一种立体光线跟踪的加速算法

基于立体视图相关性和景物对双眼的可见性变化规律提出了一种扫描线分段算法,利用对扫描线的特征分段减少单眼可见景物和景物空白的重复计算,使右图效率明显提高,同时考虑光亮度的视图差异,计算重投影点光亮度的视点相关分量,使立体视图的细微差别得以体现,文中还提出二代光一的间接重投影方法和“标记－视点探测－排序”的坏象素消除法。     

A NEW CONVEX HULL ALGORITHM FOR ANY POLYGON

ＡＮＥＷＣＯＮＶＥＸＨＵＬＬＡＬＧＯＲＩＴＨＭＦＯＲＡＮＹＰＯＬＹＧＯＮＨｕＺｈａｎｑｉＬｉＹｕｐｅｎｇＷａｎｇＪｕｎＱｉａｏＬｅｉＡｂｓｔｒａｃｔＡｎｅｗａｌｇｏｒｉｔｈｍｆｏｒｆｉｎｄｉｎｇｃｏｎｖｅｘｈｕｌｏｆａｐｏｌｙｇｏｎｉｓｐｒｏｐｏｓｅ...     

光线追踪显示体数据的新求交算法

本文就利用光线追踪方法完成的体绘制提出一种新的求交算法，此算法与以前的求交算法有本质上的不同，求交过程不再是相对于ＣＥＬＬ进行求交，而是直接相对于ｘ，ｙ，ｚ族平面直接进行求交，故此算法所需的运算量相以地于其它算法是非常小的，而且可以直接控制求交顺序而无需排序，这样得到的求交结果对于反续的运算是极方便的，由分析求交过程可以方便的得到交点所对应的ＣＥＬＬ标号，这又方便了颜色向量，隐匿因子的积累、结合等     

图像目标外接多边形及凸壳的一种构造方法

对二值图像进行Hough变换后,在(ρ,θ)空间中选取了一组边界对应点,通过计算与这些边界对应点对应的图像空间中直线的交点,构造了图像目标的外接多边形;通过比较相距π/2 rad的投影区间长度是否相等,或区间长度的乘积是否为最小,得到了形状外接正方形和外接最小面积矩形;利用构造形状外接多边形的方法并通过增加边的数目,构造了形状的近似凸壳.实验和理论分析表明,文中算法具有好的抗噪性能和广泛的适用范围.     

基于旋转曲面场景的快速光线跟踪算法

针对旋转曲面场景提出一种基于综合包围盒技术快速光线跟踪算法。根据二次曲线的局部单调性原理,将母线划分成多个单调区间,连接所有单调区间构造一棵二叉树,在光线跟踪阶段对每个单调区间再剖分,得到的子区间作为二叉树的叶子节点,使用综合包围壳方法为每个子区间计算合适的包围壳。实验结果表明该算法对旋转曲面场景逼近程度好,绘制的图形质量高,平均绘制速率比Kajiya传统算法提高40％。     

Ray Coherence Between a Sphere and a Convex Polyhedron

Using the two ray coherence theorems of Ohta and Maekawa the computation time of ray tracing algorithms for scenes of spheres and convex polyhedra can be reduced considerably. This paper presents further theorems which, together with the first two, may enable further reduction in computation time.     

Progressive Hulls for Intersection Applications

Progressive meshes are an established tool for triangle mesh simplification. By suitably adapting the simplification process, progressive hulls can be generated which enclose the original mesh in gradually simpler, nested meshes. We couple progressive hulls with a selective refinement framework and use them in applications involving intersection queries on the mesh. We demonstrate that selectively refinable progressive hulls considerably speed up intersection queries by efficiently locating intersection points on the mesh. Concerning the progressive hull construction, we propose a new formula for assigning edge collapse priorities that significantly accelerates the simplification process, and enhance the existing algorithm with several conditions aimed at producing higher quality hulls. Using progressive hulls has the added advantage that they can be used instead of the enclosed object when a lower resolution of display can be tolerated, thus speeding up the rendering process. ACM CSS: I.3.3 Computer Graphics—Picture/Image Generation, I.3.5 Computer Graphics—Computational Geometry and Object Modeling, I.3.7 Computer Graphics—Three‐Dimensional Graphics and Realism     

Stochastic Ray Tracing Using SIMD Processor Arrays

Stochastic ray tracing is one of the most elegant methods for anti-aliasing and for generating such phenomena as soft shadows, fuzzy reflections, depth of field, and motion blur, which are difficult to accomplish with the conventional ray-tracing algorithm. Unfortunately, it makes use of stochastic sampling, which requires more than one sample for each pixel. One possible way to speed up ray tracing is to explore the inherent parallelism of the algorithm. In the past few years, the major focus of parallel ray-tracing research has been on the use of MIMD architectures. Although SIMD architectures may be ideal for ray tracing simple scenes, they have been thought unsuitable for ray tracing complex scenes. However, by using scene coherence, we have found that stochastic ray tracing using SIMD processor arrays can be as efficient as most of the existing MIMD ray-tracing algorithms and more cost effective.     

