTTest are also discussed

Freeform User Interfaces for Graphical Computing

報告番号: 甲15222 ; 学位授与年月日: 2000-03-29 ; 学位の種別: 課程博士 ; 学位の種類: 博士(工学) ; 学位記番号: 博工第4717号 ; 研究科・専攻: 工学系研究科情報工学専

08221 Abstracts Collection -- Geometric Modeling

From May 26 to May 30 2008 the Dagstuhl Seminar 08221 ``Geometric Modeling\u27\u27 was held in the International Conference and Research Center (IBFI), Schloss Dagstuhl. During the seminar, several participants presented their current research, and ongoing work and open problems were discussed. Abstracts of the presentations given during the seminar as well as abstracts of seminar results and ideas are put together in this paper. The first section describes the seminar topics and goals in general. Links to extended abstracts or full papers are provided, if available

Hardware acceleration of photon mapping

PhD ThesisThe quest for realism in computer-generated graphics has yielded a range of algorithmic techniques, the most advanced of which are capable of rendering images at close to photorealistic quality. Due to the realism available, it is now commonplace that computer graphics are used in the creation of movie sequences, architectural renderings, medical imagery and product visualisations. This work concentrates on the photon mapping algorithm [1, 2], a physically based global illumination rendering algorithm. Photon mapping excels in producing highly realistic, physically accurate images. A drawback to photon mapping however is its rendering times, which can be significantly longer than other, albeit less realistic, algorithms. Not surprisingly, this increase in execution time is associated with a high computational cost. This computation is usually performed using the general purpose central processing unit (CPU) of a personal computer (PC), with the algorithm implemented as a software routine. Other options available for processing these algorithms include desktop PC graphics processing units (GPUs) and custom designed acceleration hardware devices. GPUs tend to be efficient when dealing with less realistic rendering solutions such as rasterisation, however with their recent drive towards increased programmability they can also be used to process more realistic algorithms. A drawback to the use of GPUs is that these algorithms often have to be reworked to make optimal use of the limited resources available. There are very few custom hardware devices available for acceleration of the photon mapping algorithm. Ray-tracing is the predecessor to photon mapping, and although not capable of producing the same physical accuracy and therefore realism, there are similarities between the algorithms. There have been several hardware prototypes, and at least one commercial offering, created with the goal of accelerating ray-trace rendering [3]. However, properties making many of these proposals suitable for the acceleration of ray-tracing are not shared by photon mapping. There are even fewer proposals for acceleration of the additional functions found only in photon mapping. All of these approaches to algorithm acceleration offer limited scalability. GPUs are inherently difficult to scale, while many of the custom hardware devices available thus far make use of large processing elements and complex acceleration data structures. In this work we make use of three novel approaches in the design of highly scalable specialised hardware structures for the acceleration of the photon mapping algorithm. Increased scalability is gained through: • The use of a brute-force approach in place of the commonly used smart approach, thus eliminating much data pre-processing, complex data structures and large processing units often required. • The use of Logarithmic Number System (LNS) arithmetic computation, which facilitates a reduction in processing area requirement. • A novel redesign of the photon inclusion test, used within the photon search method of the photon mapping algorithm. This allows an intelligent memory structure to be used for the search. The design uses two hardware structures, both of which accelerate one core rendering function. Renderings produced using field programmable gate array (FPGA) based prototypes are presented, along with details of 90nm synthesised versions of the designs which show that close to an orderof- magnitude speedup over a software implementation is possible. Due to the scalable nature of the design, it is likely that any advantage can be maintained in the face of improving processor speeds. Significantly, due to the brute-force approach adopted, it is possible to eliminate an often-used software acceleration method. This means that the device can interface almost directly to a frontend modelling package, minimising much of the pre-processing required by most other proposals

Accelerating and simulating detected physical interations

The aim of this doctoral thesis is to present a body of work aimed at improving performance and developing new methods for animating physical interactions using simulation in virtual environments. To this end we develop a number of novel parallel collision detection and fracture simulation algorithms. Methods for traversing and constructing bounding volume hierarchies (BVH) on graphics processing units (GPU) have had a wide success. In particular, they have been adopted widely in simulators, libraries and benchmarks as they allow applications to reach new heights in terms of performance. Even with such a development however, a thorough adoption of techniques has not occurred in commercial and practical applications. Due to this, parallel collision detection on GPUs remains a relatively niche problem and a wide number of applications could benefit from a significant boost in proclaimed performance gains. In fracture simulations, explicit surface tracking methods have a good track record of success. In particular they have been adopted thoroughly in 3D modelling and animation software like Houdini [124] as they allow accurate simulation of intricate fracture patterns with complex interactions, which are generated using physical laws. Even so, existing methods can pose restrictions on the geometries of simulated objects. Further, they often have tight dependencies on implicit surfaces (e.g. level sets) for representing cracks and performing cutting to produce rigid-body fragments. Due to these restrictions, catering to various geometries can be a challenge and the memory cost of using implicit surfaces can be detrimental and without guarantee on the preservation of sharp features. We present our work in four main chapters. We first tackle the problem in the accelerating collision detection on the GPU via BVH traversal - one of the most demanding components during collision detection. Secondly, we show the construction of a new representation of the BVH called the ostensibly implicit tree - a layout of nodes in memory which is encoded using the bitwise representation of the number of enclosed objects in the tree (e.g. polygons). Thirdly, we shift paradigm to the task of simulating breaking objects after collision: we show how traditional finite elements can be extended as a way to prevent frequent re-meshing during fracture evolution problems. Finally, we show how the fracture surface–represented as an explicit (e.g. triangulated) surface mesh–is used to generate rigid body fragments using a novel approach to mesh cutting

Doctor of Philosophy

dissertationWhile boundary representations, such as nonuniform rational B-spline (NURBS) surfaces, have traditionally well served the needs of the modeling community, they have not seen widespread adoption among the wider engineering discipline. There is a common perception that NURBS are slow to evaluate and complex to implement. Whereas computer-aided design commonly deals with surfaces, the engineering community must deal with materials that have thickness. Traditional visualization techniques have avoided NURBS, and there has been little cross-talk between the rich spline approximation community and the larger engineering field. Recently there has been a strong desire to marry the modeling and analysis phases of the iterative design cycle, be it in car design, turbulent flow simulation around an airfoil, or lighting design. Research has demonstrated that employing a single representation throughout the cycle has key advantages. Furthermore, novel manufacturing techniques employing heterogeneous materials require the introduction of volumetric modeling representations. There is little question that fields such as scientific visualization and mechanical engineering could benefit from the powerful approximation properties of splines. In this dissertation, we remove several hurdles to the application of NURBS to problems in engineering and demonstrate how their unique properties can be leveraged to solve problems of interest