DGPSL：A DISTRIBUTED GRAPHICS LIBRARY

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Ray Specialized Contraction on Bounding Volume Hierarchies

In this paper we propose a simple but effective method to modify a BVH based on ray distribution for improved ray tracing performance. Our method starts with an initial BVH generated by any state‐of‐the‐art offline algorithm. Then by traversing a small set of sample rays we collect statistics at each node of the BVH. Finally, a simple but ultra‐fast BVH contraction algorithm modifies the initial binary BVH to a multi‐way BVH. The overall acceleration for ray‐primitive testing is about 25% for incoherent diffuse rays and 30% for shadow rays, which is significant as a data structure optimization. Similar results are also presented for packet ray tracing, and for Quad‐BVHs the improvement is 10% to 15%. The approach has the advantages of being simple, and compatible with almost any existing BVH and ray tracing techniques, and it require very little extra work to generate the modified tree.     

Efficient CPU‐based Volume Ray Tracing Techniques

Recent research on high‐performance ray tracing has achieved real‐time performance even for highly complex surface models already on a single PC. In this report, we provide an overview of techniques for extending real‐time ray tracing also to interactive volume rendering. We review fast rendering techniques for different volume representations and rendering modes in a variety of computing environments. The physically‐based rendering approach of ray tracing enables high image quality and allows for easily mixing surface, volume and other primitives in a scene, while fully accounting for all of their optical interactions. We present optimized implementations and discuss the use of upcoming high‐performance processors for volume ray tracing.     

Higher Order Ray Marching

Rendering participating media is still a challenging and time consuming task. In such media light interacts at every differential point of its path. Several rendering algorithms are based on ray marching: dividing the path of light into segments and calculating interactions at each of them. In this work, we revisit and analyze ray marching both as a quadrature integrator and as an initial value problem solver, and apply higher order adaptive solvers that ensure several interesting properties, such as faster convergence, adaptiveness to the mathematical definition of light transport and robustness to singularities. We compare several numerical methods, including standard ray marching and Monte Carlo integration, and illustrate the benefits of different solvers for a variety of scenes. Any participating media rendering algorithm that is based on ray marching may benefit from the application of our approach by reducing the number of needed samples (and therefore, rendering time) and increasing accuracy.     

InK‐Compact: In‐Kernel Stream Compaction and Its Application to Multi‐Kernel Data Visualization on General‐Purpose GPUs

Stream compaction is an important parallel computing primitive that produces a reduced (compacted) output stream consisting of only valid elements from an input stream containing both invalid and valid elements. Computing on this compacted stream rather than the mixed input stream leads to improvements in performance, load balancing and memory footprint. Stream compaction has numerous applications in a wide range of domains: e.g. deferred shading, isosurface extraction and surface voxelization in computer graphics and visualization. We present a novel In‐Kernel stream compaction method, where compaction is completed before leaving an operating kernel. This contrasts with conventional parallel compaction methods that require leaving the kernel and running a prefix sum kernel followed by a scatter kernel. We apply our compaction methods to ray‐tracing‐based visualization of volumetric data. We demonstrate that the proposed In‐Kernel compaction outperforms the standard out‐of‐kernel Thrust parallel‐scan method for performing stream compaction in this real‐world application. For the data visualization, we also propose a novel multi‐kernel ray‐tracing pipeline for increased thread coherency and show that it outperforms a conventional single‐kernel approach.     

The State of the Art in Interactive Global Illumination

The interaction of light and matter in the world surrounding us is of striking complexity and beauty. Since the very beginning of computer graphics, adequate modelling of these processes and efficient computation is an intensively studied research topic and still not a solved problem. The inherent complexity stems from the underlying physical processes as well as the global nature of the interactions that let light travel within a scene. This paper reviews the state of the art in interactive global illumination (GI) computation, i.e., methods that generate an image of a virtual scene in less than 1 s with an as exact as possible, or plausible, solution to the light transport. Additionally, the theoretical background and attempts to classify the broad field of methods are described. The strengths and weaknesses of different approaches, when applied to the different visual phenomena, arising from light interaction are compared and discussed. Finally, the paper concludes by highlighting design patterns for interactive GI and a list of open problems.